Sea level has a strong seasonal signal. The annual variability is less than the daily changes associated with tidal forcing in most locations, but still can be on the order of 5-10 cm (maximum values about 15 cm).

The causes of the seasonal fluctuations are mostly associated with seasonal changes in wind intensity and patterns, changes in temperature that relate to thermal expansion, and in salinity (haline contraction) and river discharge fluctuations. The annual sea level cycle is only partially related to ice melt and this effect tends to be quite local.

The largest sea level seasonal cycles are associated with areas in the vicinity of large rivers with strong seasonal cycles (e.g., Bay of Bengal). Also, there is a lot of spatial variability in the seasonal cycle with the northern hemisphere having a larger signal (likely caused by the stronger seasonality in wind patterns).

An example of the seasonal cycle can be seen in the monthly data from the Permanent Service for Mean Sea Level (PSMSL) for Woods Hole, MA (USA) (in m offset to avoid negative values in the PSMSL database). The monthly data shows strong seasonal variability and also a clear trend. As the data is monthly averaged, the tidal oscillations are filtered out. Most sea level rise graphs tend to use annual data and thus the seasonal information is not included.


In January the Intertropical Convergence Zone shifts to south of the equator. And the Subtropical High Pressure Belt moves into areas of Venezuela, which leaves it dry. I am guessing this from a study of principles of world geography and climatology; I don't live in Venezuela though.


Could parallel rivers flow in opposite directions?

One of my favorites: The Columbia and Kootenay rivers. The Kootenay River initially flows southeast, parallel to the initial northwest flow of the Columbia River. The Kootenay passes within 2 kilometers of Columbia Lake, the source of the Columbia.

Source: https://en.wikipedia.org/wiki/File:Kootenay_River_Map.png


What is the effect of rising sea level on measurements of elevation?

Elevation can be measured against a tidal datum, in which case it is usually tied to some historic mean, or against a geodetic datum, which is statically defined.

Tidal datums, of which there are many flavours, are only useful locally and, as you thought, they drift over time. Here's what NOAA says:

  Tidal datums are used as references to measure local water levels and should not be extended into areas having differing oceanographic characteristics without substantiating measurements. In order that they may be recovered when needed, such datums are referenced to fixed points known as bench marks. Tidal datums are also the basis for establishing privately owned land, state owned land, territorial sea, exclusive economic zone, and high seas boundaries.

For large (continental or global) areas of interest, you need geodetic datums.

In the UK, Ordnance Datum Newlyn was defined in 1956 as the mean sea-level at Newlyn, Cornwall, between 1915 and 1921. In the US, the North American Vertical Datum of 1988 prevails today (though several others are in use). It was pegged to the local mean sea level height at Rimouski, Quebec, Canada.

There are two types of reference surface, the earth's equivalent of the celestial ones you mentioned in your question: the geoid, and ellipsoids. The geoid is the surprisingly lumpy shape that the ocean surface would take in the absence of factors like tides. It can be measured with gravity anomalies, e.g. by GRACE. Since it's a natural surface, you could think of the geoid as the earth's absolute datum. Ellipsoids, on the other hand, are models of the geoid and, as mathematical surfaces, are smooth.

As shown in the figure, GPS uses the World Geodetic System of 1984 for its measurements, so elevation is measured against its ellipsoid. So one must correct GPS elevations  to this orthometric height (height above the geoid).

If you want to read more, this tutorial on datums from NOAA is pretty fantastic. And here's a nice piece on the height of Everest, with respect to various datums.

Image: Judson L. Ahern, University of Oklahoma, via Federal Geographic Data Committee.


Is it possible to detect Coriolis effect using a Wind Rose?

Yes, your figure is correct: in the mid-latitudes we have cyclones and anticyclones. They can't exist on equator because the Coriolis force there is too small to keep them stable. But the cyclones or anticyclones are present all around your country and their effect cancels each other. So, you can't determine the presence of Coriolis force. Otherwise, the effect of spining anticyclones and cyclones isn't specific to your country, but is (as previously stated) present over mid-latitudes. Also, the Coriolis effect isn't acting on microswirls because the Coriolis parameter is so small (due to too slow Earth's rotation).


Non-invasive techniques to find rock composition

You are looking for a portable XRF.

It does (almost) exactly what you said. It sends electromagnetic radiation to the rock (X-rays), which excites electrons in the atoms and when they bounce back they return X-ray of different energies which are detected by the instrument. It looks like this, for example:

Using the different peaks you can figure out what the rock is made of.

This is not as good as lab-based XRF, but it's so easy to use it's now standard practice for exploration and mining geologists to use it.

Note that this will only give you surface information. It analyses what it can see. If you want to know what is inside the rock, you have to drill or break it.

If you want to know what is inside the rock without breaking it, you can use a CT scanner, but it only gives information on density. Inferring what the material is based on its density can be a challenging task and it is made easier if you have pre-existing information on what it could be. There are no portable CT scanners however (at least not hand-held). They can me mounted on trucks though.

There are other methods, such as infrared, Raman, LIBS, etc etc.

The Mars Curiosity Rover has quite a lot of those instruments on board. It is essentially a semi-automated geologist exploring another planet.


Why do some earthquakes and volcanoes occur within plates?

Crustal plates are not homogeneous, uniformly continuous rock masses with uniform stresses. They are a mixture of rock types with variable stresses and stress concentrations. They are also discontinuous.

There are fault zones within plates. Some faults are active & others inactive.  When movement occurs along an active fault, usually due to in-plate localized stresses, an in-plate earthquake will occur.

Concerning in-plate volcanoes. These are due to geological hotspots. These are,

  thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle.[citation needed] Their position on the Earth's surface is independent of tectonic plate boundaries. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths.


What causes this white coloration of the ground in Gilf-Kebir?

The white areas appear to be formed on the edge of elevated parts of the landscape and in low-lying flat areas. You can see this if you use Google Earth and looking at the elevation profiles along paths you sketch across the landscape. They don't appear to form at a particular elevation or other pattern that would indicate they are bedrock outcrops.

I think the most likely possibility is that they are caliche deposits (calcium-carbonate cemented sediments), formed as water ran off of higher elevations, mobilizing calcium and evaporating to cause calcite saturation. They could be halite but I would expect more extensive deposits in the broader drainage areas if they were salt. They could have formed under wetter climate conditions. If you look at 23 degrees 14.053' North, 24 degrees 25.22' East, you can see deposits being covered by sand dunes.


How do spectral methods work in the context of numerical weather prediction models?

Presume that the atmosphere can be modeled with waves of different frequencies. Therefore, the atmosphere can be written as a series of sine and cosine functions with different frequencies and coefficients. Consider the linear advection equation: $$\frac{\partial u}{\partial t}= -c \frac{\partial u}{\partial x}$$

Consider the assumption that $u$ can be modeled as $$u=\sum^\infty_{|n|=0} A_n(t)\exp(i\omega_n x) $$ But since we have limited computational resources, $$u=\sum^N_{|n|=0} A_n(t)\exp(i\omega_n x) $$ Therefore, our advection equation becomes $$\sum^\infty_{|n|=0} \frac{d A_n(t)}{dt}\exp(i\omega_n x)=-c\sum^\infty_{|n|=0} i \omega_n A_n(t)\exp(i\omega_n x) $$

If we integrate this equation and leverage the orthogonal properties of sine and cosine, $$\int^L_0 \sum^\infty_{|n|=0} \frac{d A_n(t)}{dt}\exp(i\omega_n x)\exp(i\omega_m x)dx=-c\int^L_0 \sum^\infty_{|n|=0} i \omega_n A_n(t)\exp(i\omega_n x)\exp(i\omega_m x)dx$$ Then the summation notation can be removed. $$\frac{d A_m(t)}{dt}=-ic \omega_m A_m(t)$$ Now this can be solved analytically, and as such we do have an analytic solution to the advection equation, but what we can do to model this numerically, is combine the finite difference notation and the spectral solution to numerically integrate the advection equation.

For example, $$u_{n+1}= u_n -c\Delta t\sum^\infty_{|l|=0} i \omega_l A_l(t)\exp(i\omega_l x) $$

So to summarize,

Assume that the variable can be expressed as a sum of basis functions, commonly sine and cosine functions.
Create a truncated series (fourier series), creating an analytic expression for said quantity.
Evaluate the derivative of the truncated series, and replace the derivative (often computed with finite difference approximations) with the analytic representation of the derivative.
Numerically integrate in time.

Now there are plenty of limitations, such as the nonlinear version of that equation. If I had my notes on hand, then I could address those problems more. I'll edit this when I can. Also, model physics cannot be computed in spectral space, so there has to be conversion from spectral to physical space and vice-versa.

I'll check my notes and correct any errors I can find later.


Why are weather kites no longer used (much) operationally?

Most data we collect about weather is done regularly and for all altitudes of the troposphere.  Kites, though, are at the mercy of the weather and do not fly high enough.  So when there is ice or snow or other meteorological conditions that don't allow a kite to fly, you get no data.  We now use methods to measure the weather that don't break in bad weather.  The answer to your question is succinctly put in this NOAA webpage where they state these difficulties with kites:

The average altitude reached was only about 3 km.
Data could not be evaluated until after the kite was reeled in...
Observations could only be taken in good weather with winds neither too light or too strong.
There was danger of the kite breaking away and endangering lives and property.

In the 1940s, weather balloons were being released and could gather an entire profile of data in all weather conditions.  This is far superior to a kite.  That being said, some people do still use kites: High-Flying Science, with Strings Attached.


References for moving and nested grids in models

Book:

Shyy W, Udaykumar HS, Rao MM, Smith RW. Computational Fluid Dynamics with Moving Boundaries. Taylor& Francis: London, 1996.

Some relevant papers:

Jin C, Xu K. A unified moving grid gas-kinetic method in Eulerian space for viscous flow comnputation. Journal of Computational Physics 2007; 222:155–175.

Hirt CW, Amsden AA, Cook JL. An arbitrary Lagrangian–Eulerian computing method for all flow speeds. Journal of Computational Physics 1997; 135:203–216.

Piggott M, Pain C, Gorman G, Power P, Goddard A. h, r, and hr adaptivity with applications in numerical ocean modeling. Ocean Modelling 2005; 10:95–113

HuangWZ, Ren Y, Russell RD.Moving mesh methods based on moving mesh partial differential equations. Journal of Computational Physics 1994; 113:279–290.

Miller K, Miller RN. Moving finite element. SIAM Journal of Numerical Analysis 1981; 18:1019–1032.

Dorfi EA, Drury LO. Simple adaptive grids for 1-D initial value problems. Journal of Computational Physics 1987; 69:175–195.

Tang T. Moving mesh methods for computational fluid dynamics. Contemporary Mathematics 2005; 383:141–174.

Tang H, Tang T. Adaptive mesh methods for one- and two-dimensional hyperbolic conservation laws. SIAM Journal of Numerical Analysis 2003; 41(2):487–515.

Tang H, Tang T. Multi-dimensional moving mesh method for shock computations. Contemporary Mathematics 2003; 330:169–183.

Adaptive grid concepts have been applied to the Princeton Ocean Model (POM).

Original Paper for POM:

Blumberg, A. F. and G. L. Mellor, A description of a three-dimensional coastal ocean circulation model. Three-Dimensional Coastal ocean Models, edited by N. Heaps, 208 pp., American Geophysical Union., 1987

With adaptive mesh:

Hofmeister, Richard, Hans Burchard, and Jean-Marie Beckers. "Non-uniform adaptive vertical grids for 3D numerical ocean models." Ocean Modelling 33.1 (2010): 70-86.


seismic wave detection standing at the epicenter

A person would not detect much else than the surface waves (Love and Rayleigh waves). The later body waves phases are of very low amplitude and are only detected by a sensitive seismometer. Also, at a short offset, it is often hard to pick later phases, even if they occur. There is a critical angle for seismic refraction, but not for reflection. 0-offset reflection originates just beneath the source.

The core-mantle boundary represent a large change in elastic properties, so some energy will bounce back to the surface. We call these phases PcP, ScP and ScS phases (Pressure-core-Pressure etc). The PcP is the reflected P-wave and ScS is the reflected S-wave. The ScP wave is an interesting phenomena, as it's formed as a part of the energy in the S-wave is converted into a P wave and reflected. There are also higher orders of seismic wave phases that can be detected (or modelled in synthetic seismograms) near the epicenter, the PcP2 and ScS2 e.g. (not shown in figure). The PKiKP is a reflection from the inner core.

The travel time diagram gives a rather good idea of when to expect seismic phases at different distances from the earthquake. The distance is in degrees, so 180$^\circ$ is on the opposite side of the planet. Note how the core shields all direct shear waves, that is why we know that the outer core is fluid.


What are baroclinic and barotropic waves?

Barotropic flows are those for which the fluid density $\rho$ depends on pressure $p$ only, i.e. $\rho = \rho(p)$. For example, constant density, isothermal, and isentropic flows are barotropic. Baroclinic flows are flows that are not barotropic. In this case the fluid density depends on pressure AND temperature, salinity, constituent concentration. Heavy fluid sitting adjacent to lighter fluid will sink and rise, respectively.

  These flows are said to be baroclinic, meaning pressure breaking.

Consider the two fluid elements below. In the barotropic case, lines of constant $p$ are parallel to lines of constant $\rho$  so there is no mechanism to generate vorticity. On the other hand, in the baroclinic case, the lines of constant $p$ and $\rho$ are not parallel. The latter arrangement give rise to changes in vorticity $\vec{\omega}$ and circulation because the net pressure force no longer passes through the center of mass of the fluid element.

Seen another way, take a look at the vorticity equation with density variation:

$$\frac{D\vec{\omega}}{Dt} = (\vec{\omega}\cdot \nabla)\vec{u} + \frac{1}{\rho^2}(\nabla \rho \times \nabla p)$$

The cross term on the right hand side is the baroclinic torque. When it is zero the flow is barotropic whereas if it is nonzero the flow is baroclinic.

When applied to waves in the Ocean the result is that barotropic relates to waves propagating at the ocean surface. Baroclinic relates to waves propagating along density surfaces in the interior of the ocean (or internal waves).

One good example is the surface tide and the internal tide. As the surface tide (regular tide) sweeps around the main oceanic basins, it rubs against the ocean floor giving rise to internal tides. The former are called barotropic tides, whereas the latter are called baroclinic tides.

References:

P. Kundu, Fluid Mechanics

B. Sutherland, Internal Gravity waves


Short answer: humidity is not a proxy for rain starting and no, it does not start raining automatically when 100% humidity is reached (haze or clouds can form though).  The onset of rain is dependent on many things including humidity, but a specific value of humidity is not a sufficient condition for rain.

Water vapor is a gas and invisible.  The amount of water vapor in the air can be expressed as relative humidity (RH) which is the ratio of water vapor pressure ($e$) and saturation water vapor pressure ($e_s$).  Saturation vapor pressure is the partial pressure of vapor when evaporation and condensation rates are equal, represented by RH=100%.  When RH > 100% net condensation occurs, but water has its own ideas.

In a mixture of pure dry air and water vapor, water will not condense until around 400% RH.  Reasons for this are a bit complicated but it has to do with very small droplets being more likely to evaporate as their curvature is very large (Kelvin effect, saturation vapor pressure is higher over curved surfaces than flat ones).  Luckily for us, our atmosphere is not pure air but has small particulates suspended in it (aerosols).  Some of these aerosols are classed as cloud condensation nuclei (CCN) and enable droplet formation at lower relative humidities.  These work by forming a solute in water increasing the energy needed to break bonds and evaporate the water (Raoult's_law)

The combined interaction of these are described by Köhler theory and describe droplet growth in terms of drop size, solute and supersaturation (RH-100%).  In a nutshell, there is a critical drop size below which drop size decreases for decreasing supersaturation and above which drop size increases for decreasing supersaturation.  The critical supersaturation is the supersaturation needed to attain the critical drop size, and is generally small (e.g. 0.3% supersaturation).

Droplets below the critical size are 'haze drops' and these make up the haze you see on very humid days.  Drops that reach the critical size can continue to grow to become cloud drops.  The condensed water is carried in the air but is no longer water vapor and is not part of relative humidity (but does contribute to the parcel density)

So... when does it rain?

It rains when water vapor is in the presence of CCN, driven to a supersaturation causing growth to the critical drop size (on the order of $\mu$m) and continuing to grow to cloud drops and further to the much bigger drop sizes that make up drizzle (100-300 $\mu$m)and rain drops(mm), a process that takes around 40 minutes.  Drops will grow until the updraft can no longer support their mass and then they fall from the cloud as rain.

Your question asks at what humidity does it rain, but what surface humidity determines is how high the cloud bases are.  When the dew point depression (the difference between temperature and dew point) is high, the cloud bases will be higher than when the dew point depression is small.  As air rises it cools, and at some point 100% RH is attained.  If there is forcing for vertical ascent, parcels can rise to this height and then to a height where they freely convect due to decreased parcel density caused by the release of energy during condensation (see: CAPE).

So far to have rain we've needed water vapor (but not at 100% at the surface), aerosols to aid condensation (CCN) and a way to cool the air to reach 100% RH via lifting.  It is these three things -- moisture, aerosols and cooling, that we need for a rain storm.  We can have 100% RH days that are just hazy or foggy that do not rain and we can have days with mextremely little RH (e.g. deserts) that result in little rainstorms or large severe storms.  We also have storms we call 'elevated convection' that are completely disconnected from surface conditions and when these storms cause rain is not related to surface humidity at all.

If you are looking for a magic trigger for rain, your closest bet will be looking at temperature, dew point and the height parcels need to attain to freely convect (LFC).  If there is forcing for parcels to get that high and instability above, then rain is a good bet.  Forcing for lift can be anything from convergence along a boundary (sea breeze, cold front, outflow from another storm), orographic lifting (mountains, hills), thermally or dynamically forced.

To address your specific concerns:

  Water vapor is the gaseous state of water and is invisible

    Invisible to me would mean that clouds are excluded from humidity.

Correct, clouds are not part of humidity, they are suspended liquid water drops, usually condensed onto a solute of some kind.

  Absolute humidity is the total mass of water vapor present in a given volume of air.

    That again makes me think a cloud must be included.

Water vapor contributes to humidity but water vapor does not include liquid water.  Cloud water, ice, snow, rain, grapple, hail all contribute to the total mass of a volume of air, but are not humidity.

  The humidity is affected by winds and by rainfall.

    Rainfall certainly decreases humidity, but it is not stated at what percentage it starts to rain.

Humidity will increase during a rainstorm as rain and puddles evaporate.  Temperature will decrease toward the wet bulb temperature.  As noted in the answer, there isn't a magic number of %humidity that causes rain to start.


Those are bathymetric survey tracks.

The survey artifacts are very straight and regular in character, compared to geological features. What you're seeing is an increased level of detail along the survey line, which contrasts with the relatively smooth background model.

I labeled some of the features in this answer to a related question:

NOAA Reference: Did I find the lost underwater civilization of Atlantis?


Definitions of tidal harmonic constituents...?

The explanation of all the tidal constituents is pretty complex because of the interactions between the different frequencies involved. The harmonic analysis is an expansion of the Equilibrium Theory of Tides into a set of harmonic terms. The list of relevant periods includes:

the lunar day (period of lunar rotation), 24.84 mean solar hours.
the sidereal month (period of lunar declination), 27.32 mean solar days.
the tropical year (period of solar declination), 365.24 mean solar days.
the period of the lunar perigee, 8.85 years (1 year = 365.2421988 days).
the period of the lunar node, 18.61 years.
the period of the solar perihelion, 20940 years.

The frequency of any tidal constituent can be computed by a combination of small numbers that multiply each of the periods (usually they are expressed as speeds, e.g., degrees per mean solar hour) above. The most complete algebraic expansion of the constituents was produced by Doodson in 1921. The set of small numbers are called Doodson numbers and represent the importance of each of the period in the specific constituent.

For instance, the set of Doodson numbers for the $M_2$ is (2,0,0,0,0,0), with the ”2” referring to "twice per lunar day" and the rest of the terms are zero (no influence). This is expected as the $M_2$ represents the passage of the same point on Earth through the "tidal bulge", created by the tidal forces, twice in a lunar day. The set of Doodson numbers for the $O_1$ is (1,-1,0,0,0,0), which represents 1 cycle/lunar day minus 1 cycle/tropical month. This is the result of the inclination between the Earth's axis and the Moon's orbit that causes the "tidal bulge" to be offset from the Equator and thus a point on Earth will experience one single absolute maximum per day.

The explanation of the lesser tidal constituents become rather tricky as the combination of Doodson numbers increases. For instance, $MSN_2$ is a combination of lunar, solar, and nodal influences and has a set of Doodson numbers of (2,3,-2,-1,0,0) making the interpretation rather complex.

While a list of origins of the constituents can be found (e.g., Table 4.1 in Pugh, 1996), ultimately it is simpler to try to understand each constituent as the result of a harmonic (~ Fourier expansion) decomposition, rather than a complex interaction between the bodies and their periods.

A few good books dealing with the analysis of tides are:

Pugh, D. T. (1996). Tides, surges and mean sea-level. John Wiley & Sons Ltd. (check Table 4.1 for a list of constituents and their origin).
Godin, G. (1972). The analysis of tides, 264 pp. University of Toronto.
Kowalik, Z., & Luick, J. (2013). The Oceanography of Tides. University of Alaska Fairbanks.


Can Ozone (O$_3$) form in a vacuum and if so can it deflect solar radiation

If this would work, would $O_3$ free-floating in very loose clouds in space help deflect solar radiation at all?

No, for many reasons:

Your cloud will disperse. That's what gases do in vacuum.
And then the dispersed cloud will get swept away by radiation pressure and the solar wind.
So you'll have to be constantly replenishing your loose cloud.
There are 3 billion metric tons of ozone in the Earth's atmosphere.
Compare that huge quantity with the 380.95 kilograms of lunar rock brought back by the six Apollo missions that landed on the Moon, or the 0.401 kilograms retrieved by Russia's unmanned Luna missions.

The engineering feat you are proposing is more than six orders of magnitude larger than anything humankind has done with regard to space. The Apollo program peak cost was a bit less than 5% of the total US federal budget. A factor of ten (one order of magnitude) larger scope would be far beyond the capabilities of the US government. Even with the entire world pitching in, a two order of magnitude increase would be nearly impossible. A six order of magnitude increase is economically impossible.

The worst part: Even if successful, your cloud won't do much. Oxygen in all its forms (atomic oxygen, molecular oxygen, and ozone) is nicely transparent in the frequency range where sunlight is at its peak. Evidence: You can see the stars on a clear night.


What determines the spatial resolution of a study?

It sounds to me like the reviewer is fixated on a 'rule' they encountered in grad school, but the rule ignores some real-world nuance (as rules do).

Quick caveat: my answer isn't definitive, it's more of an opinion, but it was too long for a comment.

It seems intuitively true that some phenomena just are smooth, so the resolution of the data is not the limiting factor in an analysis of resolution. I'm thinking of things like maps of average seasonal air temperature (say). Certainly, you can combine that with higher-resolution data and still claim to have a high-resolution analysis.

Other data may not be implicitly smooth, but it's interesting to aggregate the data for the purposes of generalization.So the quality of academic institutions obviously varies on a per-institution basis (or per teacher, if you want to get silly about it), but it would be crazy to interpolate data like that and, since it's reasonable to think there might be national-level influence (e.g. in funding for education), it only makes sense to aggregate it that way. Again, I think it's reasonable to argue that you can combine data like this with higher-resolution data and have a high-resolution analysis overall.

Still other data may simply be oversmoothed, or smoothed on the wrong basis. Temperature data by country, or geological data on a 100-km grid... Then I'd say those are limiting the resolution of any analysis you do.

In conclusion...

I can't think offhand of a way to formalize all this, and don't know of any research around it (though I'd bet on its existence). Assuming you don't want to go down the research rabbit hole, or have a protracted argument with the reviewer, my advice is to respond to the objection by using more specific language. Instead of generalizing, specify the resolutions of the various datasets involved and mention where it might be possible to improve the resolution.


How can I tell if a rock is really petrified wood?

I don't think there is a really conclusive absolute test one can carry out without further preparations. In the case of a permineralised fossil, this would probably require thin sectioning and close examination to see if any cellular structure diagnostic of wood remains. Overall I'd think though that if it looks like wood and has been replaced by minerals, it probably is fossilised wood. However, you say  you found it in the desert, which perhaps could mean it is some kind of sub-fossil or mummified wood.

The first thing to do would be the standard mineralogy tests to attempt to find out which mineral(s) replaced the wood.


Calculating error in measuring geomagnetic Anomalies using IGRF

The key point here is that both theoretical models quoted - IGRF or WMM - are of the field from the Earth's core only, and only the largest scale parts of it at that. Only the WMM provides an error estimate with these values (as described above), and that error is a combination of "commission errors" from the approximation of the model to reality, and "omission errors" from various magnetic field sources which are not included in the model.

To calculate a magnetic anomaly (usually considered the field from the Earth's crust) you would remove all the other known field sources from the observed field:

  anomaly field = observed field - (core field + external fields)


Does the geothermal activity influence the climate in Iceland?

Since micro climates of a location are mostly based on temperature and precipitation patterns, I would suggest that yes, if focusing on precipitation alone, one would expect rising heat from geothermal activity off the surface as a variable to affect the formation and release of precipitation. But one would have to check what part of the island geothermal activity was highest as the jetstream would drag weather west to east if nearby, and given that it is a small island, may not record such an occurrence as a significant effect from the rising heat available around Iceland. I did find this article which is somewhat supportable of a heat increase around Iceland due to geothermal activity > Douglass/Patel and Knox, 2005. GEOPHYSICAL RESEARCH LETTERS, VOL. 32 https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2004GL021816


Does finer input data lead to a better model accuracy?

My experience with the WRF is in tropical cyclone simulation, but here are some things to consider:

Smaller scale information might already be resolved in your higher resolution initial conditions, improving the spin-up time of effects you are trying to model
I believe the ECMWF resolution has been statistically downscaled from a 0.75 degree dataset, I might be wrong on that one though. That would mean that your 0.25 degree is just some interpolated data
Some models perform better than others in specific regions
Higher resolution is not better if your parameterization is wrong
You can find caveats of specific datasets here: PSD Gridded Climate Datasets.


No, it is not undefined.

A relative humidity of 100% refers to cases in which the atmosphere holds as much water, as the temperature would allow. The term "dry air" denotes the fraction of the air not contaning any water vapor (or explicitly not any water molecules). Dry air is therefore never negligible in clouds.

The saturation vapor pressure over a plane water surface can be calculated by the Magnus formula (which is an empirical approximation to the Clausius-Clapeyron-equation valid in a temperature range from -45°C to 60°C):

$E_{H_2O}(\vartheta)=6.112hPa \cdot exp{\frac{17.62 \cdot \vartheta}{243.15 ^\circ C + \vartheta}} $,

where $\vartheta$ is the temperature in °C.

The water vapor mixing ration $r$ itself is calculated by:

$r=\frac{0.622e}{p-e}$,

where $p$ is the air pressure and $e$ is the water vapor pressure. In case of a cloud you equate $e$ and $E_{H_2O}(\vartheta)$, since the relative humidity is defined as:

$r.H.=\frac{e}{E_{H_2O} (\vartheta)}$

As a sidenote: Oversaturation in clouds may occur frequently but is usually smaller then 1%. For back-of-the-envelope-calculation this should be sufficient.

Please note, that different text books use diffent symbols for $e, E, ...$


Are there any studies comparing different climate models on how well they've forecasted the climate in the past?

Yes. The biggest and broadest are the Palaeoclimate Modelling Intercomparison Projects (PMIP), which are the past-climate equivalent of the Climate Model Intercomparison Projects (CMIP).

The latest is PMIP3. It includes many of the same models that were used in CMIP5, as well as other models that are more focussed on representing past climates. The "overview" link on the PMIP3 page gives an indication of what the project covers, including experiments into the impacts of climate forcings, as well as benchmarking and comparison of models (e.g. quantitative and qualitative assessments of model performance over past climates).


Seismic dispersion: What does it really mean and what causes it?

Frequency- or wavelength-dependent are indeed equally valid terms but frequency is in practice more measurable than wavelength, so much so that seismic wavelength is calculated not measured. Dispersion is caused by material density, the material the waves pass through will, depending on density, pass certain waves, and wavelengths of those waves, better than other waves and wavelengths.

Describing my visualisation of the effect is difficult, the best way to look at the effect is to find seismic traces of the same earthquake from various ranges. This will show the different wave fronts spreading out as they travel. This is largely due to their compatibility with the material they pass through. I find it comparable to structural resonance there are frequencies that interact well with the rock they're travelling through, they get a boost, and there are those that interact less well, they get held back by the material they're travelling through.


If we could green the Sahara, would it be able to sustain itself?

The biggest detriment to keeping deserts green is of course water. With rainfall in the desert limited, afforestation is a tricky and potentially dangerous thing to do. China tried this for decades with afforestation efforts, planting billions of trees in steppe regions of China and Mongolia, only to later worsen because the trees consumed too much ground water and lowered the water table.

On the other hand, trees behave like humidifiers, the little moisture that accumulates at night may collect on the trees and fall as dew, replenishing some soil moisture. Reforestation campaigns in deserts are questionable efforts, without artificial watering or human maintenance they usually die. However active afforestation campaigns in semi-deserts bear some merit. However, there's no evidence of artificially planted forest sustaining itself in such an arid environment without human intervention.
Another example are drought tolerant trees, like acacias, planted in the Sahara. These may very well sustain themselves with their ability to settle and accumulate more water.

They provide shade and so prevent the surface soil from overheating, which has several benefits

With cooler soil, the little soil moisture that falls here can percolate into the ground without evaporating
It shades wildlife from extreme heat (who in turn produce fertilzer i.e. manure/urine)
The areas under trees become attractive nesting sites for birds who nest in winter

For more examples of greened ecosystems, there's the Hawaiian island of Ni'ihau. This is privately owned and very arid because of the rainshadow effect. The owners planted tens of thousands of trees a year for decades. As a result, the trees act as a humidifier to collect what little atmospheric moisture accumulates at night when it's cooler.
Another example is Ascension Island. In the 1850s, botanists (under encouragement by Charles Darwin) started shipping trees to the island. In mere decades, the peak of the island became a cloud forest.
I don't know if such examples are self sustaining. I can only say it's "Plausible". Ascension Island is not well developed, therefore little maintenance is done on the forest above, and it's a national park.
In more arid regions, it's possible but don't expect a full blown forest. You might see a semi-arid scrub forest.


Can ocean temperatures affect groundwater storage capacity ?

I think the abstract of the article addresses your question. Working backwards, it presents two direct causes of change in groundwater storage. The first is climatic - greater precipitation tends to increase storage and a decline in precipitation will reduce recharge and thus reduce storage. The second is the anthropogenic response to changes in climate (they focus on changes in precipitation but there may be a second effect of changes in air temperature). When there is less rain, more water will be pumped for irrigated agriculture.

These two effects are then related to the way the change in precipitation is affected by change in ocean temperature. So changing ocean temperature changes the rainfall amounts and patterns. The rainfall reduction in northwestern India increases the amount of groundwater pumping needed for agriculture and decreases groundwater storage.

Methods have been developed to separate the climate and pumping effects on waterlevels (Shapoori, V., et al. 2015).


The impedance inversion problem asks: "Recover acoustic impedance from seismic reflection waveforms". The forward modeling procedure from acoustic impedance to seismic reflection waveforms involves calculating reflection coefficients and then convolving these with a wavelet.

Let's assume, for now, that you have perfect seismic resolution and therefore your wavelet is of infinite bandwidth. This means that the inversion problem becomes: "Recover the acoustic impedance from a given set of reflection coefficients".

As shown by Peterson et al. (1955), for small contrasts in acoustic impedance, the reflection coefficient equation can be linearized as shown below. Linear problems are much much easier to solve computationally than non-linear. This makes the forward model calculation a simple difference, the discrete analog to a derivative. Note: this is for normal incidence but a similar analysis can be done for non-normal incidence.

So... if it takes a derivative to calculate the reflection coefficient, it must take an integral to calculate the acoustic impedance. However, as everyone knows, when you integrate any function, you inevitably run into the non-uniqueness caused by that dreaded +C at the end of all integrals.

That +C, in this context, means that there are an infinite number of acoustic impedance models that can give you the exact same reflection coefficients. So you need the +C (i.e. the DC, or zero frequency, or additive constant) information to do a complete inversion and really recover the true values of impedance in the earth. All you get from the seismic are the reflection coefficients (and that's with infinite resolution), so you will need to get this DC information from another independent source.

In practice, the inversion is not done by a simple integration but by setting up a linear system and iteratively converging (by something like conjugate gradient) to the answer that minimizes some misfit function between the forward model and the data. As complex as that sounds, deep down, we are pretty much just doing a careful integration.

Hope that helped.

Peterson, R. A., W. R. Fillippone, and F. B. Coker, 1955, The synthesis of
seismograms from well log data: Geophysics, 20 (3), 516–538.


What is the long term impact of large scale removal of material from subterraneal caches on the structural integrity of the soil?

The answer to your question will depend on the type of material and the depth. I will restrict this answer to groundwater withdrawal to focus the discussion.  Of course there can be effects from other extractive industries.

Groundwater pumping can lead to large scale subsidence, with the Central Valley of California being one of the best described examples. According to that website, "More than 80 percent of the identified subsidence in the United States is a consequence of human impact on subsurface water."

Overall, the extreme subsidence shown may cause damage to foundations, etc. but is spread over a large area and is pretty even, unlike your classic sink-hole.  It is the differential settling that causes the most damage.

There are several types of sink holes (also called dolines), they may be related to failure of indurated rock above cavities or by failure of soft soils/sediments. The most common natural sinks occur through the dissolution of limestone in 'karst' terrain and they can be kilometers across. This can lead to the creation of water or air filled caves. In some cases a cavity forms in sediments above the limestone and can subsequently collapse. Cavities can also be formed in sediments where they are removed through pipe erosion but that tends to be a shallow phenomenon (but can still be damaging).

The description, above, talks about natural processes but these can be enhanced by groundwater pumping.  The water supports some of the overburden and removing it weakens the structure and can lead to collapse. Flow systems can change, enhancing subsurface soil erosion as water tables decline. And of course, building over a cavity may exceed the load bearing capacity.

So the long term impacts will depend on both the geologic setting and the severity of water level decline. Will this have a major effect on global infrastructure and economies? I suspect not but the damage we have seen in certain areas is likely to continue and perhaps spread.

A somewhat old but good reference on the subject sinkholes and caves that discusses the land-use issues is Geomorphology and Hydrology of Karst Terrains. White, William B. (1988). Oxford University Press.


What is it called when water forms to look like a root structure?

The term you are looking for is Dendritic, it literally means "having a branched form resembling a tree" and is used to describe the shape of rivers but can also apply to anything with that pattern.


Direct measurments of vertical ocean mixing?

I am assuming you know how to get to mixing from velocity field since you are talking about the noise in the ADCP data. The way people get the small fluctuation and vertical mixing profiles that are highly trusted are with "micro-structure" sampling technique.

Please follow this link for more detail on that technique.
https://earthobservatory.nasa.gov/blogs/fromthefield/2012/10/04/what-is-ocean-microstructure-and-why-study-it/


Definition of Surface-based atmospheric duct

Both situations are possible. Normally, the atmosphere gets colder and more rarefied with height, and cold air holds less moisture than warm air. Inversion layers trap the lower air mass closer to the ground, so there is a reversal of what you might normally expect: temperature and humidity rises as you get higher, rather than the normal decrease. Inversion can occur in several ways, for example, if a mass of warm air moves in over a cold surface, an inversion will take place. Bothe statements you quote are correct, but the second one is more usual.


Why do the earth sciences use mega-annum instead of mega-year?

Both mega-annum(Ma) and mega-year(Myr) designate one million years.  The distinction is that Ma is used to designate the time before present or geohistoric dates and Myr to designate a duration or span of time.  So if you want to say a rock is dated to 10 million years before the present you would use 10 Ma, and if you want to say that a rock is 10 million years old you would use 10 Myr.

There has been debate among scientific disciplines to simply adopt Ma as the standard unit.  However, the distinction that geologists have been using to distinguish between dates and durations for decades can best be illustrated as such:

  No one objects to the storming of the Bastille on 14 July 1789 (a
  date) or to the construction of Stonehenge from 2600–1600 BC (an
  interval specified by two dates). In the case of the latter, we say
  that the job took 1000 years, not 1000 BC. The distinction between
  geohistorical dates and spans of geological time is conceptually
  analogous. There is no internal inconsistency, and the International
  System of Units (SI) rules don’t apply to dates in either case because
  points in time are not units, even if they are specified in years
  (Aubry et al., 2009). The year, moreover, is not a part of the SI. It
  cannot be a “derived unit of time,” the designation proposed by the
  task group, because under SI conventions “derived units are products
  of powers of base units” (BIPM, 2006). The base unit for time is the
  second. The task group is thus intent on fixing a problem that doesn’t
  exist and in a manner that is at odds with their stated goal of
  “adherence to SI rules.”

The above quote is from the Geological Time Conventions and Symbols manuscript from 2011.  More detailed discussion can be found at this source.  This Science Blogs article from 2009 has some interesting discussions regarding this issue.


How are the Scala dei Turchi staircases formed?

There's no need to invoke stretching here. This is just a simple case of dipping sedimentary beds which have been eroded by the sea.

The stepped geometry may be caused by small variations in the hardness of the beds such that the harder beds weather out more prominently and create the steps.

Alternatively, at least some of the larger steps may be wave cut terraces formed during periods of stable sea level. In the background on the left of the picture you can see two large terraces separated by a ramp which look very much like wave cut terraces. Such terraces are well known from central Greece, where they have been uplifted by activity on faults and I would speculate that a similar process has occurred here.


How much does COVID-19 affect weather forecasts?

Welcome to Earth Science SE!

Given that the crisis is still ongoing, I doubt we know the full extent of the impact (forecasting the weather is hard enough, forecasting the impact of a pandemic is outside my expertise). But, at least one conference  was supposed t
o go to was cancelled. And I know the lack of airplane obs is impacting data assimilation. Beyond that, I am not sure. Some hypotheses perhaps include:

Is the change in the quality of life may be impacting forecaster accuracy?
What impact does the delay in communication of scientific research have on forecast accuracy?
How does this impact the future science budget?
How does the absence of airplane data degrade forecasts (could be evaluated using a OSSE experiment)? On a related note, how
How is the communication of weather forecasts by in-studio meteorologists compare to meteorologists that are in self-quarantine?

How this ordeal has affected weather forecasts may be a good cross-disciplinary study for the future.

To fully answer your question, you can look at Benjamin et al. (2006) to evaluate the relative impacts of different observational systems. Certainly there have been some changes since then, but this can give a cursory idea of what we might be looking at.


Evergreen trees grow faster than most hardwood deciduous trees, so their absorption and oxygen emission is greater.
Note that trees do not "clean" air. Plants emit oxygen which is why air in a house with lots of plants will seem more fresh. In the global environment algae and other primitive organics are primarily responsible for converting CO2 to oxygen, not trees.
Particulate pollutants and some compounds with good water solubility, like sulfur dioxide and ammonia, are removed from air by moisture which condenses and falls to earth bringing the particulates with it.


can wet winters require more home heating than colder winters, in same place?

This probably has less to do with the rain and more to do with the wind. The wind helps move the colder air that is outside into your house more easily because there is more force being exerted on your exterior walls and therefore cooler air can work its way through any small cracks. Sorta similar to the wind chill being colder on windier days. The lessened amount of sun also comes into play as even in the dead of winter it helps warm surfaces, even just a tiny amount.

Welcome to the Earth Science exchange!


Are there gases from the Earth useful to generate electricity besides "natural gas"?

The category "other gases" may not solely include other naturally occurring gases extracted from the Earth.

As you state natural gas is predominantly methane, extracted from the Earth.

Another type of gas commonly used is petroleum gas, which is prepared by refining petroleum of wet natural gas. Petroleum gas is propane or butane.

Coal gas, which was manufactured from coal and largely consists of hydrogen, carbon monoxide and methane, is no longer manufactured or used.

Another type of gas that could be included in the category is biogas, which is a manufactured gas made from biological waste products, such as: manure, sewage, food waste and green waste. Biogas is predominantly methane.


Why is the core of the earth thought to be iron rather than metallic oxygen?

1) The density of the core approximately matches that of high pressure Ni-Fe, but is way denser than solid oxygen (roughly 1.4).

2) If the core was oxygen then the overall elemental abundance of the Earth would be nothing like the elemental abundance of anything else in the Solar System (or anywhere else in the known universe).

3) The elemental abundance in meteorites, thought to be left-overs of the original accretionary disk, closely matches Earth with an Fe core - doesn't resemble in any way any supposed metallic oxygen core.

4) The seismic data works well if we assume a liquid / solid iron core. If the core was solid oxygen, then the P-wave shadow would be configured completely differently, because seismic refraction at the core-mantle boundary would bend to make shallower refracted waves, not deeper.

5) A metallic oxygen core would could not explain the Earth's magnetism.

6) It would be bizarre for an oxygen core to have evolved when there are much heavier elements in the mantle.


Part of the current topography might be due to a hot upper mantle below the Rocky mountains. This can be determined by seismic tomography. The hot mantle creates isostatic uplift.

Just one of many pictures I found:

http://srl.geoscienceworld.org/content/83/1/23/F2.large.jpg


You will probably never know for sure, but the only way to get any confidence is to have any potential specimens analyzed by a mineralogical laboratory that can do Gamma spectroscopy.
Fake trinitite,

use a variety of means to achieve the glassy green silica look as well as mild radioactivity; however, only trinitite from a nuclear explosion will contain certain neutron activation products that are not found in naturally radioactive ores and minerals. Gamma spectroscopy can narrow down the potential nuclear explosions from which the material formed.

Also,

If it's too green, too translucent or too inexpensive to be true, it probably isn't real Trinitite!  So how does the collector know if a specimen is authentic?  Well, usually the only means for the collector to eliminate the fake stuff is to use a sensitive dosimeter and take a reading to verify that residual induced radiation exists.  This will be very small, but it can be detected.  This will not rule out the possibility that clever fakers will not add some small amount of weakly radioactive material to their formula.  The only way to be 100% certain of authenticity is by means of nuclear energy spectroscopy.

One of the radioactive elements to test for is Cesium 137,

This radionuclide has a half life of 30.2 years and is one of several unique byproducts of nuclear fission or atomic detonations.  It is present in all authentic Trinitite specimens.

All radioactive elements have a half life. The radioactive elements produced by the Trinity Test on 16 July 1945 are also well know. To increase the confidence of testing, the amount of each radionuclide in each sample would need to be detected and compared with the expected amount that would be in true Trinitite given the elapsed time since 16 July 1945.
If the specimens have a report from testing laboratory, get a copy of the report and verify it with the laboratory. Ideally, such reports should had a picture of the sample that was tested. If so, ensure it matches what is being offered for sale.


What is difference between divergent boundary and hot spot?

Divergent boundaries occur at the boundary between plates. A divergent boundary is where two tectonic plates are actively being pushed apart. Divergent boundaries create rift valleys on land and eventually ridges on ocean floors, where hotter material wells up from the mantle, cools and form new crust. For example, the East African Rift Valley (a divergent boundary), is pushing apart the African plate, separating Somalia from the continent. Eventually the rift valley will flood, producing a ocean between the newly split plates with the East African Rift becoming a mid-ocean ridge.

Hot-spots, or mid-plate tectonic activity, occur away from boundaries between plates. A hot-spot is where a plate is moving over a stationary mantle plume. Hot-spots are responsible for island-chains, such as those seen in Hawaii, which form as the plate slides over the plume or even volcanoes on land, like Yellowstone. The islands of Hawaii lie thousands of kilometres away from the boundaries of the Pacific plate on which they sit. A nice feature is that the Hawaiian island chain lies in a north-westerly line that matches the direction the Pacific plate is moving.

The main thing to keep in mind is that divergent boundaries occur at the boundaries of plates. Hot-spots occur in the middle of plates, often thousands of kilometres away from the boundaries of the plates.


Would the atmosphere move rigidly with ground if you ignored wind?

I think you’re mixing up frames of reference a bit here.  That ~400 m/s speed of the surface is relative to an absolute, non-rotating frame of reference in which an observer sees the Earth as spinning on its axis.  In meteorology we typically use a rotating frame of reference that spins with the Earth, in which an observer sees the surface as moving at 0 m/s.  When we talk about wind, we talk about air motion relative to this rotating frame.  You essentially say this in different words:

… since both speeds need to be relative to the same reference (the ground)...

So, if all winds disappear (i.e., wind speed = 0 m/s) then all the air is moving with the rotating frame by definition.  There’s no meteorology or fluid dynamics invoked here, this just falls out from our chosen coordinate system and definition of “wind”, so it would be the same at 2 m or 25 km altitude.
NB Your definition of air speed changes from "minus" in the first para to "plus" in the last para; I've assumed that this was a typo.


Why are there no snakes in New Zealand when ecosystem needs them

Snakes are important in some ecosystems because they keep down vermin, but the natives of these places pay a high price for this service. Why does new Zealand not have any? Maybe like Ireland there was a water barrier preventing snakes from reaching the islands. Australia is swarming with snakes, most of them very poisonous, but maybe it wasn't when New Zealand broke free many millions of years ago.

Another possibility is that there were once a few snakes in New Zealand, but predators like the Giant Moa and its relatives, and snake-eating birds of prey, might have hunted them to extinction. As for Ireland, snakes were killed off or driven out by the Ice Age, and when the ice receded the snakes from Europe were too slow to get there before the Irish Sea was formed. Only three species manged to reach England before it was cut off by the Channel. Snakes are not important for British ecosystems, but not many people would like to see them become extinct here. Only one, the adder, is poisonous, and kills about one person every fifty years. Just as British ecosystems could survive quite happily without snakes, so can New Zealand. To introduce even harmless ones there could risk a similar eco-disaster to the one in Australia caused by the introduction of the cane toad.


You probably mean 50kgN/ha, which sounds like a plausible number for fertilizer application.

I don't know what you are doing exactly, but you need to know how much surface area your soil sample represents. If you do planting tests, it will be simply the surface of your bed.

Then it's just mulitplying the surface area by 50kgN/ha (mind the units!). Now you know how much N you need.

If you buy fertilizer, the fertilizer value in kg/t, kg/m³ or some similar measure will be given for the important macronutrients NPK. Else you need to know how much N is in Ammonia per weight but I think that is the easy part.

Disclaimer: I've never done any soil science, but I worked with farmers for a while and was in a field where fertilizer etc. matters.


How much of Earth's land area has antipodal land area?

A rough idea, using the Lambert Conformal image at the Cartopy projection list and Gimp:

The gold area should be the overlap.  So basically parts of South America with Indonesia and SE Asia... and Antarctica with the far northern islands of the northern hemisphere, plus a few smaller areas from islands like New Zealand and Hawaii and even smaller.

That assumes I did properly invert it.  To do so, I just vertically flipped the image, and offset it by 180 degrees.  Thinking that should be all that is needed.

So in the end it looks like it's not a lot of area at all.  Further exact statistics would take some GIS work (probably quicker than GIMP in the end!)  A central starting guess would be 8.5% (the 29% land cover squared), but particulars will make it a bit higher or lower.


These days I use: ncgeodataset. The routine allows for the extraction of a subset of data without having to load the entire file or even an array into Matlab. It is great for large datasets.


How has river to ocean flux changed over the last 500 million years?

There is no direct answer. One way to think about this is to consider the water cycle. Water evaporates from the oceans and is precipitates over land. Distance from the ocean affects the amount of precipitation so at the center of a large contintent you may have less precipitation than over a smaller one. Mountains also drain moisture out of the air as it is heaved. hence the topography of the continents affect this effect. A Pangea directly after collisions will likely have more and higher mountains than a later stage when break-up is imminent. Location on the earth's surface is a third factor since we have larger scale circulation belts that affect the atmospheric conditions so that we have a tropical belt (the Intertropical Convergence Zone) around the equator, a drier zone north and south of the ITCZ, followed by temperate and polar zones towards the poles. Hence the location of the continent(s) and their topography will affect the zones and the zones will will determine which parts receive more or less precipitation. Furthermore the movement of the continent(s) through these climate zones change conditions as well.

In summary, we can be sure it is not constant over geological times. The only possible way to get some relative handle on the question would be to try to apply a global circulation model to past continent configurations, including topographical effects and see what comes out, being aware of all uncertainties and comparing with geological evidence.


How does friction and radiolysis provide hydrogen for "unusual types of methane"?

I found this paper 1 trying to understand what is radiolysis. The decomposition of water by ionization happens at basaltic aquifers on the seafloor, close to seabed.

  "Water radiolysis is the decomposition of water molecules by ionizing
  radiation produced during the decay of radioactive elements (Debierne,
  1914; Le Caër, 2011). The principal radioactive elements that produce
  ionizing radiation in basalt are uranium (238U and 235U), thorium
  (232Th), and potassium (40K), which collectively emit alpha (α), beta
  (β), and gamma (γ) radiation as they and their daughter nuclides
  decay. Transfer of energy from this radiation excites and ionizes
  water molecules, producing several chemical species: eaq-, HO•, H•,
  HO2•, H3O+, OH-, H2O2, and H2 (Spinks and Woods, 1990; Le Caër, 2011)."

  "The oceanic basement contains the largest aquifer on Earth. Its
  fractured rock contains nearly 2% of Earth’s total volume of seawater
  (Johnson and Pruis, 2003). Although the extent of life and microbial
  activity in oceanic basement is not well known, a variety of evidence
  suggests that microbes reside within the aquifer (Cowen et al., 2003;
  Edwards et al., 2012; Jungbluth et al., 2013; Lever et al., 2013;
  Orcutt et al., 2013). Fisk et al. (1998) and Staudigel et al. (2008)
  report weathering textures suggestive of microbial alteration in
  subseafloor basaltic glass."

  For subseafloor environments, we are particularly interested in the
  production of the reductant H2. Many organisms catabolically utilize
  H2, including methanogens, sulfate-reducers, iron reducers, and
  nitrate reducers (Fang and Zhang, 2011). There is evidence that some
  of these organisms, specifically sulfate reducers and methanogens, are
  active in subseafloor basalt (Lever et al., 2013). Radiolysis
  undoubtedly occurs in subseafloor basalt, as both water and radiation
  are present. Edwards et al. (2012) suggested that in the old and
  relatively weathered basaltic basement of the South Pacific Gyre
  (SPG), radiolytic H2 may be the dominant electron donor.

Trying to understand how hydrogen can be formed by friction I found this other one 2 where the author asociates it to earthquakes, listing three possible origins for hydrogen and saying the frictional origin is still a not well known process. Apparently it happens at fault systems when there are mouvements on lithosphere:

  In the last few decades, three different abiotic H2 generation
  processes have been proposed:

  (1) water–rock redox reactions, mostly under hydrothermal conditions    [Janecky and Seyfried, 1986; Coveney et al., 1987],
  (2) radiolytic reactions of H2O [Savary and Pagel, 1997], and
  (3) mechanoradical formation on wet fault surfaces during earthquakes    [Wakita et al., 1980].

  H2 production by peridotite‐
  water and komatiite‐water hydrothermal reactions, as modern and
  ancient analogs, respectively, has been quantitatively estimated in
  laboratory experiments [Seyfried et al., 2007; Yoshizaki et al.,
  2009]. Radiogenic production of H2 is supported by the analysis of
  H2‐bearing fluid inclusions in quartz containing U‐bearing minerals
  [Dubessy et al., 1988], and has been quantitatively estimated in a
  laboratory g‐irradiation experiment [Lin et al., 2005]. The H2 flux
  per unit of surface area from redox reactions has been estimated to be
  3 × 10−4 mol/m2 yr from a 1 km column of mafic/ultramafic rock with 10
  wt% FeO [Sleep and Zoback, 2007], and the estimated flux from water
  radiolysis in the Witwatersrand basin, South Africa, is 8 × 10−6
  mol/m2 yr [Lin et al., 2005]. In contrast, the H2 flux associated with
  earthquakes and its significance in subsurface ecosystems has not yet
  been explored in either the field or laboratory.

After making experimental flux calcs the paper says this mechanism may have been important for methanogens. And not only eartquakes but meteorite impacts too may have been a source of mollecular hydrogen for primigenious  life not only on Earth but on other planets.

  "Thus, seismic activity and the consequent release of H2 might have
  sustained subsurface microbial communities as long ago as 3.8 Ga.
  Moreover, mechanoradical H2 generation can be induced by meteorite
  impacts as well as by earthquakes, and thus might play an important
  role in the evolution of subsurface biosphere not only on Earth but
  also on other planets."

1 Dzaugis Mary E., Spivack Arthur J., Dunlea Ann G., Murray Richard W., D’Hondt Steven (2016). "Radiolytic Hydrogen Production in the Subseafloor Basaltic Aquifer" Frontiers in Microbiology, 7, ISSN=1664-302X

2 T Hirose, S Kawagucci, K Suzuki (2011) "Mechanoradical H2 generation during simulated faulting:
Implications for an earthquake‐driven subsurface biosphere." Geophysical research letters.


What is the concentration of silver in tap or freshwater in the United kingdom

Monitoring results from UK groundwaters 1996-2007, Silver:

Sites 2929

Samples 19420

Min <0.04 µg/l

Max 79.6 µg/l

Average 0.457 µg/l

Source - Defra

  Routine monitoring for trace elements in drinking water is only
  conducted for the elements specified in the Water Supply (Water
  Quality) Regulations. Specified elements include antimony, arsenic,
  boron, cadmium, chloride, chromium, copper, fluoride, iron, lead,
  manganese, mercury, nickel, selenium and sodium. Monitoring for other
  elements will only normally be conducted in response to specific
  identified risk. Recently DWI has funded investigations of uranium1
  and molybdenum2 in drinking water in response to recent developments
  in WHO guideline values. Both these studies showed a good level of
  compliance should the WHO guideline value be adopted as a standard.

Also...

  Water companies also conduct raw water monitoring and these results
  are reported to Drinking Water Inspectorate. Preliminary analysis suggests most of the
  raw water monitoring relates to elements already covered by the
  regulations but a few companies monitor for additional elements in raw
  water. A summary of the additional elements and (number of companies
  monitoring). Silver (4).

Source - Defra 2

  Average silver concentrations in natural waters are 0.2-0.3 µg/litre.
  Silver levels in drinking-water in the USA that had not been treated
  with silver for disinfection purposes varied between "non-detectable"
  and 5 µg/litre. In a survey of Canadian tapwater, only 0.1% of the
  samples contained more than 1-5 µg of silver per litre. Water treated
  with silver may have levels of 50 µg/litre or higher; most of the
  silver will be present as nondissociated silver chloride.

Source - WHO


The sun sometimes appears pure white after rainfall, how can this be explained?

When it rains the raindrops nucleate around aerosol particles of salt, dust, clay, soot, dimethyl sulphide, etc. In addition a falling raindrop may pick up any particulate matter that may be in its trajectory. The net result is that rain 'scrubs' the atmosphere clean. Without all these polluting particles to diffuse different wavelengths of the spectrum, the eye perceives the 'full spectrum', which the brain interprets as 'white light'.

In addition, you are quite correct that the eye's response to light, and to what constitutes 'white light' is very variable, depending upon light intensity, extent of blue sky vs. cloud, direction relative to the sun, reflections from buildings, the sea, etc. and other factors.


Is "seismic energy released" a regionalized variable and can be analyzed using geostatistics?

An intrinsic assumption in using geostatistics is that one can approximate a distribution by a polynomial surface. In practice, maybe you can do this in a very simple geological situation, such as an isotropic shockwave arising from sedimentary compaction in horizontal sediments. When it comes to major seismic events at tectonic plate edges I think the seismic energy distribution might be too complex. For example, the seismic energy is attenuated at different rates on either side of a subduction zone, and tends to be channeled along the ocean floor according to local bathymetry and structure (especially along mid-ocean ridges). Also, the shock wave distribution will be different according to whether the source is shallow or deep. Trying to account for such features in a geostatistical model will be a nightmare of complexity - good luck!


How on "Earth" can you make all those measurements of Earth forming?

How on “Earth” can you make all those measurements of Earth forming?

One word: Zircons.
Zircons rank very high amongst the techniques used to measure the age of the Earth, and the age at which the Earth later cooled down. One of the key elements in zircons is zirconium. There are other elements that have similar chemical characteristics to zirconium. One of these is uranium. Both uranium 235 and uranium 238 eventually decay to lead. Lead is extremely incompatible with zirconium from a chemical perspective. All of the lead in a zircon could only have resulted from radioactive decay.
The question focuses on the "boring billion" years in the Earth's history that occurred well after the Earth formed (over three billion years after the Earth formed). Zircons were key in that analysis as well. There are other elements other than uranium that are chemically compatible with zirconium. One of these is europium. The presence or absence of europium in zircons indicates whether or not mountains were eroding at the time those zircons formed. The ratio of uranium to lead in those zircons indicates how old those zircons are.


Is there any information on the height of waves near New Zealand resulting from today's M 8.1 Kermadec Islands earthquake?

Norfolk Island experienced a tsunami wave 64 cm tall. In Australia the tsunami wave was 10 cm at Tweed Heads and 9 cm at Port Kembla. In Vanuatu the height was 32 cm and in Fiji 13 cm  and 8 cm in Tonga.
Australian Burea of Meteorology report
TSUNAMI DETAILS:
The following sea level gauges have observed a tsunami, heights refer to wave
amplitudes (positive wave values):
Name                  Country       Lat     Lon      Height (m)  Time (UTC)
East Cape             NEW ZEALAND   37.50S  178.17E  0.15        04 MAR 2210
Nuku'Alofa            TONGA         21.10S  175.20W  0.06        04 MAR 2115
Suva Viti Levu        FIJI          18.10S  178.42E  0.13        04 MAR 2200
Rarotonga Wharf       COOK ISLAND   21.20S  159.79W  0.08        04 MAR 2200
Kaingaroa Chatham Is  PACIFIC OCEA  43.70S  176.27W  0.22        04 MAR 2320
Norfolk Island.       AUSTRALIA     29.10S  167.95E  0.64        04 MAR 2245
Port Villa            VANUATU       17.80S  168.31E  0.32        04 MAR 2320
Ouinne                NEW CALEDONI  22.00S  166.83E  0.2         04 MAR 2320
Tubuai                FRENCH POLYN  23.30S  149.48W  0.06        04 MAR 2305
Port Kembla           AUSTRALIA     34.50S  151.00E  0.15        05 MAR 0205
Mare                  NEW CALEDONI                   0.15        04 MAR 2330
North Cape            NEW ZEALAND                    0.15        04 MAR 2130
Great Barrier Island  NEW ZEALAND                    0.20        04 MAR 2240

See also [1], [2] & [3]


Where does the lithium in Salar de Uyuni comes from?

Due to its increasing economic importance, Lithium deposits are coming under more intense scrutiny, by organisations such as the United States Geological Survey (1).  The Salar de Uyuni deposit in Bolivia is one of the deposits of lithium brine that is undergoing modelling and research.

The USGS noted that all lithium brine deposits have some very similar characteristics, climatically, they are in arid environments, be near one or more aquifers and have had sufficient time for the accumulation of the lithium from weathering processes, other commonalities include the tectonic settings, associated volcanic/hydrothermal activity and local petrology (lithium bearing rocks) (1).

The geological setting of the Salar de Uyuni is described by the USGS (1) as being situated in the Altiplano of Bolivia and Chile - a high, internally drained plateau along the crest of the Andean convergent boundary orogen, that includes closed basins. Active faulting is present, causing in subsidence, allowing sediments to accumulate.

Observations made by Hofstra et al. (2013) (2) in similar lithium brine deposits in the United States came to the conclusion that melt inclusions in quartz phenocrysts in rhyolite tuffs in association with hydrothermal deposits of tin, molybdenum and beryllium have been found to be heavily enriched in lithium (to the order of 1000's ppm).  Hofstra et al. (2013) surmise from these observations that the source of the lithium has been leached out over time from the nearby rhyolitic tuffs of the Bolivian tin belts to the east of the Salar de Uyuni (2),(3).

The lithium is then leached out of the rhyolite by meteoric water, draining into the basins and concentrated by evaporation in the local arid environments.

References

(1) Bradley et al. 2013, A Preliminary Deposit Model for Lithium Brines, USGS Open-File Report 2013–1006

(2) Hofstra et al. 2013, Silicate Melt Inclusion Evidence for Extreme Pre-eruptive Enrichment and Post-eruptive Depletion of Lithium in Silicic Volcanic Rocks of the Western United States: Implications for the Origin of Lithium-Rich Brines*, Economic Geology

(3) Arce-Burgoa and Goldfarb, 2009, Metallogeny of Bolivia, Metalliferous Ore Deposits of Bolivia


How long ago was the first limestone formed?

Probably at the Hadean or at the beginning of the Archean, but there is no geological registry.

The mechanism that can lead to inorganic limestone formation is weathering of magmatic carbonatite rocks. I found Siilinjärvi carbonatite complex in Fennoscandia is dated 2.6Ga (Tichomirowa et al, 2013), so Archean. It is the oldest one I found.

Another mechanism that could produce limestones in ancient eons is described by user @BillDOe in this related answer:

  Once life evolved in the world's oceans, the vast majority of
  limestone formation has been through the organic process. However,
  before life did evolve, limestone formed through an inorganic process
  where rain water falling through a CO2-rich atmosphere reacted to form
  a weak carbonic acid solution that then reacted with
  calcium-containing minerals to form calcites. This then washed into
  the world's oceans to form limestone deposits.

The premise comes from this stanford.edu work and is a bit controversial because there are no proofs limestones formed by this mechanism.

International Stratigraphic Chart image

M. Tichomirowa, M.J. Whitehouse, A. Gerdes, J. Götze, B. Schulz, B.V. Belyatsky (2013): "Different zircon recrystallization types in carbonatites caused by magma mixing: Evidence from U–Pb dating, trace element and isotope composition (Hf and O) of zircons from two Precambrian carbonatites from Fennoscandia", Chemical Geology, Volume 353, Pages 173-198, ISSN 0009-2541.
https://doi.org/10.1016/j.chemgeo.2012.11.004.


Could the speed in which the plate is moving affect how quickly mountains rise?

The height of the Himalayas

Like Keith McClary says in his answer, there really are two factors in creating growing/shrinking mountains.

Mountains grow due to various reasons. In the case of the Himalayas it's like you must've seen in the documentary: the collision between the Indian and Eurasian continental plates. The material has to go somewhere and thus goes up (simplifying the geology a bit; I think that concepts like buoyancy these days also give some nuance to the subject, but the general picture stays the same). In the Himalayas, the two plates have moved into each other for at least 2500 km, so that's a lot of ground to move!

If that was the only process at play, there would be way higher mountains. I couldn't find a corresponding figure for the Himalayas, so consider instead the following present-day profile through Switzerland, running roughly north (left) to south (right).

You can see that the present-day Alps are at maximum 4 km high. Compare that against a reconstruction of the geology that should be present, running along basically the same profile:

You can see that the mountains could be as much as 20 km high! You can appreciate just how much mountain has disappeared, for another very young mountain range! So, the reason that mountains aren't as big as they could/should have been, is that they are cut down by erosion. Rain, snow, wind, temperature, all break down mountainous rocks into smaller broken pieces. Those pieces are transported away from the mountains as sediment in rivers (such as the Yangtze for the Himalayas).

So, the height of the Himalayas is very much controlled by the relative size of the two effects: how fast does the mountain range grow, and how fast does erosion break it down again. If the two are in equilibrium, the mountain doesn't shrink or grow. If erosion dominates, the mountain will slowly disappear over time. But in the case of the Himalayas, the mountain building generally outpaced the erosion, leading to the unique heights of the Himalayas. In this case, the speed of the collision is definitely the main factor!

The size of the Tibetan Plateau

Now if your question was also about why the Tibetan Plateau is so wide (rather than the Himalayas so high), I recommend you read https://oak.ucc.nau.edu/wittke/Tibet/Plateau.html , a very well-written summary of the three main hypotheses:

The speed of the collision has lead to a very step-wise straight faults toppling over each other, rather than folding over, which could lead to very long faulted sections. "Crust is thickened by the faulting and subsequent movement of large masses of rock, which are stacked one on top of another like cordwood."
When India hit the Eurasian plate it still had a heavy oceanic plate that was going under ('subducting') under the Eurasian plate. Now the oceanic plate has disappeared, and now the continental plate is being pulled underneath the Eurasian plate. "This process is reminiscent of taking a block of ice and pushing it beneath another ice slab, causing the latter to rise upwards. However, it is difficult to imagine how the buoyant Indian crust could be kept deep enough to get far beneath the plateau before bobbing to the surface. Perhaps the great speed at which India is colliding to Eurasia allowed this to happen."
The last hypothesis is simply that the continental collision puts a lot of heat below the plateau. "Like a hot-air balloon, the heated crust is buoyant and rises with the addition of light granitic material at the bottom of the Eurasian crust increasing the height of the Plateau."

This picture shows all those three hypotheses. 1=distributed shortening, 2=underthrusting, 3=lower crustal flow. In each case, a plateau is formed relatively far away from the actual collision between the two plates.

It is likely that, really, all three hypotheses together are at play. As explained on the website, at least the first two hypotheses are thought to be related to the speed of the collision.

So, yes, both the height and the width of the Himalayas are thought to be linked to the speed of the collision/relative plate movement!


Do Siberia and Canada have a rasputitsa?

In Canada there is definitely a rasputitsa period, though it does not occur everywhere or necessarily in the fall, and it is not considered a rasputitsa by name.  Every spring in most parts of Canada there is a period of time when many of the soils are saturated with water from the recent snow melt.  The various forest services and companies will often close roads or reduce the load limit during the spring thaw specifically because the roadbeds are saturated to the point that large equipment can punch out the roads and if bad enough get stuck.  Even the major highways in parts of the western prairies and in many mountainous areas have reduced load limits just after spring melt because of issues with the roadbed being saturated.  This issue mainly affects the tertiary road systems because modern road construction methods are developed to reduce the effect of the spring thaw on the stability of the roads.  The post here describes the highway load reductions.


What exactly are enantiotropic and monotropic polymorphic transitions?

If you can get your hands on a copy of Fegley's book Practical Chemical Thermodynamics for Geoscientists, he gives a good description in Chapter 07, which I'll summarize here.

An enantiotrope is a polymorph that undergoes a reversible transformation into another polymorph at atmospheric pressure. If you're not familiar with the concept of reversibility you may want to read up on entropy, spontaneity, and the 2nd law of thermodynamics. Briefly, a reversible transformation is a process in which the system and surroundings are in equilibrium at all times. An important property of these processes is that $\Delta$ S$_{universe}$=0. Reversible processes don't actually occur in nature but they can make good approximations for some things we observe.

A monotrope is a polymorph that does not have a reversible transformation into another polymorph at atmospheric pressure. One polymorph is always stable and the other is metastable. Monotropy exists in systems where the transition temperature between solid polymorphs is above the melting point of the lower-temperature polymorph. In many cases, upon heating the metastable monotrope melts, then resolidifies to the stable monotrope, which melts at a higher temperature.

Metastability refers to a nonequilibrium state that is approaching equilibrium slowly enough that we can say it's stable over a given period of time.


Database of geological group or formation exposures?

You may also find localised geological guides, such as the Roadside Geology series.

http://geology.com/store/roadside-geology.shtml has a listing. While I have not used them, I have seen them crop up fairly often as a nice option when looking for interesting geology in more general terms, including for some outcrops.

(I would have made this a comment, rather than an answer, but have no rep yet.)


Why is the Yarkant River braided in the Pamir mountains?

Braiding will occur in any river where two conditions are met: 1) a very high sediment load must be available, as is usually the case in a peri-glacial or post-glacial environment, and 2) there is an abrupt change from high energy rivers (steep hydraulic gradient) to low energy deposition with flat space on either side of the river. Go for a hike in any glacial or post-glacial mountains and you will see that rock hardness has little to do with sediment availability - there is always more sediment than the river can mobilize at any one time, even in extreme floods. The classic example is the Canterbury Plains on the east side of South Island New Zealand. Braiding is an inherently unstable and transient river configuration.
Meandering is the river's minimum energy configuration. It is another chaotic process, achieved through helicoidal flow and superelevation on the convex side of a bend. It will occur anywhere the river is laterally unconstrained, and where the rotational kinetic energy, perpendicular to the direction of flow, is a significant fraction of the forward kinetic energy.


How large can local surface CO2 concentration vary due to natural processes?

There are many studies quantifying temporal CO2 variability for a static location. Conducting such studies isn't particularly difficult, the cost of equipment is low, and it's an easy way to publish meaningful results. You may have a hard time wading through all of the publications to select the few that mean anything to you, specifically.

A quick 2 minute search found this paper (among a slew of others), entitled, Diurnal and Seasonal Variation of CO2 levels of surface air in Garwhal Himalaya
in which this graph highlights daily CO2 variations over the course of a year, in mmol/mol. You'll have to look up the conversion to ppm CO2:

You may to search using these key words: CO2 variability, diurnal, yearly
Seasonal and diurnal variations in moisture, heat and CO2 fluxes over a typical steppe prairie in Inner Mongolia, China

Temporal variations of atmospheric CO2 concentration in a temperate deciduous forest in central Japan

Seasonal and Diurnal CO2 Patterns at Diekirch, LU

Interannual variability in the atmospheric CO2 rectification over aboreal forest region


How do scientists know the precise location, etc. of the earliest supercontinents? Or their configurations far, far into the future?

Please take a look at this website, Dr Scotese explains what methods we use to determine how the earth was in the past, and indeed, what it might do in the future. We can never be sure however. He has also posted numerous videos on You Tube.
From Dr Scotese's website :

The past positions of the continents can be determined using the
following five lines of evidence: paleomagnetism, linear magnetic
anomalies, paleobiogeography, paleoclimatology, and geologic history.
Paleomagnetism is the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials. Magnetic minerals in rocks can lock-in a record of the direction and intensity of the magnetic field when they form. This record provides information on the past behavior of Earth's magnetic field and the past location of tectonic plates. The record of geomagnetic reversals preserved in volcanic and sedimentary rock sequences (magnetostratigraphy) provides a time-scale that is used as a geochronologic tool. By measuring the remanent magnetic field often
preserved in iron-bearing rock formations, paleomagnetic analysis can
determine whether a rock was magnetized near the Pole or near the
Equator. Paleomagnetism provides direct evidence of a continent's N-S
(latitudinal) position, but does not constrain its E-W (longitudinal)
position.
Linear Magnetic Anomalies. The Earth's magnetic field has another
important property. Like the Sun's magnetic field, the Earth's
magnetic field "flips" or reverses polarity. Fluctuations, or
"anomalies", in the intensity of the magnetic field, occur at the
boundaries between normally magnetized sea floor, and sea floor
magnetized in the "reverse" direction. The age of these linear
magnetic anomalies can be determined using fossil evidence and
radiometric age determinations. Because these magnetic anomalies form
at the mid-ocean ridges, they tend to be long, linear features (hence
the name "linear magnetic anomalies") that are symmetrically disposed
about the ridges axes. The past positions of the continents during the
last 150 million years can be directly reconstructed by superimposing
linear magnetic anomalies of the same age.
Paleobiogeography. The past distribution of plants and animals can
give important clues concerning the latitudinal position of the
continents as well as their relative positions. Cold-water faunas can
aften be distinguished from warm-water faunas, and ancient floras both
reflect paleo-temperature and paleo-rainfall. The similarity or
dissimilarity of faunas and floras on different continents can be used
to estimate their geographic proximity. In addition, the evolutionary
history of groups of plants and animals on different continents can
reveal when these continents were connected or isolated from each
other.
Paleoclimatology. The Earth's climate is primarily a result of the
redistribution of the Sun's energy across the surface of the globe. It
is warm near the Equator and cool near the Poles. Wetness, or
rainfall, also varies systematically from the equator to the pole. It
is wet near the equator, dry in the subtropics, wet in the temperate
belts and dry near the poles. Certain kinds of rocks form under
specific climatic conditions. For example coals occur where it is wet,
bauxite occurs where it is warm and wet, evaporites and calcretes
occur where it is warm and dry, and tillites occur where it is wet and
cool. The ancient distribution of these, and other, rock types can
tell us how the global climate has changed through time and how the
continents have travelled across climatic belts.
Geologic and Tectonic History. In order to reconstruct the past
positions of the continents it is necessary to understand the
development of the plate tectonic boundaries that separate continents
and bring them back together again. Only by understanding the regional
geological and tectonic evolution of an area can you determine the
location and timing of rifting, subduction, continental collision and
other major plate tectonic events.


Can we determine strike when dip is given? What about the reverse?

No. Strike is a line value whose direction is referenced with respect to true north. Dip can be any 0-90 degree angle (below horizontal) perpendicular to that line. It must be physically measured in the field....usually by some seriously underpaid graduate lackey.


What is the difference between nappe and thrust sheet?

Nappes and thrust sheets are very similar terms.

I agree with definition found on wikipedia:
(except for the 2 km requirement of movement, I would replace 2 km with significant distance.  I am sure you still have a Nappe with only 1.5 km of movement is measured.)

In geology, a nappe or thrust sheet is a large sheetlike body of rock that has been moved more than 2 km (1.2 mi) or 5 km (3.1 mi) above a thrust fault from its original position. Nappes form in compressional tectonic settings like continental collision zones or on the overriding plate in active subduction zones. Nappes form when a mass of rock is forced (or "thrust") over another rock mass, typically on a low angle fault plane. The resulting structure may include large-scale recumbent folds, shearing along the fault plane, imbricate thrust stacks, fensters and klippe.


Winds in a northern hemisphere hurricane

The winds in a hurricane move cyclonic and inward at the surface and anti-cyclonic and outward in the upper troposphere.

Cyclonic winds are counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere.  Anti-cyclonic is the opposite of cyclonic.

See this answer for a more detailed discussion of the winds within a tropical cyclone.


Sudden Localized Surface Water Temperature Increase In Eastern Lake Superior, Canada

NOAA revised the data.

The map below is for the same date and time as the first map in the question, but with the anomaly gone.  So I'll have to assume the event wasn't real.


How Can We Establish Precisely What Earth's Core is Made Of?

We know the density of the core from seismology.
We also know the density of pure iron at given pressure (P) and temperature (T).
From these two, people have long noticed that there is a discrepancy: the actual core is lighter than a theoretical core made of pure iron. This is known as the Core Density Deficit (CDD). To explain this CDD, we need to add light elements in the core composition. There are many candidates, such as sulphur, carbon, silicon, oxygen, etc.

This is actually needed by geochemists, who try to relate the Earth's composition to that of chondrite. They find that the Bulk Silicate Earth (BSE = crust + mantle) is depleted in some elements compared to the chondritic reference, and have to invoke a hidden reservoir to explain this. For some elements, this reservoir could be the core.

To further constrain this, petrologists run some high-P/high-T experiments to see the behaviour of elements during the Earth differentiation. Some elements are said to be lithophile, meaning they will stay in the BSE, while other elements are considered siderophile, hence should have joined the metal phase during segregation of the core. The problem is that some experiments disagree with others, as the behaviour of a given element can change depending on the conditions. For instance, niobium and tantalum are considered lithophile, but can be siderophile in reduced conditions.

I'm afraid the bottom-line of all this is: there is no simple answer to this question...


Ground water is almost every where, then how do mines and other holes are digged so that ground water doesn't drain into it

We pump it out. Open and closed pit mines usually have pumping installations to get the water out.

Look up Mine dewatering on Wikipedia.

There have also been numerous accidents in the past where mines were flooded (YouTube: Turkey mining accident: 18 workers trapped after underground water floods mine), and when left alone many abandoned mines will fill up with (ground) water.
Sometimes these are nice diving objects.

Or (as Trond Hansen commented) we try to prevent it from coming in in the first place, by using cement, grout or bulkheads to 'plug the holes'.

If you are really interested:

Mine Water: Hydrology, Pollution, Remediation by P.L. Younger, S.A. Banwart, R.S. Hedin.

Design of Water Holding Bulkheads for CoalMines by V.S. Mutton and A.M. Rememnikov


The mean direction of waves in a directional distribution

It is helpful to understand the meaning of Fourier coefficients in the directional wave spectrum analysis.

A pitch-and-roll buoy measures time series of water elevation $\eta$, and slopes in both Cartesian directions, $\eta_x$ and $\eta_y$. The Fourier components $a_0$, $a_1$, $b_1$, $a_2$, $b_2$, are related to cross-spectra of elevation and slope time series (introduced by Longuet-Higgins 1963):

$$
a_0 = \dfrac{C_{11}}{\pi}
$$

$$
a_1 = \dfrac{Q_{12}}{\pi}
$$

$$
b_1 = \dfrac{Q_{13}}{\pi}
$$

$$
a_2 = \dfrac{C_{22}-C_{33}}{k^2\pi}
$$

$$
b_2 = \dfrac{2C_{23}}{k^2\pi}
$$

where the cross-spectra are:

$$
C_{11}(f) = C[\eta(f)\eta(f)] = \int_0^{2\pi} E(f,\theta)d\theta
$$

$$
Q_{12}(f) = -Q[\eta(f)\eta_x(f)]k^{-1} = -\int_0^{2\pi} E(f,\theta)\cos{\theta}d\theta
$$

$$
Q_{13}(f) = -Q[\eta(f)\eta_y(f)]k^{-1} = -\int_0^{2\pi} E(f,\theta)\sin{\theta}d\theta
$$

$$
C_{22}(f) = C[\eta_x(f)\eta_x(f)]k^{-2} = \int_0^{2\pi} E(f,\theta)\cos^2{\theta} d\theta
$$

$$
C_{23}(f) = C[\eta_x(f)\eta_y(f)]k^{-2} = \int_0^{2\pi} E(f,\theta)\sin{\theta}\cos{\theta} d\theta
$$

$$
C_{33}(f) = C[\eta_y(f)\eta_y(f)]k^{-2} = \int_0^{2\pi} E(f,\theta)\sin^2{\theta} d\theta
$$

From here you can see that the mean direction, as defined in the paper that you cite, is:

$$
\theta_0 = \arctan\left({\dfrac{b_1}{a_1}}\right) = \arctan\left({\dfrac{Q_{13}}{Q_{12}}}\right) = \arctan\left({\dfrac{\int_0^{2\pi}E(f,\theta)\sin{\theta}d\theta}{\int_0^{2\pi}E(f,\theta)\cos{\theta}d\theta}}\right)
$$

Because $Q_{12}$ and $Q_{13}$ are proportional to the integrated energy in the zonal and meridional directions, respectively, the arctangent of their ratio yields mean wave direction.

The authors could use higher moments to calculate direction, but this would have different physical meaning. In this specific case, using $\theta = \arctan\left({b_2/a_2}\right)$ would yield peak (dominant) wave direction in the context of pitch-and-roll buoys.

You see that the above analysis is inherently limited by the quantities that are measured, specifically $\eta$, $\eta_x$, and $\eta_y$. If higher order quantities, say $\eta_{xx}$, $\eta_{xy}$, $\eta_{yy}$ were available, the directional spectrum could be described at a higher accuracy even using just Fourier decomposition.

Further reading:

Oltman-Shay and Guza (1984)
Nondirectional and directional wave data analysis procedures at NDBC


The formula you found comes from the barometric formula. It assumes a hydrostatic atmosphere (no vertical accelerations), a constant temperature with height (or a mean temperature) and uses the ideal gas law:

$$h= -\frac{RT}{g} \cdot \log \frac{p}{p_{sfc}}
$$
where h is height above ground, R is the ideal gas constant, T is the mean temperature, g is the gravitational constant, p is the pressure of the cloud top in your case and $p_{sfc}$ is surface pressure (not reduced)

The first factor comes down to a value of $-8$km if $T \approx 273$ K. This value is also known as scale height. $p_{sfc}$ is approx. 1013 hPa if you're at sea level.

So LOGS would most probably mean the natural logarithm.

I don't think there is a simple equation for the cloud top height from ground observations because e.g. how high a cumulus grows depends on the temperature of the surrounding air.

Cloud base height and cloud top height are two totally different things. The cloud base height formula does not depend on the on the upper air temperature.

Whether a thermal (which evolves into the cloud later on) reaches its cloud base or not, is not sure. As long as it's warmer than its surroundings, it rises. The same for the cloud: It rises up as long as it is warmer than its surroundings. You may know what's the temperature of the cloud at each height, but how cold the air at, say 15,000 ft is, varies a lot.


Does a hurricane with a smaller eye have a lower pressure?

I could only find this old reference(30 years old) Typhoon Structure As Revealed By Aircraft Reconnaissance. Part 2: Structural Variability by Weatherford And Gray 1988.

The conclusion of the authors is that the size of a tropical cyclone's eye does not have much of a observable relationship with the cyclone central pressure(MSLP) and is shown as a weak correlation. Observations reveal that the contracting eye size of a TC on the average is associated with a decreasing MSLP and an expanding eye size is associated with a increasing central pressure.

So let's look at some actual numbers from that above paper -

These are again averages for the period 1980-82 tropical cyclones that have been classified on the basis of size of the eyewall

Eye-class                          MSLP(Central pressure in mb)  MSLP Change(in mb/12 hrs)

No eye                             985                            +/-5

Large eye ( > 28 kms)              987                            +/-8

Medium eye (15-28 kms)             956                            +/-9

Small eye ( < 15 kms)              954                            +/-12

Note from this table how much the MSLP fluctuates over a period of 12 hours  for the smaller eye sizes. Also remember that a vast number of cyclones do not form eyes.

Word of caution if you are trying to view this table from the operational forecaster's point of view it is very likely an individual cyclone may depart from these average values. And while these data sets have been obtained for the Northwest Pacific Ocean it is likely they hold up for other basins as well.