Why can I look directly at the sun during a sunset but not at noon?

At Noon, sunlight is coming from nearly directly above you, and goes through ~2 miles (4km) of reasonably dense atmosphere to reach you (Atmospheric pressure at 2 miles is about one half of sea level pressure). At sunset (and sunrise), since the sunlight is traveling mostly parallel to the surface, it travels through dense atmosphere for considerably longer. When traveling through dense atmosphere it's subjected to more scattering, which decreases the observed intensity of the light.

Or, considered a different way, when looking at a sunset/sunrise, you don't see the sun as a single well defined point. It's hazy, with the bits of sky near to the sun also giving off a fair amount of light. That additional light is some of the light that was scattered from an otherwise direct beam. If it were all re concentrated to a single point, it would be brighter/more painful to look at (though not as bright as the noon sunlight- for shaky statistical and light absorption reasons).

Using an Earth Curvature Calculator, sunlight at the horizon travels through ~120 miles of 'dense' atmosphere (ie has an altitude <2 miles). That will fall off rather quickly the higher above the horizon the sun is.

(dense atmosphere in this refers partly to just thicker air; but also to particulates/dust in the air, haze, mist, fog, etc)


Why do anticyclones bring clear skies in summertime?

Why anticyclones are also called areas of high pressure

Let's call anticyclones areas of high pressure.

Areas of high pressure (anticyclones), pull air towards the earth's surface. The increase in the number of air particles near the earth's surface causes a higher pressure for things on the earth, hence the name.

Impact of high pressure areas on weather

High-pressure areas don't always bring hot weather.

High pressure areas do prevent the chances of clouds forming. Why? Because more air is pushing down around the earth's surface, rather than rising up in the air where it can cool and form clouds. This is why areas of high pressure (anti-cyclones) bring clear skies.

Because high-pressure areas prevent clouds forming, this can cause hot fine weather in summer when the temperatures are warm and sunny days are long, or cold weather in winter, when sunlight hours are short and the lack of clouds means any warm can escape from earth's surface and back out into space.

Background info on clouds and heat

Heat generated by the sun travels two ways:

Towards Earth: From the sun, through space, hitting the earth
Away From Earth: From the earth and back out into space

Clouds reflect heat.

Either away from earth, as incoming sunlight hits the tops of
clouds, or
towards earth, as heat radiating away from earth's surface towards space hits the bottom of a cloud and bounces back

Areas of high pressure stop clouds from forming, which can mean warm summer days or cold winter days for the reason above! (In summer, a lot of sunlight can get through to the earth's surface, in winter when there's little sun, any of the earth's heat escapes into space with no cloud to stop it!)

I presume you are a beginner, so I've given a basic and easy to understand answer. Once you wrap your head around this, I can update with more details.


Are there websites where I can get "lightning frequency maps" in near-real time (worldwide)?

Absolutely: The Blitzortung project has near real-time data for most if not all of the world.

I've also never taken the time to research how lightning detectors exactly work, but it's likely similar... and you can read about the Blitzortung instrument here.

Windy.com also appears to now have lightning data over at least the largest part of the globe (perhaps using the Blitzortung source).  And though it's not for your region, GOES new satellites also have a lightning detector on them, which you can view at some data from on any of the GLM links on this page.


Convert satellite image data (GOES 15) into solar irradiance values?

It is far too complex a process to estimate surface irradiances utilising satellite data. No software takes just satellite images as input and gives out irradiances.

I am pasting link to an article that describes algorithm to convert geostationary satellite measurements to surface reaching solar irradiance.

Gadhavi et al., 2008; doi: 10.1029/2007JD009308

To summarise following are most important aspects in estimating surface radiation budget.

Calibration constants to convert photon counts measured by satellite sensor to radiance
Parameterisation scheme to convert narrow band satellite radiances to broadband radiances.
surface optical characteristics as function of wavelength, sun elevation and season
Geophysical parameters like cloud amount, aerosol amount, ozone, etc. (Essentially these are the real satellite input in whole process).
Radiative transfer model to estimate irradiances using inputs received from satellite and other sources.

There are few web-site where one can directly get final output of irradiance values. See following link.
https://data.noaa.gov/dataset/surface-radiation-budget-surfrad-network-1-hour-observations


What were the tallest mountain ranges in Earth's geological past?

Factors determining the maximum possible height of mountains include the rate of uplift versus the rate of erosion[a] and rock strength.

Rock strength is controlled by the type and internal structure of the rock in question. There is some evidence that once mountains extend above the snow line, glacial and periglacial erosion have a stronger control than exhumation/uplift rate (Brozovic et al, 1997; Egholm et al, 2009).

Everest and the Himalaya have reached their maximum possible elevation: the formation of the Tibetan plateau is due to the failure of rocks preventing the maintenance of discrete mountain peaks. The principle of uniformitarianism suggests that - subject to differences in variables discussed by Egholm et al, including crustal composition - the Himalaya and Tibetan plateau are an excellent approximation to the maximum achievable height of mountain ranges. However, identifying which specific palaeoranges were tallest (as opposed to calculating a plausible upper limit on height) is a significantly harder problem to solve.

[a] Though note that the rate of erosion increases as the rate of uplift increases - for more on erosional equilibrium, see e.g. Riebe et al (2000).


How much is Iceland/Norway/Western Europe warmed up by the Meriodional Overturning Circulation?

To answer the numerical aspect of your question: Rintoul & Wunsch 1991 advanced a poleward heat flux in the North Atlantic (i.e. that generated by the Gulf Stream) of $1.3\pm0.2\times 10^{15}W$.

That number of 1.3 PW (PetaWatts) have been reused in several reviews on the thermohaline circulation such as Clark et al. 2002; hinting that this number is at least realistic (since I'm not a physical oceanographer myself it is difficult for me to judge otherwise).

References:
Clark, P. U., Pisias, N. G., Stoecker, T. F., Weaver, A. J. 2002. The role of the thermohaline circulation in abrupt climate change. Nature, 415: 863-869.
Rintoul, S. R., Wunsch, C. 1991.Mass, heat, oxygen and nutrient fluxes and budgets in the North Atlantic Ocean. Deep Sea Research Part A, 38: S355–S377.


Prior to the New Horizons flyby, a popular model for Pluto’s surface involved frost migration. Delsanti & Jewitt (2006) explain that at different points during the year, there should be seasonal pressure variations in the atmosphere. This then causes changes in the extent of nitrogen and methane ices on the surface, which over long periods of time - remember, Pluto has a very long period of revolution - alters local geography. The authors also mention cryovolcanism as a potential source for replenishment of methane that is destroyed by cosmic rays.

Trilling (2016) discusses cryovolcanism and two other processes as ways to resurface Pluto and remove craters:

Viscous relaxation. Ices on the surface “flow”, removing certain surface formations.
Convective overturn. Temperature differences in convective cells cause flows similar to those in viscous relaxation.
Cryovolcanism. In addition to releasing methane (and potentially nitrogen), cryovolcanism can heat up parts of the surface, melting ices, which then erode features.

So far, two cryovolcano candidates have been tentatively identified, Piccard Mons and Wright Mons:

Image from Nature; image credit NASA/SWRI/JHUAPL.

The cryovolcanic situation on Pluto may be closer to that of Enceladus than that of Europa. Plumes were observed on Enceladus’s south pole by Cassini, which appear to be cryovolcanic in nature:

False color photograph of Enceladus’s south pole jets. Image in the public domain.

Tidal heating is thought to be a large contributor to the heat necessary to trigger the plumes. However, this is likely not enough. One explanation is the hot start model, popular for many years, in which Enceladus initially generated enormous internal heat through the decay of radioactive isotopes of aluminum and iron. Other elements that are slower to decay could then have provided more heat as the aluminum and iron stopped producing heat. The subsurface ocean that may have resulted on Enceladus could also exist on Pluto, according to Hussmann et al. (2006).

This is only one possible explanation for a heat source to power cryovolcanism, but there does need to be some sub-surface process on both Enceladus and Pluto that can cause these effects. The hot start model is a good option.


How is global weather model skill measured?

There are lots of articles that assess global models both locally and globally. They usually focus on a few parameters that are easily comparable with observations (e.g., temperature, wind, surface pressure). A couple of examples of the many available:

for ECMWF:

Roberto Buizza, 1997: Potential Forecast Skill of Ensemble Prediction and Spread and Skill Distributions of the ECMWF Ensemble Prediction System. Mon. Wea. Rev., 125, 99–119, doi: 10.1175/1520-0493(1997)125<0099:PFSOEP>2.0.CO;2.
for both only looking at precipitation:

Thomas M. Hamill, Renate Hagedorn, and Jeffrey S. Whitaker, 2008: Probabilistic Forecast Calibration Using ECMWF and GFS Ensemble Reforecasts. Part II: Precipitation. Mon. Wea. Rev., 136, 2620–2632, doi: 10.1175/2007MWR2411.1.
For the climate model world, check out: http://www-pcmdi.llnl.gov


Is there a theory on how the Earth's plates were initially formed?

The answer to this is has roots in another question you asked about the differences between continental crust and oceanic crust. Carlson et al. (2014) just put out an excellent review of what we know about Earth and how it formed through time. I am using it as a guide and source for much of this post.

Just recently an age of a zircon was determined to be 4.374 Ga (Valley et al., 2014) using U-Pb geochronology. The age of the Earth is 4.54 ± 0.05 Ga. This new result suggests that granitic and felsic magma was already present on Earth only after ~160 million years after the Earth formed. Some other interesting dates is the Moon formation between 4.4 to 4.45 Ga and, based on xenon isotopes, the separation of the atmosphere from the solid Earth is thought to happen around 4.45 Ga.

After the formation of the Earth, the core formed, thereby creating a metallic inner core and the primitive outer mantle. The Earth began to cool and differentiate and thereby form a crust. Different models suggest a range of possibilities such as a quasi-stable quench crust of peridotitic/komatiitic composition (Smith, J.V., 1981) to a very evolved composition approaching tonalite (Harrison,T.A., 2009).

The question now is this crust now a plate or rather, similar to the lithosphere as we know it today?  The lithosphere is defined as the brittle outer layer of the Earth and plates are segments of the lithosphere and the base of it is called the Mohorovičić discontinuity, which generally defines the contact between the lithosphere and the upper mantle. It is interesting to think about when these features may have formed as the Earth's outer crust is forming.

There is an entire GSA Special Paper volume on the subject of 'When Did Plate Tectonics Begin on Planet Earth?'. There is a range of evidence suggesting that plate tectonics as we know it today initiated at the latest around ~3 Ga to as late as ~1 Ga (Condie & Kröner, 2008). Below is a table from that paper that outlines indicators of plate tectonics.

The outer crust of Earth is likely not stationary, but possibly being dragged along the paths of mantle convection. These brittle segments begins colliding into one another and building upwards while other portions are subducted beneath other plate segments. The convecting mantle causes mantle material to be brought up from depth to conditions at lower pressures, which cause the mantle to melt (this is called adiabatic melting).

There was a paper just recently published in Nature by Bercovici and Ricard(2014) where they try to answer the question as to why we see geological evidence of proto-subduction at 4 Ga with for prominent subduction features appearing around 3 Ga. I suggest reading the abstract on the papers website but they suggest that ...

  when sufficient lithospheric damage combines with transiet mantle
  flow and migrating proto-subduction, it leads to the accumulation of
  weak plate boundaries and eventually to fully formed tectonic plates
  driven by subduction alone. - Bercovici and Ricard (2014)

On the composition of the crust...

The most incompatible elements in the mantle (e.g. lithophile elements [K,Na, Nd] and high field strength elements [U,Th]) will go into the liquid melt and move towards the surface of the Earth and either erupt on the surface or be stored in a magma chamber and further fractionate or differentiate to more felsic magma compositions.

Through time, all of these processes will generate different pieces of crust formed from different sources and at varying conditions and later become altered due to either chemical or physical metamorphism. Each of the continents we have today are pieced together from the separation and collision of other tectonic plates. For example, Pangaea was formed due to the collision of many different plates, I am not sure if Pangaea was then considered one giant plate, but it then broke apart and separated.

  Is it possible for existing plates to split into two distinct plates?

The East African Rift is currently a divergent boundary within the African Plate. So the answer is yes.


Why does the meandering pattern of the jet stream itself propagate?

I wouldn't characterize the movement of the jetstream as a "less well known" problem, at least not to anyone who has sat through a synoptic meteorology class.  The jetstream from a dynamic point of view is just an enhanced gradient in the heights on a constant pressure surface (or pressures on a constant height surface) and there are many factors the influence this gradient.

First, lets take a look at the northern hemisphere 500 mb heights and surface pressure:

What we see here is in the mid-latitude storm track we have a series of highs and lows on the 500 mb surface (blues are low anomalies, red high anomalies).  This particular pattern look to be wavenumber 7,  This is a planetary rossby wave. If the weather was frozen in place and all external factors eliminated, the wavenumber is going to dictate how fast this pattern rotates around the globe.  For low wavenumbers, this pattern will even move retrograde, but that is not something you see often (if memory serves, this is wavenumber 3 and lower).

You might wonder why I'm talking about waves at 500 mb when the polar jetstream is up a bit higher between 250 and 300 mb, varying seasonally.  The pattern of highs and lows is evident throughout the troposphere.  You can see it reflected in the surface pressure and in the image below you can see it in the 300 mb pattern.

So far we've mentioned that the wavenumber of the planetary wave has an influence on movement of the pattern, but what about how the pattern evolves?  There are a lot of factors here:

Oceans
Mountains
Surface heating
Convection

And perhaps the biggest:

mid-latitude cyclones.

Part of cyclone self development is a positive feedback between surface temperature advection and pressure changes at the tropospheric mid levels.  As the cyclone matures the advancing surface cold front will correlate with low 500 mb heights and lower 300 mb heights.  This response will perturb where the jetstream lies and indeed, the jetstream tends to lie over the fronts extending from a mid-latitude cyclone.  If you conceptualize the fronts from one cyclone extending back and forward to the cyclones next to it, this is the "polar front" and gives you a rough idea of where the jetstream is.

An additional factor in how the jetstream propagates is the particular shape of the jetstream.  There are a number of blocking patterns (e.g. Omega block, Rex block) that tend to persist as a stationary feature once setup.

Finally, remember that in an atmospheric column, pressure is just the weight of all the air above a height, and anything that can modify the column (e.g. surface heating, cooling, mid-level changes) can modify the 300mb heights and subsequently affect the positioning of the jetstream.


How would Earth map look like if all ice melts?

Calculated Earth is one of the better tools for this, you can either zoom in and get various flood stages or set a specific flood stage and see what would flood, it is in metric though so you may need some conversion software to deal with the units for you, depending how familiar you are with metric.


How Can Adjacent Parts of an Oceanic Plate be Subducted in Different Directions?

Where one part of a plate continues almost horizontally while an adjacent section is driven down into the mantle, wouldn't that cause a violent fracture of the plate, and if not, why not?

In case of the Nazca plate probably not because that is still warm and partly ductile (see the linked work in the other thread). Also, these cracks and deformations happen as the plate subducts, they don't displace a huge pile of material in one single event, like does a movement along a transform crack (e.g. San Andreas), or a "megathrust" earthquake along a subduction zone. A whole plate breaking along the bend line otoh can trigger catastrophic earthquakes.

I could not find a specific work that deals with the interface between a steep and a shallow subduction, but a work discussing the dynamics of the Nazca plate subduction. They state that the ridges (being warm and buoyant) are subducted because of the movement of the adjacent slabs (dragged along so to say), and becaue of global plate motion, meaning the earth can't change volume so some parts just must give way for emerging parts elsewhere (Atlantic opening is mentioned). There is a map of epicenters of (generally low mag) earthquakes (and links to other work) along the Nazca subduction as well as above the flat segments, suggesting that the cause there is the greater friction. The oceanic crust, being quite topographic, is flattened while being pushed or drawn under the continent.

Earthquakes because of segmenting as asked in the OP aren't mentioned specifically.

I find it interesting, maybe someone else knows more.


What Caused The Sea Levels to Drop During the Maastrichtian Epoch?

Tectonic activity can change the volume of oceanic basins and hence, modify the sea level, ice not involved.

Firstly let's explain the left picture.

At Cretaceous the tectonic activity was high. The flux of material from mantle to ocean ridges and plateaux reduced the volume of ocean basins, wich produced a global high sea-level observed in differents parts of the globe.

During Campanian and Mastrichtian global transgressions are recognized in several stratigraphic sections of the Earth.

Z. Dubicka and D. Peryt (2012) studied a stratigraphic sequence in Poland wich also showed transgression phases on Mastrichtian. They correlated them with other strata of the age.

  This sea-level rise, recorded in south-eastern Poland, can be
  correlated with the transgressive peak recognized by Hancock (1993);
  this corresponds to the Craise Graise (¼ Vijlen Member) exposed in the
  CPL quarry at Halembaye in Belgium, which in turn corresponds to the
  lower Belemnitella junior Zone, i.e., earliest Late Maastrichtian.
  Hancock (1993) suggested that this peak may occur globally. He
  correlated it with the Prairie Bluff Chalk on the northern margin of
  the Gulf of Mexico and with strata that lie a little above the base of
  the Tinton Greensand on the Atlantic coastal plain. The transgressive
  peak in the earliest Late Maastrichtian was also documented in the
  Sopelana section in the Basque Arc Domain in Spain (Gómez-Alday et
  al., 2004), which coincides with the inoceramid extinction, the
  informal definition of the Lower/Upper Maastrichtian boundary.
  Moreover, a marked transgression in the middle Maastrichtian was
  reported from the Southern Hemisphere by Huber and Watkins (1992) who
  noted a higher diversity of keeled foraminifera, which they
  interpreted as reflecting a possible transgression.

Then let's focus in your question about the sea level drop. It is pretty obvious a regression happened, at least at North America.

The sea level drop appears to be global too, according to Matsumoto (2002) and associated to a slowing down of global tectonic activity.

  Tectono-eustasy may have been the main cause of the phenomena of
  transgression-regression, but certain kinds of other tectonic
  movements which affected even the so-called stable platforms were also
  responsible for the phenomena. The combined effects of various causes
  may have been unusual in the Cretaceous, since it was a period of
  global tectonic activity. The slowing down of this activity followed
  by readjustments may have been the cause of the global regression at
  the end of the Cretaceous.

Zofia Dubicka, Danuta Peryt (2012): "Latest Campanian and Maastrichtian palaeoenvironmental changes: Implications from an epicontinental sea (SE Poland and western Ukraine)", Cretaceous Research
Volume 37, October 2012, Pages 272-284.
https://doi.org/10.1016/j.cretres.2012.04.009

T.Matsumoto (2002): "Inter-regional correlation of transgressions and regressions in the Cretaceous period", Palaeogeography, Palaeoclimatology, Palaeoecology. Volume 187, Issues 1–2, 1 November 2002, Pages 35-60
https://doi.org/10.1016/S0031-0182(02)00504-7


Is it possible that water (H2O) was made on earth?

This is more Astronomy than Earth Science, but the Young Earth, while forming, would have had a hard time retaining Hydrogen.   There's two reasons for this.   One is the Frost Line which means there was relatively little hydrogen and relatively little water and other gases present when the Earth formed.

And the other is Atmospheric Escape.  The Earth doesn't have enough gravity to retain Hydrogen.  In fact, the Earth is still losing Hydrogen, by this estimate, about 95,000 tons per year.

Precisely how much hydrogen and water the Earth contained at formation vs how much it acquired by solar wind (Hydrogen nuclei) and comet and asteroid impacts (water and other gases) isn't known.  I think it's likely that the majority came from impacts and I think that's where the consensus leans, but an precise answer isn't known.

As far as the Earth combining Hydrogen with Oxygen, there's relatively little free Oxygen in the solar-system.  Oxygen binds easily with many elements, so it's abundant but not in it's elemental/gaseous state.  The Earth also tends to lose gaseous hydrogen and not having Oxygen until about 2 billion years ago, it's unlikely that much water was formed in that way.

When we learn more about exoplanets, we might find that larger/super Earths might retain more hydrogen and form abundant water in that way if they have photosynthesis to create Oxygen, but that's just theoretical.  Earth is too small to have retained enough hydrogen to do that in large amounts.


Is this XKCD comic an accurate timeline of the earth's average temperature?

Yes, it's accurate, see e.g. this picture taken from the Wikipedia Geologic temperature record page:

You could dig up the source if you wanted from the wikipedia article (or the graph description page), but any graph will be generally the same. Since there was an ice age, you'd expect global temperature to be low ~20k years ago and so on.


Why is a seismogram interpreted as a convolution?

In simplest terms, it simply means that:

if the source signal is shifted by some amount of time Δt, but otherwise unchanged, then the seismogram will also be shifted by Δt, but otherwise unchanged; and
the seismogram generated by the sum of two (or more) source signals is the sum of the seismograms that would've been generated by each of the individual source signals.

Basically, it works exactly like an ordinary echo: what you hear is the original sound, or rather several overlapping echoes of it, each reaching you by a different path, delayed and attenuated by varying amounts during its propagation.

Mathematically, this process can be represented by convolving the source signal waveform with a function, called the convolution kernel, that describes how the signal is spread out and split into multiple echoes.  Specifically, the convolution kernel is northing more or less than the waveform of the echo that would, in principle, be produced by an "ideal unit impulse" source signal — that is to say, a source signal consisting of a single, infinitesimally short pulse of sound pressure carrying one unit of energy.  For this reason, the convolution kernel is also known as the impulse response of the system.

The convolution process itself, in the simplest case, merely amounts to summing together several shifted and scaled copies of the impulse response.  Specifically, this is the case when the input signal can be represented (or at least approximated) as a sum of several pure impulses.  More generally, any input signal can be mathematically represented as a sum — or, more properly, an integral — of infinitely many tiny impulses spaced infinitely closely*, in which case the resulting seismogram is simply the integral of infinitely many infinitely small shifted copies of the impulse response.  This is precisely what a convolution does.

*) Mathematicians, and perhaps some physicists, reading this will cringe at this point; while a sum of impulses can indeed approximate any function as a measure in the weak sense, it's not a good approximation is most other senses.  Nonetheless, it is a rather useful and concrete way to think about convolutions.

One reason why thinking about seismograms as convolutions is useful is that, if we know the physics of seismic propagation and the geological structure of the area through which the signal propagates, we can calculate the theoretical impulse response function of the system and convolve it with a simulated source signal to obtain a synthetic seismogram.  Conversely, given a real seismogram and the source signal that produced it, we can deconvolve them to obtain an approximation of the impulse response, which can then yield tomographical information about the geology.


Negative values of relative humidity in CFSR

I am also getting negative relative humidity from the GFS (Global Forecast System): 36-hour predicted atmosphere dataset (Provider: NOAA/NCEP/EMC, their website: http://www.emc.ncep.noaa.gov/index.php?branch=GFS)

I found this link that answers as to why relative humidity is possible in their dataset:

http://ftp.cpc.ncep.noaa.gov/wd51we/reanal/random_notes/negative.h2o

This might apply to the one you have access too.

Let me know if this helps.


Where can I find wave height/period, current velocity and wind speed/direction data at the Qiangzhou strait in China?

You can retrieve that information from ERA5 reanalisys data. It cover the whole world from 1979 until almost the present. The resolution is 0.25°x0.25° and includes many fields that characterize ocean waves. here is a list of available fields for download in the "Ocean Waves" section:

And there is of course, winds data as well.


Eliminating range folding error in doppler radar returns

Frequency

Most high-power radio-frequency amplifiers (klystrons, cavity magnetrons) have a very limited frequency range.  A dual-frequency radar would essentially be two radars hooked up to the same antenna.

Polarization

Horizontally-polarized radar waves reflect more strongly from the ground than vertically-polarized waves, while circularly-polarized waves reflect only weakly from rain.  Consequently, vertical polarization gives the best results for weather radar.  A dual-polarization radar would sacrifice detail to eliminate range error.


What caused the Carbon Dioxide Variations observed in the 800,000-year polar ice record?

This article investigates the ocean's dissolved carbon content (ocean reservoir) and the seafloor's methane hydrates ("methane ice") as a source of CO2 fluctuations in ice cores. They discuss three ways the ocean may release CO2.

through physics (changes in temperature and ocean currents)
biologically or chemically
through general climate changes

Hope this helps.


Why don't they give hurricanes uncommon names?

It's just the system that is used.

The first person to give names to cyclones/typhoons/hurricanes was Clement Wragge, an Australian weather forecaster in the 19 century.

  He first designated tropical cyclones by the letters of the Greek alphabet, then started using South Sea Island girls' names. When the new constituted Australian national government failed to create a federal weather bureau and appoint him director, he began naming cyclones "after political figures whom he disliked. By properly naming a hurricane, the weatherman could publicly describe a politician (who perhaps was not too generous with weather-bureau appropriations) as 'causing great distress' or 'wandering aimlessly about the Pacific.'

During World War 2, US army & navy meteorologists name tropical cyclones after their wives, after having been introduced to a novel, Storm, in which a junior meteorologist named extra-tropical storms after girl friends.

In 1947 the US Air Force Hurricane Office in Miami started using the then new international phonetic alphabet (Able, Baker, Charlie, ...) when naming hurricanes in the North Atlantic Ocean.

When the international phonetic alphabet changed in 1952 (to Alpha, Beta, Charlie ,..) The US Weather Bureau initially started using the armed services practice of using women's names.

In 1975 the Australian Bureau of Meteorology started using a system alternating womens and mens names. After political pressure, in 1979 by the

  US National Hurricane Center (NHC) requested that the WMO's Region IV Hurricane Committee switch to a hurricane name list that alternated men's and women's names following the practice adopted by Australia's Bureau of Meteorology in 1975.

IN the North West Pacific, womens names were first used in 1945. Mens names started being used in 1979. Now they use a series of Asian names, contributed by nations and territories that are members of the WMO Typhoon Committee.


Eureka! I and my prof figured it out. We found something interesting - that the energy density actually depends on a number of internal variables, namely, the displacements of the outer and inner walls, and porosity (which we already knew). So, when we specified the outer displacement to always be a fraction of the radius of the outer sphere, that seemed to fix the problem.

Thanks to all who attempted to help me out! :)


Can a person's individual carbon emissions become negative over their lifetime?

Aussies emit ~15 tonnes CO2 per capita per year. Current carbon capture and storage technology can bury CO2 for \$40-\$57 per tonne (estimate for early 2020s). So, yes, you could do this for ~$50,000 .
Underground storage is relatively permanent. As for trees, you could plant one of these,

1,700 tonnes  CO2 and lives 3,000 years. With any kind of trees you will need to assure your patch of forest remains treed for millenia. As for the number of trees, I think forested area is a better measure:

Approximative values of the carbon content (tonnes per hectare) for various vegetation types.
Source : IPCC, 2001

You would need tens of hectares.


You cannot leave "temperature outside", as temperature is the key factor to know if the balloon would pop or not.

Let's set up some assumptions about the problem so we can calculate something:

The gas inside the balloon behave according the ideal gas law: $PV=nRT$
That the balloon can hold a differential pressure of 30 mmHg (=4000 Pa) as found in this experiment.
That the maximum volume of a balloon is 0.015 m$^3$ as suggested here.
The balloon starts filled to its maximum size.

With this we can calculate how many moles of gas the balloon can hold when inflated in space at a given temperature.

For the temperature I'll assume it will be something between the temperature of the cosmic microwave background radiation (if it is on the shade) of ~2.7 K (-270 °C), and the temperature that a black body that is illuminated by the Sun near Earth's orbit, which would be about 278 K (about 5°C). This assumes that the balloon is small enough so that heat can be transferred efficiently by diffusion from one side to the other (the calculation of this value can be seen in the code at the end and is based on the equation here).

With this range of temperatures we can find the volume of the balloon on the surface assuming a final pressure of 1 atm (101325 Pa) and a temperature of 15 °C.

We get the following relationship:

In red are the final volumes for which the balloon would explode and in blue when it wouldn't. The critical temperature in between is -262 °C (~11 K).

Therefore, the balloon would not pop as long as its initial temperature is higher than -262 °C.

This also assume that the hottest point in the trajectory is the surface. This means that we are assuming that the balloon will pass through the thermosphere fast enough to do not reach thermal equilibrium with it (it can be extremely hot). This could be a reasonable assumption given the very low density of that layer.

Of course this also assume the rubber of the balloon do not change its properties with temperature.

So, only once you specify the height at which you release the balloon and its initial temperature, then you can start calculating fall time. And that will be more difficult, because even if you assume the balloon is at free fall terminal velocity the whole time,  this velocity will change along the fall line due to changes air density and balloon size. Air density and balloon size will affect air resistance and, therefore, terminal free fall speed. You will need to do an analytical or numerical integration of the fall to get the total time.

Matlab code used to generate the above figure

R=8.3145;%Ideal gas constant [J/mol K]

Lsol=3.828e26;%Solar luminosity [W]
Dsol=149597870700;%Distance earth-sun [m]
sigma=5.670373e-8;%Stefan–Boltzmann constant [W m^-2 K^-4]
alpha=0;%albedo
epsilon=1;%emissivity
% Temperature of a black body (rotating or small enough to transfer heat efficiently from the illuminated side to the dark side)
Tbb=((1/4)*((Lsol*(1-alpha))/(4*pi*epsilon*sigma*(Dsol^2))))^(1/4);

% Temperature range
T=linspace(2.7,Tbb,1000);%[K]
Vmax=0.015;% Exploding volume [m³]
Pspace=4000;%Maximum pressure hold by the balloon [Pa]
n=Pspace*Vmax./(R*T);% number of moles that the balloon would hold
Patm=101325;% Atmospheric pressure [Pa]
Tsurface=15+273.15; % temperature at the surface [K]

% Volume once back on earth surface
Vfin=n*R*Tsurface./Patm;

explodeIdx=Vfin>Vmax;
Tlim=find(explodeIdx,1,'last');

figure('Color','w');
hold on
box on
plot(Vfin(~explodeIdx)*1000,T(~explodeIdx)-273.15,'b','LineWidth',2);
plot(Vfin(explodeIdx)*1000,T(explodeIdx)-273.15,'r','LineWidth',2);
plot([0 max(Vfin)]*1000,[1 1]*T(Tlim)-273.15,':r','LineWidth',2)
ylim([0 max(T)]-273.15);

xlabel('Final volume [liters]')
ylabel('Initial temperature [°C]')


What is the lateral ground acceleration, at the fault line, during a strike-slip earthquake?

It can be high but is bounded because the slip velocity on fault (as it slips during an earthquake) is usually of the order of 1-3 m/sec.

Kaikoura earthquake (M7.8 strike slip event) had a max PGA of 3.1 g (second highest ever recorded) but it is attributed due to flapping effect. See here for more details.


How does the influence of clouds on climate vary with height?

There are a few things that come into play when you talk about the radiative forcing of clouds, or their effect on the climate budget. "Cloud" is a pretty wide-sweeping definition. Scientists are still trying to fully understand and quantify these effects. Clouds do not vary only in where they are in the atmosphere but also in their phase (ice versus mixed phase versus water) and their depth--the combination of these two affect the cloud's optical depth. All of these different properties affect the net effect (whether positive, negative, or neutral) of clouds on the climate system.

High clouds are generally ice crystals, yes, because they are in areas of the atmosphere that are far colder than the freezing level. They are also generally geometrically thin. These high clouds have little effect on the shortwave energy and instead mainly reduce the amount of longwave radiation leaving the planet.

Clouds in the middle parts of the atmosphere are usually tall cumulus clouds that are full of liquid and mixed phase precipitation. These will be very bright to shortwave radiation and thus reflect much of that incoming radiation. They also provide some trapping of longwave emission from the surface and radiate less longwave radiation for a given level in the atmosphere than would normally be the case. The anvil regions of these clouds, on the other hand, are full of ice crystals which again don't reflect much shortwave radiation but do reduce the amount of longwave radiation leaving the planet.

Compared with the high atmosphere, completely ice phase clouds near the surface are thicker and their shortwave reflection is therefore a bit stronger than their thinner counterparts in the middle and upper atmosphere; they also trap longwave radiation from the surface. Mixed and liquid phase clouds' effects have similar effects as ice phase but are stronger in both the short- and longwave spectra.

Another thing special about clouds near the surface is because of that proximity they can actually have a strong influence on the surface which can cause a climate feedback. If you have a deck of clouds overlying a bright surface, it can actually warm the surface a bit since it is reflecting less shortwave than the highly reflective underlying surface would otherwise. For example, it has been hypothesized that the Greenland Ice Sheet melting is enhanced when cloud cover is present.

A good resource on this topic is available here. There have been many hypotheses over the years as to how these clouds and their effects will change in a changing climate. You can search for things like the "Iris hypothesis"--and subsequent refutation--as a good example of this still-evolving science. Climate models are still struggling to cope with correctly representing all of the feedbacks associated with clouds, which causes such high uncertainty in cloud effects in the IPCC reports.

One last thing to keep in mind is that these forcings are relative to a column with no cloud in the current climate. But what if our distributions or regimes of clouds greatly shift? If the planet warms so much that ice clouds can never exist, the relative forcing of ice clouds in that climate would then be null. So akeep in mind the point of reference you are using when thinking about the forcing of clouds.


What are these basal rip up clasts in North Dakota?

Short answer: They are clasts from adjacent hillside deposited
inmediately after the Chicxulub impact.

The log you posted represents a sudden onshore inundation event due to the impact.
The paper you provided clarifies it [1]:

Tanis site, which documents a turbulently deposited, rapidly emplaced
sediment package directly overlain by the Cretaceous–Paleogene (KPg)
boundary tonstein. The site, situated in the continental Hell Creek
Formation in southwestern North Dakota (Fig. 1), displays
inland-directed flow indicators and holds a mixture of Late Cretaceous
marine and continental biota, implying that its emplacement is related
to sudden onshore inundation surges.

Figure 1: Tanis Site, North Dakota.

Figure 2: Log of Tanis Site, North Dakota.

The unit 1 is described bellow. The contact between conglomerates and the point-bar is non gradational, and the rip-up clasts come from Hell Creek strata above the river (1C).

The base of unit 1 comprises a matrix-supported, massive coarse-sand
conglomerate, with angular pebble- to small boulder-sized rip-up
clasts derived from the underlying Hell Creek strata. As shown in Fig.
2, the massive sand (1a) at the base of unit 1 has a sharp
non gradational basal contact with the underlying point-bar surface and
vertically grades into a thin (∼3-cm) zone of plane-parallel bedding
of interlaminated sand–silt (lower 1b); climbing ripples (mid 1b);
sinuous, wavy lamination (upper 1b); low-angle cross-lamination (lower
1c); fine, discontinuous subparallel lamination (upper 1c); and nearly
structureless fine silt/mud near the top (1d). Flow-direction reverses
180° toward the east—seaward—near the top of unit 1

My guess is they were transported to the sand-bar from the hillside because of the sudden event, before the conglomerate clasts started to fall from the sky.

The whole depositional unit took place shortly, and before the iridium layer.

Because the Tanis deposit contains ejecta throughout and is also
capped by the KPg tonstein, the depositional event took place
during a narrow window of time: after impact but before deposition
of the fine-grained KPg tonstein. Given this constraint, we can
deduce that the Event Deposit was emplaced within a matter of hours
after the Chicxulub impact event.

The subsequent conglomerates are aerial deposits .The event is nicely described at the paper.

We assume a scenario in which ejecta-curtain material, launched at
about a 45° elevation angle and seen as the glassy or altered-glass
spherules at Tanis, arrived before the shocked quartz that was
launched at steep angles in a “warm fireball” produced by release of
CO2 from shocked limestone after departure of the ejecta curtain

 1    Robert A. DePalma, Jan Smit, David A. Burnham, Klaudia Kuiper, Phillip L. Manning, Anton Oleinik, Peter Larson, Florentin J. Maurrasse, Johan Vellekoop, Mark A. Richards, Loren Gurche, Walter Alvarez, (2019):
"A seismically induced onshore surge deposit at the KPg boundary, North Dakota"
Proceedings of the National Academy of Sciences Apr 2019, 201817407; DOI: 10.1073/pnas.1817407116


Gaps in locations of volcanos (Peru & Chile)

As you said, the Andean belt is divided into four segments, usually called the northern, central, southern, and austral volcanic zones (NVZ, CVZ, SVZ and AVZ, respectively; your map lacks the AVZ). This has been interpreted as a difference in the angle of subduction. Under the active zones, the subducting plate (called "slab") sinks into the mantle, releasing water, and the hydrated mantle partially melts, a process called "metasomatism". But under the gaps, the slab has a low angle ("flat slab subduction"), so it doesn't sink deep enough to trigger the melting process. There is no partial melting of the mantle under these zones.

Now, why has the slab failed to sink under these zones? This is due to the presence of submarine ridges. Between the NVZ and CVZ, there is the Nazca Ridge. Similarly, there is the Juan Fernandez ridge between the CVZ and SVZ. Those ridges are young, making the oceanic crust less dense, thus more buoyant (usually it is old, dense oceanic crust that subducts). The ridges also make the oceanic crust thicker, thus harder to subduct.

Image source; by Chiton magnificus in 2011 and placed in the public domain.

Two papers if you want to go further:

Volcanic gaps due to oblique consumption of aseismic ridges
Geodynamics of flat subduction: Seismicity and tomographic constraints from the Andean margin


Can we see lava in a divergent tectonic boundary?

No, we can't. This is because of several reasons, mostly stemming from the fact that the plates are not diverging fast enough to keep the lava hot enough before it cools down.

If we go and look on diverging plate boundaries on land, such as on Iceland or East Africa, you don't have a "line" of lava. Instead, you have individual volcanoes located along a linear trend:

source: http://volcano.oregonstate.edu/vwdocs/volc_images/africa/africa.html

You see all the volcanoes along a line in the Ethiopia and Kenya region? It's not one "line of lava", but single volcanoes along a line.

If we think about divergent boundaries underwater, where the lava comes from a much shallower depth, we may think it might be possible to see this kind of feature. The problem is that water is extremely effective in cooling down lava. Here's an example video of what happens when there is lava underwater:

https://www.youtube.com/watch?v=hmMlspNoZMs

As you can see, the lava cools in seconds. It doesn't erupt fast enough to sustain a constant liquid lava "line" under water.

This is not something that happens on Earth. But on other planets, maybe. If we think of a planet where the surface temperatures are on the hundreds of degrees Celsius (such as Venus), the cooling of the lava may be slow enough for plate tectonics (if they exist on said planet) to catch up and provide enough magma to sustain a long-lived magma lake-river on the boundary.


What would the geology and climate of a supposed landmass near the pole be like, assuming a thoroughly warmer planet?

For a very basic explanation of why poles are the way they are, note that the amount of solar radiation coming from the sun is spread over a larger area at the pole. Therefore you get less radiation per square meter. As a result it is colder.

Cold air can hold less water vapour. As such it is very dry (in terms of water mass per air volume) in cold regions. Dry air obviously can provide less precipitation. If your polar continent is warmer, you'll see more precipitation.

Large-scale weather phenomena are indeed mostly driven by Earth's rotation. As such you have somewhat more stable conditions along the poles. However, complex topography (i.e. mountains) can severely interfere with these conditions. This is the reason why the stratospheric ozone hole is much smaller in the northern hemisphere than in the southern hemisphere: There is much more mixing between differnt air regions in the north. In the troposphere this effect is even more pronounced.


How much of the underwater land masses within the arctic ocean is considered continental shelf?

Yool & Fasham in An Examination of the Continental shelf pump in an open ocean general circulation model Global Biogeochemical Cycles Volume 15, Issue 4, pages 831–844, divide the continental shelves into 32 named regions (see Fig. 2), and give areas for each (see table 1).

The regions that are completely in the arctic ocean are:

Russian arctic shelf 1,503,000 sq. km.

Siberian arctic shelf 1,825,000 sq. km.

North American arctic shelf 498,000 sq. km.

There are three other regions that are partially in the arctic ocean,

Iceland and Greenland shelf, North Sea shelf, and Berring Sea shelf, but looking at Fig. 2 and table 1 these seem like small contributors.

Roughly 4 million sq. km total.


Evidence of a seismic trigger of the Storegga Slide ~8.2ka

Scandinavia experienced a lot of earthquakes due to post glacioisostatic rebound 10 - 7 ka. The most likely trigger for the Storegga Slide was a strong earthquake or a series of earthquakes. However, large sediment input from glaciation rather than earthquakes are the causes of the unstable slope. Release of overpressured gas hydrates was the driving force for the violent development of the slide.

  It is reasonable to relate the period with strong earthquakes with
  rapid  rebound  and  the  triggering  of  the  Storegga  Slide.
  Recent modelling shows that the seismic energy can induce
  ground shaking that lasts longer than previously assumed in
  the deep sedimentary Møre basin (Lindholm et al., 2005). In
  the Storegga region the isostatic deformation and reactivation  of  Late  Jurassic–Early  Creteaous  faults  because  of sediment loading on the North Sea Fan probably caused an elevated earthquake level. [...] The combined effects of excess pore pressure, exposure of ooze, relative steep slopes 10–20°
  and to the vicinity of potential  earthquake  centres  favour  an  initial  slide  in  the distal  area.

Bryn et al. (2005)

Bryn, P., et al. "The Storegga Slide complex; repeated large scale sliding in response to climatic cyclicity." Submarine mass movements and their consequences. Springer Netherlands, 2003. 215-222.
Bryn, P., et al. "Explaining the Storegga slide." Marine and Petroleum Geology 22.1 (2005): 11-19.
Lindholm, C., et al. "Probabilistic and deterministic seismic hazard results and influence of the sedimentary Møre Basin, NE Atlantic." Marine and petroleum geology 22.1 (2005): 149-160.
Berndt, C., et al. "Submarine slope-failure offshore Norway triggers rapid gas hydrate decomposition." 4th int. conf. on gas hydrates proc., Yokohama, Japan. 2002.
Bungum, H., Lindholm, C. and J. I. Faleide. "Postglacial seismicity offshore mid-Norway with emphasis on spatio-temporal–magnitudal variations." Marine and Petroleum Geology 22.1 (2005): 137-148.


Is there any possible way that a tropical cyclone of any strength could form over land?

No, it isn't possible for cyclones, hurricanes and typhoons, which are all different names for the same thing, to form over land. Storms can form over land, but not hurricanes, which draw their power from the sun-warmed ocean and rapidly lose their strength when they hit land. The power of a typical hurricane is immense, probably in excess of 50 megatons, which was the yield of the largest hydrogen bomb ever tested (by Russia).


Which are the equations needed to calculate how much moving Earth's water with dams would change Earth's rotation speed?

You need to calculate the change in the moment of inertia of the Earth and use conservation of angular momentum. In the case of eg. a large dam, (most of) the water will ultimately come from the sea, effectively removing a thin layer of water. The contribution of the removed water to the moment of inertia depends on the distance from the rotation axis and hence on the latitude. This is a fairly simple calculation if we assume the world is all ocean. A more precise calculation would have to take into account the shapes of the oceans. You also need the moment of inertia of the earth, which depends on the density as a function of depth.

The moment of inertia of the lake is $m(R\cos L)^2$ and the moment of inertia of a spherical shell is $\frac{2}{3}mR^2$, where m is the mass of water, $R$ is the Earth's radius and $L$ is the latitude of the lake (30.82305 degrees for Three Gorges). The relative change in the moment of inertia of the earth is then
$$\frac{mR^2(\cos^2 L - \frac{2}{3})}{I}$$
(where $I$ is the Earth's moment of inertia, $8.04×10^{37}$ kg·m$^2$) or
$$1.97×10^{-11}(\cos^2 L - \frac{2}{3}) .$$
Multiplying by the number of microseconds in a day ($8.64 \times 10^{10}$) gives:
$$1.7(\cos^2 L - \frac{2}{3}) = 1.7 × 0.071 = 0.12\,\mu\text{s}$$

Why the difference from NASA's $0.06$ ? Note that the expression changes sign at  $\cos^2 L = \frac{2}{3}$ or $L ≈ 35$ degrees (fairly close to the latitude of Three Gorges). The Earth will actually speed up if the lake is at high latitudes and slow down if it is at the equator. The $\frac{2}{3}$ term comes from the "all ocean" assumption. I presume NASA took into account the shapes of the oceans and got a more accurate value for this term.


Formation of limestone without living organisms?

Oolites are limestones that are usually considered as in-organic, although they may have bits of shell/etc in them.  These form by the precipitation of calcium carbonate around particles (sand, broken shell, etc) with a process comparable to that of an oyster.

Some oolite references:

http://www.sandatlas.org/2012/09/oolite/

http://en.wikipedia.org/wiki/Oolite

Recently I saw a reference that limestones do not deposit when Fe2+ is present. Unfortunately I can't find the reference now. If this is the case, then for the Earth, limestones require the indirect presence of life. The evolution of cyanobacteria created free oxygen in the atmosphere and the dissolved in the oceans. Hence all dissolved iron was oxidised from Fe2+ (a green colour) to Fe3+ (orange colour).


For visualization purposes, if the $35,000$ tonne rock was composed of something similar to basalt, with a density of $3 g/cm^3$ (also $3 t/m^3$), it would be a sphere with a diameter of $28.1$ m, or a cube with sides of $22.7$ m.

Using a ballistic trajectory calculator, to move anything $2000$ km down range, the object needs an initial velocity of $4430$ m/s ($15,948$ km/h, or Mach $12.9$ - hyper sonic speed), assuming a projection angle of $45$ degrees to the horizon. The rock would reach height of $500$ km.

The kinetic energy of such an object would be $3.434(10)^{14}$ J, using the equation $E_k = 0.5mv^2$.

When Mount St. Helens erupted in 1980, it released $24$ megatons of thermal energy. Using a converter, this is equivalent to $1.004(10)^{17}$ J. This is 292 times the energy required to move a $35,000$ tonne rock $2000$ km.

Now, the energy released by Mount St. Helens was the overall energy released, not the energy given to one lump of rock and Mount St. Helens was not a supervolcano. So, could a supervolcano shoot a $35,000$ tonne rock $2000$ km away? Potentially, but unlikely. Energy always takes the path of least resistance so instead of moving a $35,000$ tonne rock $2000$ km away it will more likely move significantly more material that is in the form of dust or ash.


From the material presented, it appears the southern coast of the Netherlands is subject to coastal erosion which requires the importation of sand to restore the coastal profile and maintain sand dunes that ensure the integrity of the coast.

Previously, sand was imported every five years and deposited along the coast by mechanized equipment, in a series of restoration campaigns. This is a very disruptive process for natural systems and the humans along that part of the coast.

The sand motor is an artificial, sacrificial peninsular of sand that will be redistributed along the coast, continually replenishing the sand lost to erosion. The slower and continuous redistribution of sand, but natural forces will allow for a consolidation of the coastal sand dunes in a seemingly natural manner that is not disruptive like the previous replenishment campaigns conducted every five years.

The continuous slow replenishment of coastal sand, also allows flora to naturally establish itself and colonize the sand dunes. Their roots acting as a mesh to hold sand, thus reinforcing the sand dunes in a natural and non-disruptive manner.

The project is aiming to produce a more natural way to producing long lasting sand dunes to protect the integrity of the coast.


The river or the hills; which came first?

This is a kind of chicken or egg question, since there was never really a point at which there was no river flowing, or no hills to flow around.

  My question is whether the hills preexisted the course of the river or did the river in some way cause the hills to "appear".

Most of the area which you describe along the Mississippi is formed of sand, gravel and till deposited by glaciers in the previous two glaciations. Though there would have been solid bedrock beneath it all before that, complete with hills and rivers flowing across the landscape.

Rivers flow along the path of least resistance over the landscape under the influence of gravity. This means that, in general, they will take the route with the steepest downhill gradient from their source to the sea.

  Are the hills all glacial deposits which guided the course of river?

The hills formed by glacial deposits would indeed have influenced the course of river after de-glaciation occurred. Though the flowing glacier will have shaped the hills in the first place.

At the same time, the river will be eroding the material through which it flows, so it is constantly (but very slowly) carving out new formations in the landscape. Fluvial landscapes tend to produce very dendritic landscapes – that is, comprising of a dense network of channels with many small tributaries – in comparison to landscapes formed by glaciers. In this sense, the river will be causing new hills to 'appear' as it carves out new valleys and tributaries into the glacial material. Some of the smaller hills in the area may well have been formed entirely post-glacially.

Summary:

A mixture of both really. River courses are influenced by existing topography, but they also have the power to carve out new features into the landscape.

Afterthought:
If you go back far enough in Earth history, before the formation of water at the surface, there would have been some sort of topography (hills). So you could argue that ultimately the hills came first.

Sources: Bennett and Glasser (2009) Glacial Geology; Anderson and Anderson (2010) Geomorphology


Landsat 5 DN's to Top of Atmosphere reflectance

Short answer: yes.

The Radiance to Reflectance correction described in the Handbook is just physics based. Therefore, it is valid for any Earth observing satellite. However, the mean solar exo-atmospheric irradiances (table 5-2) are specific to the wavelength bands of the ETM+ sensor. Therefore, if you want to correct other bands you would need new coefficients valid for the corresponding wavelength range.

But in the case of Landsat 5 and 7, the bands are almost identical (with very small differences on bands 4 and 7). Therefore, unless you need very high accuracy I would say that it is safe to use ETM+ coefficient (Landsat 7) to correct TM imagery (Landsat 4 and 5).

The bands for TM and ETM+ are as follows:

(taken from USGS Landsat Mission)

Note that it is not only the boundaries of the bands what matter, but also the spectral response within the band. Therefore, even for bands that seem identical, the coefficients of exo-atmospheric irradiances can present small differences.
Ideally, you should use the coefficients calculated specifically for the TM sensor, but using the ETM+ values would provide a very good approximation. At least good enough for most applications. But if you want to use the TM specific values, they are as follows:

(Taken from USGS Q&A "Where can I find the solar exoatmospheric spectral irradiances (ESUN) for the Landsat 1-5 MSS, Landsat 4-5 TM, and Landsat 7 ETM+ sensors?")


Analytical solution for seismic wavefield in MATLAB

So, I know this question was asked a long time ago. But in the spirit of Stack Exchange, I will post my answer for future users perhaps.

The Greens functions (i.e., analytical solutions)

The first thing to be aware of are the various solutions to the wave equations change for the (1) source type and (2) the dimension.

The source type

Assuming acoustic waves in a homogeneous domain, that means you are either solving:
$$ \frac{\partial^2 p(x,t)}{\partial t^2} = c^2(x)\left(\nabla^2 p(x,t) +f(x,t) \right)  , \tag{1}$$
(where $p$ is pressure, $c$ the compressional velocity and $f$ the source function), or you are solving:
$$ \left\{ \begin{array}{rl} \frac{\partial p(x,t)}{\partial t} & =  -c^2(x)\bigg( \nabla\cdot v(x,t) + g(x,t) \bigg), \\ \frac{\partial v(x,t)}{\partial t} & = -\nabla p(x,t). \end{array} \right. \tag{2} $$
The difference between (1) and (2) is a time differentiation:
$$ f(x,t) = \frac{\partial}{\partial t}g(x,t). $$
This is an important difference in source functions!

The Greens function equation

It is standard to restate equation (1) in the following form:
$$ \left( \frac{1}{c^2(x)}\frac{\partial^2}{\partial t^2} - \nabla^2 \right)p(x,t) = f(x,t). \tag{3a}$$
Transforming this equation to the frequency domain, for which $\partial^2/\partial t^2 \to -\omega^2$, and where $\omega^2/c^2=k^2$ we obtain:
$$ \left( -k^2 - \nabla^2 \right)p(x,\omega) = f(x,\omega), \tag{3b}$$
or
$$ \left( k^2 + \nabla^2 \right)p(x,\omega) = -f(x,\omega), \tag{3c}$$
We can consult, e.g., https://www3.nd.edu/~atassi/Teaching/AME%2060633/Notes/greens.pdf to find the Greens functions (for which $f(x,\omega)=\delta(x-x_s)$ with $x_s$ the source location).

The Greens functions

I'll just copy the results. For equations of type (1) we have the Green's functions $G$:
$$
\begin{array}{lrl}
\text{1-D:} & G & = −\frac{i}{2k}e^{−ik\lvert x−x_s \rvert}, \\
\text{2-D:} & G & = −\frac{i}{4}H_0^{(2)}(k \lvert x−x_s \rvert),\\
\text{3-D:} & G & = \frac{1}{4\pi}\frac{e^{−ik\lvert x−x_s \rvert} }{\lvert x−x_s \rvert}.
\end{array}
$$
Indeed, $H_0^{(2)}$ is the Hankel function, in MATLAB we simply write that with besselh(0,2, k*r).

The MATLAB implentation

I made the following changes w.r.t. your code:

The frequency vector can be defined from $f_1\in(0,\frac{1}{\Delta t})$ rather than how you did it, which is $f_2\in(-\frac{1}{2\Delta t},\frac{1}{2\Delta t})$. In this way, the Hankel function only receives positive frequencies. Moreover, it is exactly the order in which the FFT produces its output. I thus also removed the fftshift operations.
I changed the Green's function to the 2-D case, i.e., I changed const=-1i*pi to const=-1i/4.
I changed the nfft, to just using the FFT of the size of the wavelet or time vector. This made it easier to obtain results of similar amplitudes... Also, I don't divide the source function by nfft, to make the results relatively independent of the chosen dt.

Thus, the final code, having made only small changes compared to yours, becomes:

clc;    clear all;

%% Parameter Setting
vel=2000;   % velocity of medium
r=1000;     % distance at which wavefield will be observed
% the final wavelet should appear at time, t=r/vel=0.5sec

T=1;        % Total time
dt=.0025;   % time step
f0=25;      % central freq

%% Create Source Wavelet
N = round(T/dt);        % No of samples
t0 = 5/(sqrt(2)*pi*f0);     % Zero time shift
t = dt*(0:N-1);             % time vector
tau = t-t0+1*dt;     % time vector shifted by t0
src = (1 -2* tau.*tau * f0^2 * pi^2).*exp(-tau.^2 * pi^2 * f0^2);  % source wavelet

%%FT of signal
fmax=1/dt; % max frequency
freq= linspace(0,fmax,N);    % Freq vector:   0 <= f <= Fmax
sw=fft(src);      % fourier transform of wavelet, S(w)

%% 2-D Greens Function
w=2*pi*freq;
const = -1i/4;
H02 = besselh(0,2,w/vel*r);
H02(1)=0;
GF = const*H02;

%% Calculating the Wavefield
WF= ifft(GF.*sw);

%% Plot
% Wavelet
subplot(2,2,1);
plot(t,src);     title('\bf{Source wavelet}');
xlabel('Time(sec)');    ylabel('Amplitude ')

% Frequencies
subplot(2,2,2);
plot(freq,abs(sw));    title('\bf{Source freq spec}');
xlabel('Frequencies(Hz)');  ylabel('Amplitude ')
xlim([0 fmax/2])

% Gneens Fkt
subplot(2,2,3);
plot(freq,abs(GF));   title('\bf{Green Function}');
xlabel('Frequencies(Hz)'); ylabel('Amplitude ')
xlim([0 fmax/2])

% Wafefield
subplot(2,2,4);
hold on
plot(t,real(WF));    title('\bf{Trace}');
xlabel('Time(sec)');  ylabel('Amplitude')

Provided that the signal is sampled to the Nyquist frequency, this should give good results:


How to obtain the saturation point of a soil layer from the volumetric soil water content data?

I assume you mean sensors that measure volumetric soil water content. The answer will depend on the amount of precipitation and the permeability of the soil. Soils don't reach full saturation in some climates - especially coarse texture soils. I would say that if the soil water content reaches a maximum value that persists for a period of time after large rainfalls (giving a flat top) and ideally reaches the same maximum level during multiple wetting-drying cycles that it is reasonable to infer that is the saturation value.
Ideally you would collect undisturbed soil samples of known volume (e.g in by driving a cylinder into the soil (gently as possible) to determine the pore volume and saturated water content.
Also be aware that many soil moisture sensors give readings that are dependent on soil properties and are not linear up to 100% saturation so they may not give good values at high water contents. It is best to calibrate those types on your soils.


What exactly does it mean that Japan is the "land of the rising sun"?

Nippon means "sun origin" or "land of the rising sun". From the direction and point of view of the older, larger civilisation of the continent to the West - China - the island of Japan were in the general direction of where the sun rises, with no known lands further East beyond them.

China was a powerful cultural influence for Japan. Nihon/Nippon was a nicer, more poetic name than the Chinese name of "Wa" - which was Chinese for "Dwarf"; Nihon/Nippon ("sun origin") was used, possibly intentionally, to supplant it within Japan.

I don't know if Japanese or Chinese historically understood that Earth was a globe but suspect it was largely irrelevant to that naming.


How many BTU per cubic meter does typical paper waste yield when burned in a modern domestic fireplace

About 12 million BTU, or 3.5 MWh.

I searched for paper btu and got loads... of... hits.

Seems like 7000 BTU/lb is a decent starting point, or $1.6 \times 10^7\ \mathrm{J/kg}$. If we say a ream of letter-size paper weighs about 5 lb, then we can calculate that paper yields about $1.2 \times 10^{10}\ \mathrm{J/m^3}$ when burned — enough to heat the average US house for 15 weeks.


Does anyone have a geological map 1 / 1 000 000 or 1 / 50k of Morocco in HD?

It is not so evident if you look for the big picture (grammar school's project?), or detail and specific region.  Because even today, the geological mapping of Morocco is not complete (gouvernmental reference), the 19 already digitized geological maps about Morocco  on gallica.fr may be an interesting entry for you.  The GUI interface is more helpful for books, than for maps (selection of the page, export as .pdf / .jpeg), but there is a zoom and pan option to see some details on the maps pretty well.
E.g., a more general one by Brumnich (1936, 1:500'000) here, or one with stratigraphic / petrographic details about central Morocco by Termier (1932, 1:200'000) here.


Does higher hardness means that A cannot scratch B regardless of any other variable?

Welcome.

You're referring to the Mohs hardness scale, a qualitative scale to quickly determine, in the field, whether something scratches (carves a mark into) something else. It states nothing about the opposite direction. Of course, given enough pressure or kinetic energy the scraper can experience deformation as well, but that's not the meaning of the exercise.

One can pretty well scratch Gypsum with the finger nail and feldspar with a steel nail. You don't hammer things and do not scratch over and again or with more force than necessary. It's more like, for instance, cutting wood with a pocket knife. No molecules are counted and no microscopic traces investigated, it is just a superficial visual inspection for use in the field. Laboratory work comes later.

https://geology.com/minerals/mohs-hardness-scale.shtml

https://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness

https://www.nps.gov/articles/mohs-hardness-scale.htm

Edit: To make some sciency disport out of this, here's a work that deals with the force of a large cat's claws and muscles against the bones of its prey.

Even though the claw, being made of keratin (same as horn, hoove, nail, ...), only has a Mohs hardness of 2.5, it can do considerable damage to a bone of hardness 5. That's because of the kinetic energy induced by the sweep of a paw and the chain of muscles at whose end it sits.

The field test based on Mohs hardness is not affected by the application of kinetic energy.


What percentage of the earth's surface is covered by 2D or 3D reflection seismic data?

Perhaps an easier question would be - what percentage of the earth has discovered oil/gas fields! This data should be easier to find than the surveys themselves, and can probably give you a rough estimate.

For an idea of the publically available seismic surveys conducted around western Australia, this site (https://wapims.dmp.wa.gov.au/wapims) can show you all of their stored survey data. Not sure where you could get other data though, sorry!


Is there any way to measure the amount of radiation the earth receives from the sun?

Your understanding is half correct. Yes, we can measure the amount of radiation the Earth receives from the Sun.

Yes, it is difficult to get an extremely precise measure of how much radiation the Earth receives from the Sun in any one time interval. But there's not really much value in such extreme precision anyway.

However, it is fairly easy to measure solar irradiance at any one place (on earth, in the atmosphere or in space); as NASA and others currently do (kudos to farrenthorpe for the link). These measurements account for the changing distance to the sun, and the tilt of the earth, and to a very large extent the variable amount of radiation emitted from different parts of the sun's surface, because the Sun's diameter is tiny compared to the distance between the Earth and the Sun (just under 1%).

And having measured solar irradiance at one or more places, it is then easy to get a fairly precise estimate of how much radiation the Earth receives from the Sun in any one time interval.


How significant is organic cotton agriculture to the USA's total global ecological footprint?

The ecological footprint is the impact of a person or community on the environment, expressed as the amount of land required to sustain their use of natural resources.  A global hectare (gha) from Wikipedia:

  One global hectare represents the average productivity of all biologically productive areas (measured in hectares) on earth in a given year.

and...

  The global hectare is a useful measure of biocapacity as it can convert things like human dietary requirements into a physical area, which can show how many people a certain region on earth can sustain, assuming current technologies and agricultural methods. It can be used as a way of determining the relative carrying capacity of the earth.

and ...

  The total number of global hectares is approximately 11.3 billion, averaging about 1.8 global hectares per person (2004).

I highly suggest you read this page here:
http://www.footprintnetwork.org/en/index.php/GFN/page/frequently_asked_questions/
and here:http://www.footprintnetwork.org/en/index.php/newsletter/bv/humanity_now_demanding_1.4_earths

which explains global footprint quite nicely and puts it into perspective.

  The data show that humanity’s demand on the biosphere for providing natural resources and absorbing carbon dioxide emissions is 44 percent more than what nature can provide. This ecological overshoot means it now takes approximately 18 months for the Earth to regenerate what we use in one year. The urgent threats we are facing today - most notably climate change, but also biodiversity loss, shrinking forests, declining fisheries and freshwater stress - are symptoms of this trend.


What changes in climate pattern can be observed when obliquity is at
  the extremes?

While obliquity is easily googled, the specific effects globally aren't as easy to look up, so I'll give this one a shot.

For starters, the 41,000 year variation isn't precise.  It fluctuates some, having to do with the earth and other planets not being perfect spheres and not all orbiting in the same plane of elliptic, and the planets (Primarily Jupiter), tugging on each other.   The Moon stabilizes the Earth's obliquity somewhat, though that's often overstated.  More recent models have shown that the Earth's obliquity would be reasonably stable even without the moon and in the future, the Moon could fall into resonance that will destabilize the Earth's obliquity.  (I read that researching another question,  but don't have the article handy and that doesn't really apply to your question anyway).

The easy part to look up is that Obliquity is primarily a polar and seasonal effect.  Higher Obliquity (24.5% currently and the more extreme 30% proposed in your question) means colder winters and hotter summers in higher latitudes.  (higher latitude means both poles, just for clarity, high latitude = far from equator)

High obliquity means more extreme seasonality (hotter summers and colder winters in both hemispheres). This does not change the year-average energy reaching the Earth, but in terms of temperature the Northern hemisphere is more important because it contains more land: Land warms up faster than water and it also hosts the reflective ice-sheets that contribute to Earth's cooling. As a result, Ice ages (somewhat) coincide with cold Northern Summers.

So, the simplified answer is higher obliquity, hotter earth, lower obliquity, colder earth.

Source - Milankovich

Quote:

  The tilt is in the decreasing phase of its cycle, and will reach its
  minimum value around the year 11,800 CE ; the last maximum was reached
  in 8,700 BCE. This trend in forcing, by itself, tends to make winters
  warmer and summers colder (i.e. milder seasons), as well as cause an
  overall cooling trend.

and Source - NOAA Article

  less "tilt" means less severe seasons - cooler summers and milder
  winters. The earth wobbles in space so that its tilt changes between
  about 22 and 25 degrees on a cycle of about 41,000 years. It is the
  cool summers which are thought to allow snow and ice to last from year
  to year in high latitudes, eventually building up into massive ice
  sheets.

you asked:

  How extreme can the climate get if the obliquity oscillates between 20
  and 30 degrees?

With a 20 to 30 degree variation in tilt, figuring the same 41,000 year cycle, Ice would build up in the North as the cycle leaned towards 20 degrees and ice would melt in the North as the cycle leaned towards 30 degrees.  The "milder winter" that we might expect from a 20 degree tilt would be highly overcompensated for by the cooling effect of an ice sheet if there was an ice sheet, so, "milder at lower tilt", shouldn't be taken as strictly true but only true if there isn't an ice age coinciding with the lower tilt.

It's possible a 30 degree tilt, which would cycle upwards, 28 29, 30, 29, 28), that period of high tilt, lasting 10,000 years might be enough to melt Antarctica too, which for the most part hasn't melted in 15-25 million years or so.   Needless to say, with a tilt that high, we'd probably go through more extreme variation with the rise and fall of ice ages and rapidly changing sea level, and ice age cycles are already quite extreme in terms of sea level rise, flooding from glacial melt melt and other changes.   Anyone who was alive 12,000 - 8,000 years ago could verify that the changes were intense.  Fossil records show an increase in extinctions during periods of rapid climate change.

The last maximum tilt happened 8,700 BCE, so the moving towards the maximum coinciding quite well with the end of the last ice age and the minimum is going to happen about 11,800 CE (or 11,800 AD for anyone who went to school when I did), and that (might) coincide with the rising of the next ice age, but it's a bit more complicated than that, as we've figured out how to stop ice ages by burning lots of fossil fuels, and the other orbital factors would need to be considered as well.

That's the simplified answer anyway.  A more detailed answer would take into account the other orbital cycles (see Milankovich link above), the 100,000 year problem and the large permanent glaciers which survive the entire 41,000 year cycle, such as we currently have on Greenland and Antarctica and which affect albedo.  I might try to tie that in later, but that would get longer and at my level of understanding, a bit less certain.


Does thermal bubble initiated in WRF dissipate over time?

After initialization the model calculates forward in time ncluding all physical processes represented by your setup of WRF. This probably means that the warm air will rise and thereby trigger the supercell thunderstorm. Cape can be calculated for a parcel starting at any height. If the bubble (warm anomaly) is present at the surface, and you are interested in the so-called surface-based Cape, then I would set the temperature to the environmental temperature + the warm anomaly. Why not try out both and see what the difference is? This would give you an idea of the vertical forcing magnitude of the warm anomaly.


What is the use of HV or VH polarization in Radar?

In the case of a ground looking radar, the cross-polarized signals HV and VH generally increase with surface roughness. For example, dense vegetation is one of the more depolarizing surface types because the polarization orientation of the emitted beam is scrambled over the course of multiple scattering interactions within the canopy before returning to the detector. Smoother surfaces can be thought of as having fewer (often just one) interactions and the corresponding signals are thus reflected to the detector predominately in their initial orientation (i.e. as HH or VV).

The cross-polarized signal also increases as scatters suspended in the atmosphere become less spherical in shape. This is particularly applicable in the interpretation of meteorological radar observations where it is used to estimate raindrop size, distinguish between solid and liquid precipitation and differentiate biological scatterers (e.g. flocks of birds) from hydrometers.

For a fixed target, the return signals HV and VH will have equal intensity. This is a direct result of the principle of reciprocity.


How Old Are the Verkhoyansk Mountains in Northeastern Russia?

Depends on what exactly you are looking for.

The mountains contain material which is much older, some as old as the Permian. This material is hosted in detrital sandstones, so obviously that area was not a mountain back then.

The deformation of that area, is indeed Cretaceous:

  The early stage of deformations dated as 160 Ma, the main stage dated as from 70 to 90 Ma.

So to answer your question, the mountains formed throughout the entire Cretaceous duration, but mostly in later (younger) times.


Zeolites, odor control, and the witchcraft of sunlight

Zeolites are very similar to clays, with one key difference. The molecular structure of clays is rather compact. In contrast, the molecular structure of zeolites has tiny molecular-sized holes, and these holes are wont to connect. The result is a porous, tunnel-filled structure at the molecular level.

The resulting tunnels make zeolites very good at absorbing substances that fit very nicely in those tunnels. What those substances are depends on the zeolite. There are a large number of naturally occurring zeolites, and even larger number of manufactured zeolites. Which zeolite absorbs what substance depends very much on the nature of the holes in the zeolite. As an example, the International Space Station uses a particular kind of zeolites ("zeolite 5A") to selectively absorb carbon dioxide from the breathing atmosphere.

Zeolites would need to be discarded after becoming saturated if all they did was absorb stuff. That's not the case. It's rather easy to make zeolites relinquish the stuff they have absorbed because the absorption mechanism is rather weak. All it takes is a smallish amount of energy. Zeolites used in industrial settings are subjected to heat, noxious chemicals,or both to make them relinquish the stuff they have absorbed.

In addition to having a large number of industrial uses, zeolites have apparently become attractive to the "all natural" crowd. (I suspect the larger number of "non-natural" zeolites are verboten amongst this crowd.) Exposing zeolites to sunlight means they absorb heat and ultraviolet light. This is indeed one way to make zeolites reject whatever has been absorbed. That's not very efficient; it would be much more efficient to bake those zeolites and/or expose them to a series of caustic chemical baths. However, that wouldn't play well with the "all natural" crowd.


Are there any effects on the atmosphere comparable with ebb and flood of the oceans?

Yes, they are called atmospheric tides. They can be caused by the gravitational effect of the moon on the atmosphere (lunar tides) and also differential solar heating (thermal tides). I believe you are asking about the former which is much weaker than the latter.

You can find more about it here: https://www.springer.com/us/book/9789027726308
and https://physics.stackexchange.com/questions/201973/are-there-tides-in-the-atmosphere


How the stepness can be computed at NDBC from site with only dominant wave data and windwave data

The methodology to calculate wave steepness used by NDBC is explained in: http://www.ndbc.noaa.gov/algor.shtml

Steepness is defined as
$\xi=\frac{2\pi H_s}{gT_z^2}$ where $H_s$ is the significant wave height and $T_z$ is the average wave period.

From your dataset, you have significant wave height and average wave period so you should be fine.


Why is reverse osmosis desalination the dominant method used and not heat-based methods? Also why is brine being dumped back into the ocean?

Starting with question 2): you can use heat to evaporate the water but you need some sort of energy or thermal exchange to cool and condense it back to liquid. My understanding is that reverse osmosis (RO) is more energy efficient overall.

Question 1) Brine is only put into the oceans from system that are near the sea, which usually use seawater as a water source. The brine has an insignificant effect on the ocean salinity once it is mixed in but can have a local effect because of poor mixing and because differences in density between the brine and seawater cause it to sink to the bottom. Systems can be engineered to minimise the impact.

Inland, the brine can degrade groundwater resources if it is disposed to seep into the ground. Even in hot, dry climates, it may be difficult to completely evaporate it to dryness in lined basins so it doesn't seep in. Seepage basins are a viable option in some places where the groundwater is already to salty to use as a resource (for example where the salty water is extracted, put through an RO system and then reinjected to the same aquifer).

RO systems are designed so that the salty concentrate is removed during operation so the system doesn't need to be cleaned to remove the salt. However, impurities may still require cleaning of the membranes. There are ways to minimize the amount of cleaning needed.


Why is Vladivostock so cold, while Dalian is so warm?

Vladivostok (this is the spelling I've always seen) is located at 43º08'  N whereas Dalian lies at 38º05' N.   Five degrees make a difference.  Also, Vladivostok gets more influence from the cold Oyashio current than does Dalian.  For these reasons summers are warmer in Dalian and winters are colder in Vladivostok.


Is there a clear guideline as to what exactly constitutes a bad oil spill?

No, "bad" has no legal definition in any jurisdiction in North America. As a practical matter you can only establish regulations and enforce legal penalties, regulatory, civil or criminal by some sort of numerical, measurement based criteria.

  How much oil must be spilled?

All material economic activity has some sort of negative tradeoff, all jurisdictions have some level of permissible harm. Each jurisdiction a pipeline passes through will have some level of oil leakage or other types of environmental harm that are permitted without triggering as legal consequence for the operator. However, this does not define "bad" but merely the trigger threshold.

An international pipeline like the Enbridge pipeline that crosses countries, provinces, states etc will be subject to a different set of rules for every jurisdiction and at times combinations of jurisdictions. You'd have to check each individual jurisdiction to find the threshold for each one.

  Is it dependent on what type of oil is spilled...

Usually, yes. Since the primary harm from oil is mechanical, the viscosity of oil is the prime predictor of the harm it will cause if spilled. Crude oil varies in viscosity from a thin syrup to thick paste. The former can spread fairly far in warm weather while the later usually just piles up at the leak. The former causes more harm per unit of escaped volume than the later.

Most of the oil moved in the Enbridge is dilbit a diluted form of bitumen/asphalt from the tar sands. Bitumen/asphalt is arguably a solid so it has to be diluted with something else to make it a pumpable liquid. Depending on the viscosity chosen, the spread and mechanical risk will vary as well.

The diluent itself is going to be something volatile which could in principle constitute a greater toxicity danger than simple crude oil. Naphtha has been used in the past which is the most volatile fraction of any crude oil. Depending on the actual ratio, spilled dilbit will present a greater or lessor danger than a comparable (usually light) crude.

  and in what area,

Quite definitely.  As noted above, the oil does not spread to any significant degree without water transport. A pipeline crossing a body of water or running near one will require more rigorous construction and closer monitoring than one that does not. Oil pipelines crossing desert or arid regions cause much less harm be unit of leaked volume than do pipelines in swamps or under body of water.

  populated by what species?

Usually, but again, this varies considerably depending on jurisdiction.


The short answer is no.

Most metals do not fossilize well, they are too reactive/water soluble. Metals are usually what is doing the fossilizing, dissolved metal in groundwater is being attracted to the electrical properties of organic material and filling in or swapping places with a porous material. You might have a stain left or some of the shape as a natural casting, but not material preserved. The exception might be in amber, but it could also be really bad: amber preservation is tricky chemistry, so I am not comfortable saying yes or no. Metal objects have good short term preservation but horrid long term preservation. there are some low reactivity metals that might survive like gold, but not as fossils. But even gold is water soluble over millions of years, so even that would require some unusual conditions.


Could the 5.7 earthquake in Utah be a precursor to a larger one?

Short answer: Yes, but the odds are small.

The USGS page that you linked to also links to a forecast: "According to our forecast, over the next 1 Week there is a 1 % chance of one or more aftershocks that are larger than magnitude 5.7."

USGS also notes:

  No one can predict the exact time or place of any earthquake,
  including aftershocks. Our earthquake forecasts give us an
  understanding of the chances of having more earthquakes within a given
  time period in the affected area. We calculate this earthquake
  forecast using a statistical analysis based on past earthquakes.


The age of groundwater can vary over a large span. The moment a drop of rain enters the ground it becomes groundwater and when it reaches the groundwater table, the water starts to flow towards a lower hydrostatic level, usually towards the sea, a river or a lake. If you have a well, you'll pump up water to lower the hydrostatic level near the well, so that local groundwater will flow towards the well instead of the ocean.

The velocity of the flow depends on a number of parameters. Naturally, the distance from the recharge area, the hydrostatic pressure, that is the elevation difference over the flow, and finally but not least important, the permeability of the soil and rocks it flows through. If the ground consists of e.g. porous sand, gravel from outwash planes or very fractured rocks the water will flow fast towards a lower level, but if the ground in impermeable, eg. shale or igneous rocks without cracks, the flow will be much slower.

If you have sandy ground, and shallow groundwater table, the pesticides will reach the groundwater table in very short time (maybe days?), if the aquifer is covered by clay, it might take millennia. It also depends on the unsaturated zone and the mosture above the groundwater table.

So, unfortunately, it's impossible to answer your question(s) without more information. Shallow groundwater is typically from zero to a couple of hundred years old. Some thousand years are not uncommon and for deep aquifer (that have little hydrostatic pressure reason to flow towards an ocean). It can be millions or even billion years old.

The age of groundwater can be detected by Carbon-14 decay or by measuring known contamination, eg. CFCs, depending on the age range.

If you are worried about contamination of you your well, apart from analyse the water, I'd make some sketches of the groundwater flow, e.g. map nearby rivers (river surface = groundwater surface) and the hydrostatic level (well water surface) in your well to find out what direction the water and contamination flow. If the contamination is between you and a river, the best guess would be that the contamination flows away from you, but if you pump up alot of water, the gradient of the groundwater table might change and the contaminations flow toward your well instead of the river.


How do simulate a cloudy day for a science fair project?

My suggestion would be to use shade cloth. You can get it in different densities and different colours. I know this is not the same as clouds, but get her to think about what the differences are and how that might affect the results. If I were a judge I would be very impressed to see a section like that on the poster.


Debunking weather conspiracy with statistics - why does temperature rise then fall for last weekend in June in recent years

You are asking the wrong question. The real question is why some podunk single city festival and not other larger more costly events, like space launches, national holidays, military campaigns, hurricanes, or a million other festivals. The conspiracy theorists likely picked that festival through data dredging, which means you are not going to disprove it by looking at the same data. If you compare enough festivals you will find some in which the weather does weird things, it is the law of large numbers in action.

A festival that started in the 1970's is perfect for data dredging, there is a change in the underlying forces of weather in the 1970's. The undeniable warming trend in global climate starts around the 1970's so if you divide your data sets before and after any point around that time the data will always show a significant difference, unless you correct for that shift. Without correcting for it all you are detecting is climate change, a known factor,n anthropomorphic factor at that. So really humans are altering the weather, just not in the way your friend thinks.


Where does the water from rain in rain forests come from?

Leaves, mostly. Photosynthesis requires carbon dioxide, and it gets it via stomata - small controllable pores in the leaf. When the stomata open, water goes out, because the air is generally drier than the interior of the leaf. Water in the leaves is drawn up from the roots, via the xylem, using the suction from the lost water in the leaves, and also acting as a capillary.

As for how much water comes from transpiration, Brustaert (2005) includes a list of estimates of global annual evapotranspiration from the land that range from 0.42-0.54 my$^{-1}$ (averaged over all 1.49×10$^8$ km$^2$), and 1.18-1.4 my$^{-1}$ for the ocean (3.61×10$^8$ km$^2$). That 6.22×10$^{13}$-7.99×10$^{13}$ tonnes of water or 62.2-79.9 petatonnes, compared to 425-505 petatonnes for the ocean.

So, for Earth, the land is something like an sixth of the total evaporation. Keep in mind that that includes desert areas. A rainforest planet would have significantly higher evaporation than that, per square meter. For example, Malhi et al. (2002) calculate evapotranspiration over the rainforest in the Amazon at 1.12 my$^{-1}$. That is much closer to ocean rates than average land rates.

Brutsaert, W., 2005. Hydrology: An Introduction, Cambridge University Press.
Malhi, Y. et al., 2002. Energy and water dynamics of a central Amazonian rain forest. Journal of Geophysical Research: Atmospheres, 107(D20), p.8061.


How do we know the speed of S-waves (shear waves) in the Earth's inner core? Has this been measured?

If waves would travel only through a medium while keeping their form (i.e., P-waves remain P-waves and S-waves remain S-waves), you would obtain something a bit like this video: https://www.youtube.com/watch?v=YctV5crEXyM .

However, standard models for wave propagation are more complicated than that. Upon hitting an interface, P-waves both reflect off and refract into the other material. And if this happens at a bit of an angle, it even generates a reflected and a refracted S-wave (if the material allows it!). Something like this image:

What you see is a P-wave that comes towards an interface between two different media (Vp=P-wave velocity, Vs=S-wave velocity, \rho=density). After hitting the interface, it creates 4 new waves! Two P-waves, two S-waves. A similar figure can be made for an S-wave hitting an interface.

So we can follow a hypothetical wave-path as follows:

There is a P-wave generated at the Earth's surface that travels down from the crust to the mantle (creating 4 new wave modes as in the figure above; we follow the transmitted P-wave that goes down),
That wavefront travels from the mantle to the outer core (which creates 3 wave modes because there is no transmitted S-wave! We follow the transmitted P-wave the goes down).
That wavefront travels from the outer core into the inner core (which creates 3 wave modes, because there is no reflected S-wave; We follow the transmitted S-wave that goes down).
The S-wave travels through the center of the Earth back up to the interface between inner core and outer core (creating 3 wave modes, because there is no transmitted S-wave; We follow the P-wave that goes up).
The P-wave travels through the outer core and hits the interface with the mantle (which creates 3 wave modes because there is no reflected S-wave; We follow the P-wave that goes up).
This P-wave further travels to the Earth's crust and surface (creating more wave-modes in the process), and is measured there.

You can see some of these effects in this nice video: https://www.youtube.com/watch?v=j7eoxizmC1I that I put in the comments also. It shows P-waves in green and S-waves in red. You can see how complicated the total wavefield becomes because every interface creates new waves...so it'll be a bit hard to see the particular wavefront I described above, but you can see the general picture.

On this snapshot you see the P-wave (in green) generating an S-wave (in red) in the inner core.

So -- S-waves can exist in the inner core even when the outer core doesn't support them (because waves modes convert, as it's called, at interfaces), and their presence can be measured at the surface. I think that answers your question mostly.

Then, of course, there is still the question of how you'd measure the speed of the S-waves in the inner core, which is rather complicated. These days, it is done by assuming some seismic model of the earth (choosing V_p, V_s, and \rho everywhere within the Earth), and modeling seismic events such as on the linked YouTube video. Then you compare real recordings against your modeled data. If there are particular misfits, you create a new model and you iterate this procedure until your model fits the recorded data 'well'.

So is the shear-wave in the inner core a measured quantity or a deduced quantity? That requires a very careful definition of those terms, so I won't answer that question! Regardless, there exists a shear-wave velocity for the inner core that describes and explains recorded data very well.