The pyrgeometer is considered to approximate a black body. Due to this it emits long wave radiation according to: Where: - Long-wave radiation emitted by the earth surface [W/m2] - Stefan–Boltzmann constant [W/(m2·K4)] - Absolute temperature of pyrgeometer detector [kelvins] From the calculations above the incoming long wave radiation can be derived. This is usually done by rearranging the equations above to yield the so-called pyrgeometer equation by Albrecht and Cox. Where all the variables have the same meaning as before. As a result, the detected voltage and instrument temperature yield the total global long wave downward radiation. Usage Pyrgeometers are frequently used in meteorology, climatology studies. The atmospheric long-wave downward radiation is of interest for research into long term climate changes. The signals are generally detected using a data logging system, capable of taking high resolution samples in the millivolt range. See also Pyranometer Radiometer References Electromagnetic radiation meters Radiometry