8 -- WATER VAPOR CORRECTIONS

There are two methods to correct the signal arriving at the satellite for the effects of water vapor.

1. Single-Wavelength Corrections--many instruments use only a single IR wavelength, usually 10.5 µm. Therefore, there is no independent information for estimating the influence of water vapor available from the spacecraft. In this case, climatological estimates of water vapor or regional radiosonde observations must be used.
2. Two-Wavelength Corrections--because radiation at 10.5 µm is much more sensitive to water vapor than radiation at 3.7 µm, the 10.5 µm measurements can be used to correct the 3.7 µm measurements. The difference in temperature at the two wavelengths is used to estimate the correction for the influence of water vapor.

Once the atmospheric influences are removed or corrected, the SST can be inferred from the amount of infrared radiation arriving at the satellite from the surface because hotter objects emit more energy per unit area than colder objects (Stefan-Boltzmann’s Law).