COMPARISON OF 6.7-MU-M RADIANCES COMPUTED FROM AIRCRAFT SOUNDINGS ANDOBSERVED FROM GOES

Radiances observed by the GOES 6.7-mu m channel are compared to comput ations from simultaneous aircraft soundings of the temperature and moi sture profiles. The soundings were measured using high precision instr uments aboard the National Center for Atmospheric Research Sabreliner. An advanced line-by-line radiative transfer model is used to simulate the satellite observations. This comparison shows that the computed b rightness temperatures overestimate the observed brightness temperatur es but reproduce the full range in observed brightness temperatures. T he computed brightness temperatures are, on average, 2.6 K higher than observed. Possible sources for this bias are investigated, such as tr ansmission through a cloudy lower boundary, scattering by thin high-le vel cirrus, and water vapor continuum absorption. It is likely that a combination of uncertainties in the radiative properties of water and unaccountable ice or aerosol absorption contributes to the disparity.