Tropospheric Emission Spectrometer nadir spectral radiance comparisons

Accurate TES retrievals of surface and atmospheric parameters such as trace gas amounts critically depend on well-calibrated radiance spectra. On-orbit TES nadir observations were evaluated using carefully selected, nearly coincident spectral radiance measurements from Atmospheric Infrared Sounder (AIRS) on Aqua and special scanning high-resolution interferometer sounder (SHIS) underflights.

Modifications to the L1B calibration algorithms for TES version 2 data resulted in significant improvements for the TES-AIRS comparisons. The comparison of TES with SHIS (adjusted for geometric differences) show mean and standard deviation differences of less than 0.3 K at warmer brightness temperatures of 290-295 K. The TES/SHIS differences are less than 0.4 K at brightness temperatures of 265-270 K. There are larger TES/SHIS comparison differences for higher-frequency TES 1A1 filter, which has less upwelling radiance signal.