Evidence of Atmospheric Contamination on the Measurement of the Spectral Response of theGMS-5Water Vapor Channel

The GMS-5 geostationary satellite carries a channel centered at 6.7 μm for the measurement of upper-tropospheric humidity. This channel’s spectral response shows structures that are similar to those shown by the atmospheric transmission. This note shows that these structures probably result from water vapor absorption between the calibration source and the instrument while making the response measurement. A corrected filter is proposed after normalization by the inferred atmospheric transmission. The brightness temperatures computed by a radiative transfer model using the spurious response exhibit a warm bias of about 1 K.