Effect of antenna pattern correction on AMSU-B radiances

A procedure for making antenna pattern corrections to antenna temperatures of the advanced microwave sounding unit-B, AMSU-B, is implemented. Antenna efficiencies, fractions of total power over three different solid-angle regions subtended at the satellite by the earth (plus atmosphere below 20km), cold space, and the satellite platform, are input. The results allow an improved estimate of AMSU-B brightness temperatures.

The difference between the predicted radiance and the radiance for each channel in each viewing region gives a correction factor that must be included in the calculation of the viewing region radiance for the radiometric calibration to avoid a consistent bias in the radiometric gain. Using the antenna pattern data and a profile of atmospheric brightness temperature, a set of antenna pattern corrections was simulated for each channel. The sensitivity of AMSU-B brightness temperatures to the assumed Earth temperature is investigated. The impact of the the revised AMSU-B brightness temperatures on a moisture profiling retrieval is shown.