Effects of AMSU-A cross track asymmetry of brightness temperatures on retrieval of atmospheric and surface parameters

The AMSU-A instrument on board NOAA-K provides global information on atmospheric temperature sounding, water vapor, clouds, precipitation , snow cover and sea ice concentration. However, brightness temperatures for the window channels exhibit a cross-track asymmetry which can significantly impact the retrieval of AMSU non-sounding products. As an example, the cloud liquid water along each scan line shows a pronounced asymmetry, having higher amount on one side of nadir than the other. A polynomial scheme is developed to correct the brightness temperature asymmetry along the scan line. It is shown that the quality of cloud liquid water distribution is significantly improved after the asymmetry correction is applied. The causes of the asymmetric brightness temperatures are being identified.