Retrieval of upper tropospheric water vapor and upper tropospheric humidity from AMSU radiances

[摘要] A regression method was developed to retrieve upper troposphericwater vapor (UTWV in kg/m²) and upper tropospheric humidity(UTH in % RH) from radiances measured by the Advanced MicrowaveSounding Unit (AMSU). In contrast to other UTH retrieval methods,UTH is defined as the average relative humidity between 500 and200hPa, not as a Jacobian weighted average, which has theadvantage that the UTH altitude does not depend on the atmosphericconditions. The method uses AMSU channels 6-10, 18, and 19, andshould achieve an accuracy of 0.48 kg/m² for UTWV and6.3% RH for UTH, according to a test against an independentsynthetic data set. This performance was confirmed for northernmid-latitudes by a comparison against radiosonde data from stationLindenberg in Germany, which yielded errors of 0.23 kg/m² forUTWV and 6.1% RH for UTH.

[学科分类] 大气科学