Tropospheric Water Vapor Profiles Retrieved from Pressure-Broadened Emission Spectra at 22 GHz

Abstract

The authors present the analysis and the evaluation of the retrieval of tropospheric water vapor profiles from pressure-broadened emission spectra at 22 GHz measured with a ground-based microwave spectroradiometer. The spectra have a bandwidth of 1 GHz with a resolution of 20 MHz and are centered at 22.235 GHz. Because of the small bandwidth, the retrieval is insensitive to clouds and measurements are possible under almost all nonprecipitating weather conditions. The retrieved profiles are evaluated with a set of 200 coincident balloon soundings with RS92 sensors. The correlation coefficient between the microwave retrievals and the RS92 measurements lies above 0.7 km, up to 8 km, and the retrievals show a wet bias compared to RS92 of 10% at 2 km, increasing to 30% at 6 km.