Retrieval Analysis of Atmospheric Water Vapor for K-Band Ground-Based Hyperspectral Microwave Radiometer

In this letter, we study the performance of a K-band ground-based hyperspectral microwave radiometer for the observation of atmospheric water vapor. First, a prototype of a K-band ground-based hyperspectral microwave radiometer for atmospheric sounding is proposed. This microwave radiometer is able to split the 18-26-GHz signal into 80 hyperspectral channels with identical bandwidth. Simulation studies, including the retrieval performance of water vapor and the vertical resolution of observation compared with the five-humidity-channel radiometer TP/WVP-3000 under the same conditions, are presented to assess the capability of the prototype. Simulation results show that the vertical resolution of this prototype is better than that of TP/WVP-3000 at a higher altitude, and the RMS water vapor error improves by about 10% at an altitude of 0-6 km. Moreover, by simulation, we analyze the impact of the radiometer channel number on the Shannon information gain and the RMS water vapor error of the hyperspectral microwave radiometer. At an altitude of 1.5-6 km, more information can be obtained by increasing the number of microwave spectrum channels. For water vapor profiling, the improvement of the retrieval RMS error from 10 to 800 channels at a higher altitude exceeds about 5%-10%.