Numerical Experiments Of Rainwater Content Remote Sensing With A Combined X-band Radar-Radiometer System

The three-dimensional cloud numerical model of the Institute of Atmospheric Physics, Chinese Academy of Sciences, was used to simulate the structure and its temporal change of rainwater content and the radar reflectivity factors in a stratiform cloud occurred in Beijing on 26 June 2005. The model cloud was remotely observed by a combined X-band radar-radiometer system and a single X-band radar to retrieve rainwater content, respectively. At the same time, the attenuation correction has been applied on the radar reflectivity factors. Compare the retrieved data of the combined system and the single radar, when attenuation correction has been done or not. The effects of observation noise of combined system analysis error are also investigated.The results show that when the rainwater content was high, the retrievals by the combined system were closed to the model data as a real data, with an average relative error of 10 percent, and the accuracy of rainwater content retrieved with the combined system was obviously better than that with a single radar only. Knowing from the distributions of rainwater content in time and space, that the main errors in the combined retrieval method come from background brightness temperature and the difference of raindrop spectra. From the observations we may reveal that the attenuation correction shows well effects on both retrieved methods in extent, especially in the time of high rainwater content. The analysis experiments for observation noise show that the combined system has good capacity of parameter modulation. The effects of observation noise can be decreased by the system as lower as possible. So the retrieved dada of combined system has good quantity and well reliable.