A study of cloud parameters retrieval algorithm for spaceborne millimeter wavelength cloud radar

Based on data simulated by satellite radar simulator unit, two frequencies have been chosen to study the dual-frequency retrieval algorithm of cloud microwave parameters. Results suggest that:(1) 94/220 GHz is sensitive to tiny changes in drop size, which is beneficial for the retrieval of cloud radar parameters. Based on the consideration of detective ability, attenuation and manufacturing level in the industrial sector, 94/220 GHz can be chosen as the detection frequency of spaceborne cloud radar in the future; (2) the relationship between dual wavelength ratio (DWR) and median volume diameter (D₀) relies on the particle density. DWR will increase with D₀ if the particle density changes with the diameter. Otherwise, DWR will fluctuate with D₀ when the particle density is a constant. Thereby the retrieval of a constant density is very difficult; (3) backward iteration retrieval algorithm of dual frequency can be applied by 94/220 GHz and the retrieval results are consistent with the true values. Furthermore, the precision of retrieval is influenced by system noise and calibration precision. Therefore, the noise and calibration precision should be controlled under 1 dBz in order to satisfy the requirement of retrieval precision.