A COMBINED METHOD OF THE TRMM PRECIPITATION RADAR AND VISIBLE AND INFRARED SCANNER FOR RETRIEVAL OF CLOUD-PRECIPITATION INTERACTION

摘要

This paper presents a method for determining drizzle and clouds properties by combined use of a 95 GHz cloud profiling radar and a visible/near-IR multi-spectral radiometer from space. When clouds and drizzle coexist, both the radar and the radiometer detect the sum of scattering signals from cloud drops and drizzle. However, the radar reflectivity factor measured with a radar is mostly determined from scattering by drizzle drops. The visible/near-IR radiometer, on the other hand, is more sensitive to cloud drops than drizzle. This different sensitivity of the sensors to drop size can be used to determine the properties of drizzle and clouds, discriminatively. To examine the potential of the combined method, we have made simulations for drizzling clouds in which clouds and drizzle coexist. Results show that the method obtains an accuracy of around 10-20 percent in the drizzle reflectivity factor from a radar, cloud optical thickness and the effective radius from a radiometer when the liquid water content of drizzle is smaller than that of clouds.