Seeding Conditions of Precipitation Enhancement Revealed by Multiple Spectral Data of Satellite. II: Super-cooled Layer Clouds

On the basis of calibration of multiple spectral satellite data, parameters of cloud properties such as particle effective radius and temperature of cloud tops were retrieved from the reflectance of visible channel and brightness temperature at 3.7 μm and 11 μm wavelengths. By means of imagery compositions such as code reflectance at visible and 3.7 μm channels and a brightness temperature of 11 μm channel with primary colors of red, blue, and green (RGB), RGB composite imagery was developed to reflect the micro- and macrophysical properties of clouds. Multiple-spectral comprehensive methodology was used to analyze the microphysical properties and precipitation for super-cooled layer clouds via polar-orbit satellite data. On the basis of the assumption of precipitation enhancement and the analyzed results, the suitable criterion for rainfall enhancement for these types of clouds is summarized by the following parameters: Cloud thickness is greater than 1.5 km, and effective radius should be less than 25 μm when the temperature ranges between ?5℃ and ?15℃ and less than 15 μm when temperature is between ?15℃ and ?25℃. The classes of cloud seed ability for precipitation enhancement and various visual classes were established by combining the thresholds of the reflectance of visible channel, effective radius, and temperature. An example was given to illustrate the evolution of clouds tracked by FY2 data with higher temporal solution and the method in which the criteria were used to determine the timing and location for cloud seeding as a guide for operational precipitation enhancement.