A study of cloud top microphysical characteristics in High Plains thunderstorms

Satellite observations of thunderstorms have been documented since the advent of the Geostationary Operational Environmental Satellites (GOES) in 1970's. Since GOES-8, launched in 1994, the 3.9 µm channel has been available for daytime, satellite-observed radiances with both thermal and reflected solar components. It has been shown that some thunderstorm tops have enhanced solar reflectivity in the shortwave infrared portion of the spectrum, which may be due to differences in the microphysical structure at cloud top. This study will use methods developed for the GOES Surface and Insolation Program (GSIP), to estimate the cloud top effective radius and total column optical depth using GOES imager data. The goal of this study is to look at the changes in cloud top effective radius and optical depth during thunderstorm lifecycles in the High Plains of the U.S. In addition, we will compare the GSIP effective radius retrieval with an experimental effective radius retrieval for optically thick, convectively generated ice clouds, in which the scattering properties of droxtals are assumed. Several case studies will be chosen in which storms have observed diurnal changes in the 3.9 µm reflectivity and large variations in ice crystal effective radius.