Determination of Ice Water Content in Convective Cloud using Satellitic Microwave Sounding Unit and Lighting Activity

Ice Water Content (IWC) in convective clouds plays a major role in the analysis and prediction for rainstorm deep convection, also for Earth's climate research. IWC is closely connected with the form of precipitation and lighting frequency, even vary with the intensity of convective clouds, then it is pivotal to estimate the contents of ice and water accurately. Studies indicated that the microwave brightness temperatures depend not only on the amount of ice water content but also on the vertical distribution of IWC. Comparing with visible-infrared technique, microwave observation can penetrate the clouds and give a clear view of the inner structure, especially the properties of convective clouds. The microwave radiances from the Advance Microwave Sounding Unit (AMSU)-B onboard the new generation of environmental series satellitesNOAA-K/L/M, can used to analyze the parameters of convective cloud systems at frequencies from 89 to 220 GHz. The brightness temperatures of the three channels of AMSU-B near to the water vapor absorption line centered at 183.3GHz, have high sensitivity to frozen hydrometeors in precipitating clouds. With the ice contents ascend, the brightness temperatures descend result from the ice scatter attenuation. Our studies can be focused on understanding the effects of the contents of ice and water on brightness temperatures. We use two parameters to express the IWC, the Ice Water Path (IWP) and the Ice Water Thickness (IWTH). IWP is the IWC in the unit column above the weighting height, and IWTH is the IWC differences between every two weighting height. In order to retrieval the IWP and get the calculated IWTH, we use the radiation transfer model (VDISORT) to simulate the effects of the IWC on the AMSU observation, then establish the order relation between the brightness temperatures and IWC. Further more, the results of simulation also confirm that the temperature weighting functions of the three water vapor channels maximize at different altitudes, for convective cloud systems, the brightness temperatures range at 183.3f 1 GHz suggested the responses mainly above the 250 hpa level, about 11 km, while the weighting height of 183.3f 3 GHz and 183.3f 7 GHz is about 8.5 km and 6.5 km,