Statistical Analysis of Warm Season Ice Cloud Properties in Mesoscale Convective Systems over Great Plains

Insufficient scientific understanding of ice cloud microphysical properties is one of the most important reasons for labeling clouds as “the largest source of uncertainty” in climate change study. Fundamental parameters in estimates of ice clouds are ice water content (IWC) profile and ice water path (IWP), defined as the vertical integral of IWC. Usually, quantitative IWC/IWP information can be retrieved from satellite (CloudSat-CALIPSO) observations (e.g., 2C-ICE product), which serve as essential global databases for verifying model parameterizations of clouds. However, these products are likely to have large uncertainties for the optically thick precipitating clouds in mesoscale convective systems (MCSs). The ice cloud properties of MCSs comprise a large portion of cloud total mass and have significant contributions to the global IWP. Moreover, the melting ice in MCSs dominates the rainfall, which results in 30-70% of warm season rainfall in the central U.S. Thus, in addition to addressing deficiencies in the treatment of MCSs ice water in models, there has been a growing need for satellite and ground-based observation datasets to better understand the ice processes within precipitating clouds in MCSs.

Tian et al. [2016] developed algorithms to retrieve MCS ice cloud microphysical properties using Next-Generation Radar (NEXRAD) reflectivity and empirical relationships from in situ measurements. The composite gridded data from scanning NEXRAD measurements can provide an x-y-z-t (4D) characterization of clouds and could be used to retrieve 4-D IWC distributions in an MCS routinely and continuously. In this study, we will provide a 3-year (2009-2011) statistical analysis of warm season (April to August) ice properties of MCSs over the Southern Great Plains (SGP) and Northern Great Plains (NGP). Statistics are calculated based on a total of 31 tracked MCSs during May 2011 over the SGP, and the results have shown that the mean IWPs are 2.43 and 1.26 kg m^-2 for the Stratiform Rain (SR) and Anvil (AC) regions of MCSs. Their mean IWCs are 0.26 and 0.15 g m^-3, respectively, and their IWCs are increased 5-6 times and twice from 14 km to 6 km.