PNNL

Abstract

In this study, the Mesoscale Convective Systems (MCSs) are tracked using high-resolution radar and satellite observations over the U.S. Great Plains during April to August from 2010 to 2012. The spatiotemporal variability of MCSs precipitation is then characterized using the Stage-IV product. We found that the spatial variability and nocturnal peaks of MCS precipitation are primarily driven by the MCSs occurrence rather than the precipitation intensity. The tracked MCSs are further classified into convective core (CC), stratiform rain (SR) and anvil clouds regions. The spatial variability and diurnal cycle of precipitation in the SR regions of MCSs are not as significant as those of MCS precipitation. In the SR regions, the high-resolution, long-term ice cloud microphysical properties [ice water content (IWCs) and paths, IWPs] are provided. The IWCs generally decrease with height. Spatially, the IWCs, IWPs and precipitations are all higher over the Southern Great Plain than over the Northern Great Plain. Seasonally, those ice and precipitation properties are all higher in summer than in spring. Comparing the peak timings of MCS precipitation and IWPs from the diurnal cycles and their composite evolutions, it is found that when using the peak timing of IWPSR as a reference, the heaviest precipitation in the MCSs convective core occurs earlier, while the strongest SR precipitation occurs later. The shift of peak timings could be explained by the stratiform precipitation formation process. The IWP and precipitation relationships are different at MCS genesis, mature and decay stages. The relationships and the transition processes from ice particles to precipitation also depend on the low-level humidity.