Numerical Simulation and Analysis of Mesoscale Convective Systems and Severe Storms

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Due to its large economic impact as well as importance for public safety, the study of atmospheric convective systems is a high priority topic of research. Under this award the Principal Investigator will continue research on a variety of topics associated with convective storms. Specific topics to be addressed include:--Development of a radar-based climatology focusing on the spatial and temporal distribution of convection during the growth stages of mesoscale convective systems (MCS) over the U.S. to characterize the most common patterns of development that leads to MCS formation and to understand the variability of processes governing different classes of MCSs. -- Perform sensitivity studies with an advanced mesoscale numerical model to examine the relative dominance of environmental controls versus the details of early convective forcing on MCS structure and evolution.-- Using a numerical model, investigate the effects of soil moisture amounts and its inhomogeneity on the initiation and strength of MCSs.-- Using WSR-88D Doppler radar data, examine specific derecho (localized high wind) events to determine if they are characterized by a definable mesocyclone over a stable air mass and perform numerical simulations of selected cases to determine mechanisms responsible for severe wind formation.-- Obtain further insight into processes responsible for tornado formation by simulating well -documented tornadic and null cases, and by performing further idealized simu-lations.-- Investigate the processes of hail formation in two distinctive severe storm types using simplified and complex microphysical parameterizations.-- Reexamine existing data collected in the urban environment by performing numerical sensitivity experiments for both nocturnal organized convection and afternoon locally-forced convection.Successful completion of this research will lead to improved understanding and ability to forecast several types of high impact weather including flash flooding, tornadoes, high winds and severe hail.A-i