Structure and Evolution of Mesoscale Convective Systems: Sensitivity to Cloud Microphysics in Convection‐Permitting Simulations Over the United States. (5th July 2018)

• Record Type: Journal Article
• Authors: Feng, Zhe; Leung, L. Ruby; Houze, Robert A.; Hagos, Samson; Hardin, Joseph; Yang, Qing; Han, Bin; Fan, Jiwen
• Is Part Of: Journal of advances in modeling earth systems. Volume 10:Number 7(2018)
• Page Start: 1470
• Page End: 1494
• Publication Date: 2018-07-05
• Subjects: mesoscale convection -- climate simulation -- storm tracking -- cloud microphysics -- precipitation -- radar observations; Geological modeling -- Periodicals; Climatology -- Periodicals; Geochemical modeling -- Periodicals; 551.5011
• DOI: 10.1029/2018MS001305
• Languages: English
• ISSNs: 1942-2466

Abstract

Abstract: Regional climate simulations over the continental United States were conducted for the 2011 warm season using the Weather Research and Forecasting model at convection‐permitting resolution (4 km) with two commonly used microphysics parameterizations (Thompson and Morrison). Sensitivities of the simulated mesoscale convective system (MCS) properties and feedbacks to large‐scale environments are systematically examined against high‐resolution geostationary satellite and 3‐D mosaic radar observations. MCS precipitation including precipitation amount, diurnal cycle, and distribution of hourly precipitation intensity are reasonably captured by the two simulations despite significant differences in their simulated MCS properties. In general, the Thompson simulation produces better agreement with observations for MCS upper level cloud shield and precipitation area, convective feature horizontal and vertical extents, and partitioning between convective and stratiform precipitation. More importantly, Thompson simulates more stratiform rainfall, which agrees better with observations and results in top‐heavier heating profiles from robust MCSs compared to Morrison. A stronger dynamical feedback to the large‐scale environment is therefore seen in Thompson, wherein an enhanced mesoscale vortex behind the MCS strengthens the synoptic‐scale trough and promotes advection of cool and dry air into the rear of the MCS region. The latter prolongs the MCS lifetimes in the Thompson relative to the Morrison simulations. Hence, different treatment of cloud microphysics not only alters MCS convective‐scale dynamics but also has significant impacts on their macrophysical properties such as lifetime and precipitation. As long‐lived MCSs produced 2–3 times the amount of rainfall compared to short‐lived ones, cloud microphysics parameterizations have profound impact in simulating extreme precipitation and the hydrologic cycle. Plain Language Summary: Massive thunderstorms over the Great Plains of the United States have become more frequent and more intense in the past decades. As Earth continues to warm, changes in the characteristics of these massive thunderstorms, which often cause flooding and severe wind damage, have major societal implications. Climate models with spatial resolution comparable to weather forecasting models can now be used to simulate the complex physics in storms and reproduce their climatological properties. However, details of how to represent the cloud microphysical processes remain uncertain, with potential implications for long‐term simulation of climate in regions of convective storms. This study examines the uncertainties associated with cloud microphysics of convective storms in the central United States by using two different microphysical representations and comparing results with a warm‐season satellite and radar observations. Microphysical processes leading to a broader and more realistic storm rainfall areas favor prolonged lifetime of the storms and thus have greater effects on the evolution of the large‐scale circulation and greater potential for storms producing floods, factors important for evaluating the effects of convective storms in a changing climate. Key Points: Warm season convection‐permitting climate simulations reproduced the observed characteristics of mesoscale convective systems Macrophysical properties of simulated mesoscale convective systems are sensitive to microphysics parameterizations Microphysics parameterizations that produce more stratiform rainfall favor longer‐lived convection through stronger dynamical feedbacks