Spatiotemporal Characteristics and Large-Scale Environments of Mesoscale Convective Systems East of the Rocky Mountains

Journal Article · Fri Sep 27 00:00:00 EDT 2019 · Journal of Climate

DOI:https://doi.org/10.1175/JCLI-D-19-0137.1· OSTI ID:1567717

Feng, Zhe ^[1]; Houze, Jr., Robert A. ^[2]; Leung, L. Ruby ^[1]; Song, Fengfei ^[1]; Hardin, Joseph C. ^[1]; Wang, Jingyu ^[1]; Gustafson, Jr., William I. ^[1]; Homeyer, Cameron R. ^[3]

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1. Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington
2. Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, and Department of Atmospheric Sciences, University of Washington, Seattle, Washington
3. School of Meteorology, University of Oklahoma, Norman, Oklahoma

ABSTRACT The spatiotemporal variability and three-dimensional structures of mesoscale convective systems (MCSs) east of the U.S. Rocky Mountains and their large-scale environments are characterized across all seasons using 13 years of high-resolution radar and satellite observations. Long-lived and intense MCSs account for over 50% of warm season precipitation in the Great Plains and over 40% of cold season precipitation in the southeast. The Great Plains has the strongest MCS seasonal cycle peaking in May–June, whereas in the U.S. southeast MCSs occur year-round. Distinctly different large-scale environments across the seasons have significant impacts on the structure of MCSs. Spring and fall MCSs commonly initiate under strong baroclinic forcing and favorable thermodynamic environments. MCS genesis frequently occurs in the Great Plains near sunset, although convection is not always surface based. Spring MCSs feature both large and deep convection, with a large stratiform rain area and high volume of rainfall. In contrast, summer MCSs often initiate under weak baroclinic forcing, featuring a high pressure ridge with weak low-level convergence acting on the warm, humid air associated with the low-level jet. MCS genesis concentrates east of the Rocky Mountain Front Range and near the southeast coast in the afternoon. The strongest MCS diurnal cycle amplitude extends from the foothills of the Rocky Mountains to the Great Plains. Summer MCSs have the largest and deepest convective features, the smallest stratiform rain area, and the lowest rainfall volume. Last, winter MCSs are characterized by the strongest baroclinic forcing and the largest MCS precipitation features over the southeast. Implications of the findings for climate modeling are discussed.

• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: Climate Model Development and Validation; Water Cycle and Climate Extremes Modeling SFA
• OSTI ID: 1567717
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Vol. 32 Journal Issue: 21; ISSN 0894-8755
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English