Mesoscale Convective Systems Simulated by a High-Resolution Global Nonhydrostatic Model over the United States and China
Abstract
Mesoscale convective systems (MCSs) contribute a large fraction of warm-season precipitation and generate hazardous weather including extreme precipitation, flooding, derechos and hail that have substantial economic and societal impacts. Uncertainties in convection parameterizations in climate models limit our understanding of MCS characteristics and reliability of future projection. We examine the MCS simulation from the global 14-km Nonhydrostatic ICosahedral Atmospheric Model (NICAM) without a cumulus parameterization against satellite observation from Global Precipitation Measurement (GPM) during 2001-2008. We focus on MCSs over the central U.S. and eastern China where they prevail from March to August. A process-oriented tracking method incorporating both cloud and precipitation criteria is used to identify and track MCSs. About 137/97 MCSs initiate in the central U.S./eastern China per warm season and most of them initiate east of high topography and in coastal regions. MCS lifetime and initiation time are well captured in NICAM but MCS number and MCS precipitation are overestimated and underestimated, respectively, over eastern China and central U.S. In both regions, NICAM simulates stronger and more concentrated precipitation and larger cold cloud system (CCS) than observations, which may be caused by classifying some synoptic systems with large CCS area as MCSs, especially in China. We also examine the large-scale environments related to MCS initiation in the U.S. Great Plains and South China where NICAM significantly underestimates MCS number in summer. Underestimation of MCS number and precipitation in the Great Plains is caused by dry biases in the model, which may be amplified by land-atmosphere interactions. For China, mean moisture in summer is well simulated and even overestimated. Deficiency in capturing the dynamic condition related to the coastal topography for triggering convection may have contributed to underestimation of MCS even in a sufficiently moist environment.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.A35S..08N