Improved Diurnal Cycle of Precipitation in E3SM With a Revised Convective Triggering Function

Journal of Advances in Modeling Earth Systems

Wuyin Lin¹  Xue Zheng²  Jean‐Christophe Golaz²  Shaocheng Xie²  Shuaiqi Tang²  Hsi‐Yen Ma²  Qi Tang²  Yi‐Chi Wang³  Guang J. Zhang⁴  Minghua Zhang⁵ 

[1] Brookhaven National Laboratory Upton NY USA;Lawrence Livermore National Laboratory Livermore CA USA;Research Center for Environmental Changes Academia Sinica Taipei Taiwan;Scripps Institution of Oceanography University of California, San Diego La Jolla CA USA;State University of New York at Stony Brook Stony Brook NY USA;

关键词: diurnal cycle of precipitation;    convective trigger;    E3SM;    convection;    climate modeling;    precipitation;   

DOI  :  10.1029/2019MS001702

来源: DOAJ

【 摘 要 】

Abstract We revise the convective triggering function in Department of Energy's Energy Exascale Earth System Model (E3SM) Atmosphere Model version 1 (EAMv1) by introducing a dynamic constraint on the initiation of convection that emulates the collective dynamical effects to prevent convection from being triggered too frequently and allowing air parcels to launch above the boundary layer to capture nocturnal elevated convection. The former is referred to as the dynamic Convective Available Potential Energy (dCAPE) trigger and the latter as the Unrestricted Launch Level (ULL) trigger. Compared to the original trigger in EAMv1 that initiates convection whenever CAPE is larger than a threshold, the revised trigger substantially improves the simulated diurnal cycle of precipitation over both midlatitude and tropical lands. The nocturnal peak of precipitation and the eastward propagation of convection downstream of the Rockies and over the adjacent Great Plains are much better captured than those in the default model. The overall impact on mean precipitation is minor with some notable improvements over the Indo‐Western Pacific, subtropical Pacific and Atlantic, and South America. In general, the dCAPE trigger helps to better capture late afternoon rainfall peak, while ULL is key to capturing nocturnal elevated convection and the eastward propagation of convection. The dCAPE trigger also primarily contributes to the considerable reduction of convective precipitation over subtropical regions and the frequency of light‐to‐moderate precipitation occurrence. However, no clear improvement is seen in intense convection and the amplitude of diurnal precipitation.

【 授权许可】

Unknown