Global climate impacts of stochastic deep convection parameterization in the NCAR CAM5

TitleGlobal climate impacts of stochastic deep convection parameterization in the NCAR CAM5
Publication TypeJournal Article
Year of Publication2016
AuthorsWang Y., Zhang GJ
JournalJournal of Advances in Modeling Earth Systems
Volume8
Pagination1641-1656
Date Published2016/12
Type of ArticleArticle
ISBN Number1942-2466
Accession NumberWOS:000392813100007
Keywordscommunity atmosphere model; convection; eddy-diffusivity/mass-flux; ensemble; equilibrium statistics; multicloud parameterization; part i; precipitation; radiation budget; shallow; tropical
Abstract

In this study, the stochastic deep convection parameterization of Plant and Craig (PC) is implemented in the Community Atmospheric Model version 5 (CAM5) to incorporate the stochastic processes of convection into the Zhang-McFarlane (ZM) deterministic deep convective scheme. Its impacts on deep convection, shallow convection, large-scale precipitation and associated dynamic and thermodynamic fields are investigated. Results show that with the introduction of the PC stochastic parameterization, deep convection is decreased while shallow convection is enhanced. The decrease in deep convection is mainly caused by the stochastic process and the spatial averaging of input quantities for the PC scheme. More detrained liquid water associated with more shallow convection leads to significant increase in liquid water and ice water paths, which increases large-scale precipitation in tropical regions. Specific humidity, relative humidity, zonal wind in the tropics, and precipitable water are all improved. The simulation of shortwave cloud forcing (SWCF) is also improved. The PC stochastic parameterization decreases the global mean SWCF from 252.25 W/m(2) in the standard CAM5 to 248.86 W/m(2), close to 247.16 W/m(2) in observations. The improvement in SWCF over the tropics is due to decreased low cloud fraction simulated by the stochastic scheme. Sensitivity tests of tuning parameters are also performed to investigate the sensitivity of simulated climatology to uncertain parameters in the stochastic deep convection scheme.

DOI10.1002/2016ms000756
Short TitleJ. Adv. Model. Earth Syst.
Student Publication: 
No