气候变化领域集成服务门户(CCPortal): Evolution of the Double-ITCZ Bias Through CESM2 Development

CCPortal

DOI	10.1029/2019MS001647
	Evolution of the Double-ITCZ Bias Through CESM2 Development
	Woelfle M.D.; Bretherton C.S.; Hannay C.; Neale R.
发表日期	2019
ISSN	19422466
起始页码	1873
结束页码	1893
卷号	11 期号:7
英文摘要	The structure of the east Pacific Intertropical Convergence Zone (ITCZ) as simulated in the Community Earth System Model version 2 (CESM2) is greatly improved as compared to its previous version, CESM version 1. Examination of intermediate model versions created as part of the development process for CESM2 shows the improvement in the ITCZ is well correlated with a reduction in the relative warmth of southeast Pacific sea surface temperatures (SSTs) as compared to the broader tropical mean. Cooling SST in this region enhances the zonal SST and surface pressure gradients and reduces the anomalously southward SST gradient present in boreal spring in early version of CESM2. The improvements in southeast Pacific SST are attributed to increases in low cloud cover and the associated shortwave cloud forcing over the southeast. Sensitivity tests using fixed SST simulations demonstrate the increase in cloud cover between two intermediate model versions, 119 and 125, to be driven by removal of the dependence of autoconversion and accretion rates on cloud water variance as well as the removal of a secondary condensation scheme. Both of these changes reduce drizzle rates in warm clouds increasing cloud lifetime and cloud fraction in the stratocumulus to trade cumulus transition region. The improvements in southeast Pacific shortwave cloud forcing and ITCZ climatology persist through subsequent changes to the cloud microphysics parameterizations. Despite improvements in the east Pacific ITCZ, the global mean ITCZ position and Pacific cold tongue bias strength do not exhibit a systematic improvement across the development simulations. ©2019. The Authors.
英文关键词	CESM; climate model; double ITCZ; ITCZ; model bias; Pacific rainfall
语种	英语
scopus关键词	Climate models; Clouds; Surface waters; CESM; Development process; double ITCZ; Intermediate model; Intertropical convergence zone; ITCZ; Model bias; Sea surface temperatures; Oceanography; climate modeling; cloud cover; cloud microphysics; cloud radiative forcing; cloud water; condensation; cumulus; drizzle; intertropical convergence zone; rainfall; sampling bias; sea surface temperature; shortwave radiation; temperature gradient; Pacific Ocean; Pacific Ocean (Southeast)
来源期刊	Journal of Advances in Modeling Earth Systems
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/156970
作者单位	Department of Atmospheric Sciences, University of Washington, Seattle, WA, United States; Jupiter Intelligence, Inc., San Mateo, CA, United States; Department of Applied Mathematics, University of Washington, Seattle, WA, United States; National Center for Atmospheric Research, Boulder, CO, United States
推荐引用方式 GB/T 7714	Woelfle M.D.,Bretherton C.S.,Hannay C.,et al. Evolution of the Double-ITCZ Bias Through CESM2 Development[J],2019,11(7).
APA	Woelfle M.D.,Bretherton C.S.,Hannay C.,&Neale R..(2019).Evolution of the Double-ITCZ Bias Through CESM2 Development.Journal of Advances in Modeling Earth Systems,11(7).
MLA	Woelfle M.D.,et al."Evolution of the Double-ITCZ Bias Through CESM2 Development".Journal of Advances in Modeling Earth Systems 11.7(2019).