气候变化领域集成服务门户(CCPortal): Systematic errors in South Asian monsoon precipitation: Process-based diagnostics and sensitivity to entrainment in NCAR models

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DOI	10.1175/JCLI-D-18-0495.1
	Systematic errors in South Asian monsoon precipitation: Process-based diagnostics and sensitivity to entrainment in NCAR models
	Hanf F.S.; Annamalai H.
发表日期	2020
ISSN	0894-8755
起始页码	2817
结束页码	2840
卷号	33 期号:7
英文摘要	In simulations of the boreal summer Asian monsoon, generations of climate models show a persistent climatological wet bias over the tropical western Indian Ocean and a dry bias over South Asia. Here, focusing on the monsoon developing stages (May-June), process-based diagnostics are first applied to a suite of NCAR models and reanalysis products. Two primary factors are identified for the initiation and maintenance of the wet bias over the northwestern Indian Ocean (NWIO; 58-158N, 528-678E): (i) excessive tropospheric moisture and (ii) restrained horizontal advection of the 1000-800-hPa levels cold-dry air couplet that originates offshore of Somalia. Second, guided by the diagnostics, we hypothesized that insufficient dilution of convective updrafts is one possible candidate for model bias and performed a series of enhanced entrainment sensitivity experiments with NCAR CAM4. Over the NWIO, the results suggest that globally increasing the maximum entrainment rate «max leads to a drier free troposphere, arrests the vertical extension of clouds, and weakens moisture-convection and cloud-radiation feedbacks; each factor contributes to a reduced wet bias. Moreover, a higher «max leads to a reduced dry bias over South Asia through changes in the local circulation features. In CAM4, improved precipitation climatology due to increased «max suggests that insufficient dilution is one factor, but not the only one, that contributes to systematic errors. Rather, realistic representation of boundary layer processes in climate models arising out of local ocean-atmosphere interaction processes off Somalia's coast deserves attention in reducing the NWIO wet bias. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).
英文关键词	Atmospheric thermodynamics; Boundary layers; Moisture; Offshore oil well production; Systematic errors; Troposphere; Boundary layer process; Entrainment rates; Horizontal advection; Ocean-atmosphere interactions; Precipitation climatology; Tropospheric moisture; Vertical extension; Western indian oceans; Climate models; climate modeling; entrainment; error analysis; monsoon; precipitation (climatology); sensitivity analysis; Indian Ocean; Indian Ocean (West); Somalia; South Asia
语种	英语
来源期刊	Journal of Climate
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/171372
作者单位	International Pacific Research Center, University of Hawai'i, Manoa, Honolulu, HI, United States; International Pacific Research Center, Department of Oceanography, University of Hawai'i, Manoa, Honolulu, HI, United States
推荐引用方式 GB/T 7714	Hanf F.S.,Annamalai H.. Systematic errors in South Asian monsoon precipitation: Process-based diagnostics and sensitivity to entrainment in NCAR models[J],2020,33(7).
APA	Hanf F.S.,&Annamalai H..(2020).Systematic errors in South Asian monsoon precipitation: Process-based diagnostics and sensitivity to entrainment in NCAR models.Journal of Climate,33(7).
MLA	Hanf F.S.,et al."Systematic errors in South Asian monsoon precipitation: Process-based diagnostics and sensitivity to entrainment in NCAR models".Journal of Climate 33.7(2020).