气候变化领域集成服务门户(CCPortal): Stratocumulus cloud clearings: Statistics from satellites; reanalysis models; and airborne measurements

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DOI	10.5194/acp-20-4637-2020
	Stratocumulus cloud clearings: Statistics from satellites; reanalysis models; and airborne measurements
	Dadashazar H.; Crosbie E.; Majdi M.S.; Panahi M.; Moghaddam M.A.; Behrangi A.; Brunke M.; Zeng X.; Jonsson H.H.; Sorooshian A.
发表日期	2020
ISSN	1680-7316
起始页码	4637
结束页码	4665
卷号	20 期号:8
英文摘要	This study provides a detailed characterization of stratocumulus clearings off the US West Coast using remote sensing, reanalysis, and airborne in situ data. Ten years (2009 2018) of Geostationary Operational Environmental Satellite (GOES) imagery data are used to quantify the monthly frequency, growth rate of total area (GRArea), and dimensional characteristics of 306 total clearings. While there is interannual variability, the summer (winter) months experienced the most (least) clearing events, with the lowest cloud fractions being in close proximity to coastal topographical features along the central to northern coast of California, including especially just south of Cape Mendocino and Cape Blanco. From 09:00 to 18:00 (PST), the median length, width, and area of clearings increased from 680 to 1231, 193 to 443, and ~ 67000 to ~ 250000 km2, respectively. Machine learning was applied to identify the most influential factors governing the GRArea of clearings between 09:00 and 12:00 PST, which is the time frame of most rapid clearing expansion. The results from gradient-boosted regression tree (GBRT) modeling revealed that air temperature at 850 hPa (T850), specific humidity at 950 hPa (q950), sea surface temperature (SST), and anomaly in mean sea level pressure (MSLPanom) were probably most impactful in enhancing GRArea using two scoring schemes. Clearings have distinguishing features such as an enhanced Pacific high shifted more towards northern California, offshore air that is warm and dry, stronger coastal surface winds, enhanced lower-tropospheric static stability, and increased subsidence. Although clearings are associated obviously with reduced cloud fraction where they reside, the domain-averaged cloud albedo was actually slightly higher on clearing days as compared to non-clearing days. To validate speculated processes linking environmental parameters to clearing growth rates based on satellite and reanalysis data, airborne data from three case flights were examined. Measurements were compared on both sides of the clear cloudy border of clearings at multiple altitudes in the boundary layer and free troposphere, with results helping to support links suggested by this study s model simulations. More specifically, airborne data revealed the influence of the coastal low-level jet and extensive horizontal shear at cloud-relevant altitudes that promoted mixing between clear and cloudy air. Vertical profile data provide support for warm and dry air in the free troposphere, additionally promoting expansion of clearings. Airborne data revealed greater evidence of sea salt in clouds on clearing days, pointing to a possible role for, or simply the presence of, this aerosol type in clearing areas coincident with stronger coastal winds. © 2020 Copernicus GmbH. All rights reserved.
语种	英语
scopus关键词	airborne sensing; cloud classification; numerical model; remote sensing; satellite data; seasonal variation; statistical analysis; stratocumulus; California; Cape Blanco; Cape Mendocino; Oregon; United States
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/141399
作者单位	Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, United States; Science Systems and Applications, Inc., Hampton, VA, United States; NASA Langley Research Center, Hampton, VA, United States; Department of Electrical and Computer Engineering, University of Arizona, Tucson, AZ, United States; Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, United States; Naval Postgraduate School, Monterey, CA, United States
推荐引用方式 GB/T 7714	Dadashazar H.,Crosbie E.,Majdi M.S.,et al. Stratocumulus cloud clearings: Statistics from satellites; reanalysis models; and airborne measurements[J],2020,20(8).
APA	Dadashazar H..,Crosbie E..,Majdi M.S..,Panahi M..,Moghaddam M.A..,...&Sorooshian A..(2020).Stratocumulus cloud clearings: Statistics from satellites; reanalysis models; and airborne measurements.Atmospheric Chemistry and Physics,20(8).
MLA	Dadashazar H.,et al."Stratocumulus cloud clearings: Statistics from satellites; reanalysis models; and airborne measurements".Atmospheric Chemistry and Physics 20.8(2020).