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DOI	10.5194/acp-20-11025-2020
	Mid-level clouds are frequent above the southeast Atlantic stratocumulus clouds
	Adebiyi A.A.; Zuidema P.; Chang I.; Burton S.P.; Cairns B.
发表日期	2020
ISSN	1680-7316
起始页码	11025
结束页码	11043
卷号	20 期号:18
英文摘要	Shortwave-absorbing aerosols seasonally overlay extensive low-level stratocumulus clouds over the southeast Atlantic. While much attention has focused on the interactions between the low-level clouds and the overlying aerosols, few studies have focused on the mid-level clouds that also occur over the region. The presence of mid-level clouds over the region complicates the space-based remote-sensing retrievals of cloud properties and the evaluation of cloud radiation budgets. Here we characterize the mid-level clouds over the southeast Atlantic using lidar-and radar-based satellite cloud retrievals and observations collected in September 2016 during the ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) field campaign. We find that mid-level clouds over the southeast Atlantic are relatively common, with the majority of the clouds occurring between altitudes of 5 and 7 km and at temperatures between 0 and -20 °C. The mid-level clouds occur at the top of a moist mid-tropospheric smoke-aerosol layer, most frequently between August and October, and closer to the southern African coast than farther offshore. They occur more frequently during the night than during the day. Between July and October, approximately 64 % of the mid-level clouds had a geometric cloud thickness less than 1 km, corresponding to a cloud optical depth of less than 4. A lidar-based depolarization-backscatter relationship for September 2016 indicates that the mid-level clouds are liquid-only clouds with no evidence of the existence of ice. In addition, a polarimeter-derived cloud droplet size distribution indicates that approximately 85 % of the September 2016 mid-level clouds had an effective radius less than 7 μm, which could further discourage the ability of the clouds to glaciate. These clouds are mostly associated with synoptically modulated mid-tropospheric moisture outflow that can be linked to the detrainment from the continental-based clouds. Overall, the supercooled mid-level clouds reduce the radiative cooling rates of the underlying low-altitude cloud tops by approximately 10 K d-1, thus influencing the regional cloud radiative budget. © Author(s) 2020.
语种	英语
scopus关键词	aerosol; cloud microphysics; lidar; radar; radiation budget; remote sensing; shortwave radiation; stratocumulus; troposphere; Atlantic Ocean; Atlantic Ocean (Southeast)
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/247509
作者单位	Department of Atmospheric and Oceanic Sciences, University of California Los Angeles, Los Angeles, CA, United States; Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, FL, United States; School of Meteorology, University of Oklahoma, Norman, OK, United States; Nasa Langley Research Center, Hampton, VA 23681, United States; Nasa Goddard Institute for Space Studies, New York, NY, United States
推荐引用方式 GB/T 7714	Adebiyi A.A.,Zuidema P.,Chang I.,et al. Mid-level clouds are frequent above the southeast Atlantic stratocumulus clouds[J],2020,20(18).
APA	Adebiyi A.A.,Zuidema P.,Chang I.,Burton S.P.,&Cairns B..(2020).Mid-level clouds are frequent above the southeast Atlantic stratocumulus clouds.ATMOSPHERIC CHEMISTRY AND PHYSICS,20(18).
MLA	Adebiyi A.A.,et al."Mid-level clouds are frequent above the southeast Atlantic stratocumulus clouds".ATMOSPHERIC CHEMISTRY AND PHYSICS 20.18(2020).