气候变化领域集成服务门户(CCPortal): Constraining the Twomey effect from satellite observations: Issues and perspectives

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DOI	10.5194/acp-20-15079-2020
	Constraining the Twomey effect from satellite observations: Issues and perspectives
	Quaas J.; Arola A.; Cairns B.; Christensen M.; Deneke H.; Ekman A.M.L.; Feingold G.; Fridlind A.; Gryspeerdt E.; Hasekamp O.; Li Z.; Lipponen A.; Mülmenstädt J.; Nenes A.; Penner J.E.; Rosenfeld D.; Schrödner R.; Sinclair K.; Sourdeval O.; Stier P.; Tesche M.; Van Diedenhoven B.; Wendisch M.
发表日期	2020
ISSN	1680-7316
起始页码	15079
结束页码	15099
卷号	20 期号:23
英文摘要	The Twomey effect describes the radiative forcing associated with a change in cloud albedo due to an increase in anthropogenic aerosol emissions. It is driven by the perturbation in cloud droplet number concentration (1Nd; ant) in liquid-water clouds and is currently understood to exert a cooling effect on climate. The Twomey effect is the key driver in the effective radiative forcing due to aerosol cloud interactions, but rapid adjustments also contribute. These adjustments are essentially the responses of cloud fraction and liquid water path to 1Nd; ant and thus scale approximately with it. While the fundamental physics of the influence of added aerosol particles on the droplet concentration (Nd) is well described by established theory at the particle scale (micrometres), how this relationship is expressed at the large-scale (hundreds of kilometres) perturbation, 1Nd; ant, remains uncertain. The discrepancy between process understanding at particle scale and insufficient quantification at the climate-relevant large scale is caused by co-variability of aerosol particles and updraught velocity and by droplet sink processes. These operate at scales on the order of tens of me-Tres at which only localised observations are available and at which no approach yet exists to quantify the anthropogenic perturbation. Different atmospheric models suggest diverse magnitudes of the Twomey effect even when applying the same anthropogenic aerosol emission perturbation. Thus, observational data are needed to quantify and constrain the Twomey effect. At the global scale, this means satellite data. There are four key uncertainties in determining 1Nd; ant, namely the quantification of (i) the cloud-Active aerosol the cloud condensation nuclei (CCN) concentrations at or above cloud base, (ii) Nd, (iii) the statistical approach for inferring the sensitivity of Nd to aerosol particles from the satellite data and (iv) uncertainty in the anthropogenic perturbation to CCN concentrations, which is not easily accessible from observational data. This review discusses deficiencies of current approaches for the different aspects of the problem and proposes several ways forward: in terms of CCN, retrievals of optical quantities such as aerosol optical depth suffer from a lack of vertical resolution, size and hygroscopicity information, non-direct relation to the concentration of aerosols, difficulty to quantify it within or below clouds, and the problem of insufficient sensitivity at low concentrations, in addition to retrieval errors. A future path forward can include utilising co-located polarimeter and lidar instruments, ideally including high-spectral-resolution lidar capability at two wavelengths to maximise vertically resolved size distribution information content. In terms of Nd, a key problem is the lack of operational retrievals of this quantity and the inaccuracy of the retrieval especially in broken-cloud regimes. As for the Nd-To-CCN sensitivity, key issues are the updraught distributions and the role of Nd sink processes, for which empirical assessments for specific cloud regimes are currently the best solutions. These considerations point to the conclusion that past studies using existing approaches have likely underestimated the true sensitivity and, thus, the radiative forcing due to the Twomey effect. © 2020 BMJ Publishing Group. All rights reserved.
英文关键词	aerosol; albedo; cloud condensation nucleus; cloud microphysics; cloud radiative forcing; concentration (composition); droplet; optical depth; satellite data
语种	英语
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/168912
作者单位	Leipzig Institute for Meteorology, Universität Leipzig, Leipzig, Germany; Finnish Meteorological Institute, Kuopio, Finland; Nasa Goddard Institute for Space Studies, New York, United States; Department of Physics, University of Oxford, Oxford, United Kingdom; Leibniz Institute for Tropospheric Research, Leipzig, Germany; Department of Meteorology and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden; Noaa Earth System Laboratories, Chemical Science Laboratory, Boulder, United States; Space and Atmospheric Physics Group, Imperial College London, United Kingdom; Sron Netherlands Institute for Space Research, Utrecht, Netherlands; Earth System Science Interdisciplinary Center and Department of Atmospheric and Oceanic Science, University of Maryland, College Park, United States; Pacific Northwest National Laboratory, Richland, United States; School of Architecture Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Institute of Chemic...
推荐引用方式 GB/T 7714	Quaas J.,Arola A.,Cairns B.,et al. Constraining the Twomey effect from satellite observations: Issues and perspectives[J],2020,20(23).
APA	Quaas J..,Arola A..,Cairns B..,Christensen M..,Deneke H..,...&Wendisch M..(2020).Constraining the Twomey effect from satellite observations: Issues and perspectives.Atmospheric Chemistry and Physics,20(23).
MLA	Quaas J.,et al."Constraining the Twomey effect from satellite observations: Issues and perspectives".Atmospheric Chemistry and Physics 20.23(2020).