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Aerosol indirect effect dictated by liquid clouds
Author(s) -
Christensen Matthew W.,
Chen YiChun,
Stephens Graeme L.
Publication year - 2016
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd025245
Subject(s) - aerosol , environmental science , cloud albedo , atmospheric sciences , radiative forcing , cloud forcing , cloud top , forcing (mathematics) , liquid water content , albedo (alchemy) , moderate resolution imaging spectroradiometer , cirrus , longwave , cloud height , sea salt aerosol , cloud cover , satellite , meteorology , radiative transfer , cloud computing , geology , physics , sea salt , art , quantum mechanics , astronomy , performance art , computer science , art history , operating system
Abstract Anthropogenic aerosols have been shown to enhance the solar reflection from warm liquid clouds and mask part of the warming due to the buildup of greenhouse gases. However, very little is known about the effects of aerosol on mixed‐phase stratiform clouds as well as other cloud regimes including cumulus, altocumulus, nimbostratus, deep convection, and anvil cirrus. These additional cloud categories are ubiquitous and typically overlooked in satellite‐based assessments of the global aerosol indirect forcing. Here we provide their contribution to the aerosol indirect forcing estimate using satellite data collected from several colocated sensors in the A‐train for the period 2006–2010. Cloud type is determined according to the 2B‐CLDCLASS‐LIDAR CloudSat product, and the observations are matched to the radiative flux measurements from CERES (Clouds and the Earth's Radiant Energy System) and aerosol retrievals from MODIS (MODerate resolution Imaging Spectroradiometer). The oceanic mean aerosol indirect forcing is estimated to be −0.20 ± 0.31 W m −2 with warm low‐level cloud largely dictating the strength of the response (−0.36 ± 0.21 W m −2 ) due to their abundance and strong cloud albedo effect. Contributions from mixed‐phase low‐level cloud (0.01 ± 0.06 W m −2 ) and convective cloud (0.15 ± 0.23 W m −2 ) are positive and buffer the system due to strong aerosol‐cloud feedbacks that reduce the cloud albedo effect and/or lead to convective invigoration causing a countering positive longwave warming response. By combining all major cloud categories together, aerosol indirect forcing decreases and now contains positive values in the uncertainty estimate.