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Shipborne observations of the radiative effect of Southern Ocean clouds
Author(s) -
Protat Alain,
Schulz Eric,
Rikus Lawrence,
Sun Zhian,
Xiao Yi,
Keywood Melita
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd026061
Subject(s) - longwave , shortwave , cloud fraction , radiative transfer , environmental science , radiative cooling , atmospheric sciences , cloud top , cloud forcing , cloud albedo , shortwave radiation , cloud computing , atmospheric radiative transfer codes , liquid water content , radiative flux , meteorology , satellite , cloud cover , radiation , geology , physics , quantum mechanics , astronomy , computer science , operating system
This study uses shipborne cloud radar and surface radiation measurements collected over the Southern Ocean to characterize the cloud frequency, cloud fraction, and cloud radiative effects on the ocean surface. These cloud and radiative properties are also used to evaluate a regional forecast model. Low‐level clouds, either alone or cooccurring with cloud layers aloft, are present ~ 77% of the time in this data set. These clouds either had a very low or a very high cloud fraction at 12 km horizontal resolution, with about half of the clouds characterized by a cloud fraction higher than 80%. Overall, shortwave surface cooling effect dominates longwave heating, with an estimate net radiative cooling of −22 W m −2 , resulting from a −71 W m −2 shortwave cooling and a +49 W m −2 longwave heating. A strong relationship between daily surface cloud radiative effect and daily low‐level cloud fraction is found, which, if confirmed with a larger data set, could be exploited in satellite retrievals or model parameterizations for the Southern Ocean. The regional model underestimates the frequency of low‐level clouds but largely overestimates the frequency of multilayer situations. The associated radiative errors are large and complex, including reduced surface radiative cooling due to low‐level clouds compensated by enhanced surface cooling in multilayer situations.