Shipborne observations of the radiative effect of Southern Ocean clouds

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• 作者：Alain Protat ; Eric Schulz ; Lawrence Rikus ; Zhian Sun ; Yi Xiao ; Melita Keywood
• 刊名：Journal of Geophysical Research: Atmospheres
• 出版年：2017
• 出版时间：16 January 2017
• 年：2017
• 卷：122
• 期：1
• 页码：318-328
• 全文大小：824.0KB
• ISSN：2169-8996

文摘

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.