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On the global character of overlap between low and high clouds
Author(s) -
Yuan Tianle,
Oreopoulos Lazaros
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50871
Subject(s) - tropopause , cloud fraction , subsidence , atmospheric sciences , climatology , geology , cloud height , environmental science , lapse rate , cloud cover , troposphere , cloud computing , structural basin , paleontology , computer science , operating system
The global character of overlap between low and high clouds is examined using active satellite sensors. Low‐cloud fraction has a strong land‐ocean contrast with oceanic values double those over land. Major low‐cloud regimes include not only the eastern ocean boundary stratocumulus and shallow cumulus but also those associated with cold air outbreaks downwind of wintertime continents and land stratus over particular geographic areas. Globally, about 30% of low clouds are overlapped by high clouds. The overlap rate exhibits strong spatial variability ranging from higher than 90% in the tropics to less than 5% in subsidence areas and is anticorrelated with subsidence rate and low‐cloud fraction. The zonal mean of vertical separation between cloud layers is never smaller than 5 km and its zonal variation closely follows that of tropopause height, implying a tight connection with tropopause dynamics. Possible impacts of cloud overlap on low clouds are discussed.