Joint Seminar: Evaluating marine low-level cloud properties from VIS/NIR and microwave satellite measurement techniques – diurnal to decadal time scales

Climate models do not yet adequately parameterize the physical and dynamical processes associated with low-level marine stratiform clouds, in part because of inadequate observational records as well as insufficient knowledge of the relevant meteorological processes. These low-level clouds are particularly important, as they reflect a large amount of solar radiation back into space because they are often horizontally extensive and optically thick. However, they only reduce outgoing terrestrial radiation by a small amount because they are nearly as warm as the underlying sea surface. Studies pointed out that an 8%–12% relative increase in low-level cloud cover would be sufficient to offset the global warming induced by a doubling of CO2. A main contributor to low-level cloudiness is subtropical stratocumulus, which occurs predominantly in eastern ocean basins over relatively cold sea surface temperatures, under strong subsidence, and in a boundary layer capped by a strong temperature inversion. Stratocumulus clouds break up into shallow cumulus clouds as the trade winds advect the boundary layer over increasingly warmer SSTs, under weaker subsidence and a weaker temperature inversion.

I will be discussing the diurnal variation of these low-level clouds over the Southeast Atlantic from SEVIRI-CLAAS2 and TMI V7 satellite data. The decadal variability of the stratus/stratocumulus clouds from ISCCP and PATMOS-X and their association with the related meteorology will be presented. Annual mean global distribution of these low-level cloud properties from AMSR-E and MODIS will be revisited. The observational uncertainties in VIS/NIR and microwave technique will also be discussed.  




13:30 h


Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg


Seethala Chellappan, University of California, San Diego


Bjorn Stevens

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