Joint Seminar: Towards the parameterization of aerosol indirect effect in the large scale models?

Large Edy Simulations (LES) were used to examine how aerosol impacts on marine stratocumulus
clouds couple with the diurnal cycle of the radiative forcing. In a first step, LES
of diurnal cycles of pristine precipitating and polluted nonprecipitating marine stratocumulus
helped identifying the key mechanisms and processes which control the response of the cloud to
a change in the aerosol loading. In a second step, the ability of the mixed layer framework to
reproduce the time-evolution of a pristine and a polluted marine stratocumulus as represented
by LES was evaluated. This idealization of the stratocumulus topped boundary layer represents
a good proxy for the current difficulties of general circulation models to accurately represent
the vertical structure of such boundary layers. This exercice therefore highlighted some of the
processes that should be accurately represented in large-scale models if they are to be expected
to capture the effects of the aerosol on cloud amount. Finally, it is suggested that LES might
emphasize measurable signatures of the aerosol impacts on the cloud dynamics, and might be
used to optimize the procedures of sampling and data analysis during future field campaigns.

Date

24.02.2009

Time

15:15 h

Place

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

Speaker

Irina Sandu, ECMWF

Organizers


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