The variability in the summer Arctic cloud-capped boundary layer

Michael Tjernstrom

CIRES Visiting Fellow

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Of all climate regimes, that in the central Arctic is probably the least understood, primarily because of a lack of all sorts of observations. This poses a problem when developing parameterizations for, for example, global climate models. Parameterizations build on the ensemble of observations available on a particular sub- grid scale process. If processes in a region of the Earth, like the Arctic, are different than in other regions and there is a lack of appropriate data to build parameterizations, then it is no great surprise if global models have problems in that reagion.

In this seminar aspects of boundary-layer variability that are on the sub-grid scale in most models will be discussed using data from a field experiment in the Arctic on the Swedish icebreaker Oden. The talk will focus on two aspects: the dirunal variation and mesoscale variations. In both cases there appears to be links to drizzle formation in the shallow but persistent Arctic summer stratocumulus, which then links the observed variability to peculiarities in the cloud microphysics and aerosol formation. I will argue that if the climate of the Arctic changes, so that its aerosol environment becomes more similar to that at lower latitudes, clouds may perhaps generate a negative feedback to climate warming; probably the only (or maybe one of a few) in the Arctic.

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Thursday, July 27, 2006
2:00 PM (Refreshments at 1:50 pm)
DSRC Multipurpose Room (GC402)

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