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Presenter: Andrea Molod

Seminar Title: Modeling Near-Surface Sub-grid Scale Heterogeneity in GCMs

Two new GCM modeling approaches designed to capture the effects of sub-grid scale heterogeneity relevant to the simulation of near-surface processes will be presented. The first, called Extended Mosaic, models the direct influence of variations in land surface vegetation on the overlying boundary layer up to the local blending height. The other is called GridAlt, and models the effects of vertical subgrid variations by allowing the physical forcing terms to be computed on an enhanced vertical grid.

Results of GCM simulations will be presented which isolate the influence of the new techniques as implemented in the GEOS-3 GCM and in the MITgcm. The biggest impact on the simulated GCM climate of using Extended Mosaic was a change in character of a reinforcing feedback which is manifest in either a drying or a wetting regime, depending on the local surface conditions. The results of using GridAlt in a series of aquaplanet simulations show that it captures much of the effects of increased vertical resolution.

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