89th American Meteorological Society Annual Meeting

Monday, 12 January 2009
HiGEM: Small scale coupling of atmosphere and tropical instability waves in a high resolution coupled climate model
Hall 5 (Phoenix Convention Center)
Len Shaffrey, NCAS-Climate, University of Reading, Reading, United Kingdom; and J. Harle
HiGEM is a national UK programme in high resolution coupled climate modelling. HiGEM is based on the latest climate configuration of the Met Office Unified Model, HadGEM1, but with the horizontal resolution increased to 1.25 x 0.83 degrees in longitude and latitude for the atmosphere, and to 1/3 x 1/3 degrees globally for the ocean. Centennial length integrations of HiGEM are being used to explore the impact of horizontal resolution on the fidelity of climate simulations.

Since HiGEM has a high resolution atmosphere coupled to a high resolution ocean, it can simulate local, coupled air-sea interactions on relatively fine scales. One of the scales that is resolved by HiGEM is the interaction of Tropical Instability Waves (TIWs) with the tropical atmosphere. Results will be presented showing that the structure of the atmospheric response to the TIWs is very similar to that seen in QuikSCAT imagery with regions of windstress divergence seen along the cross-wind SST fronts. This suggests that HiGEM is capable of simulating the coupled small-scale interactions between oceanic TIWs and the tropical atmosphere. One important question raised by these results is how the interaction between TIWs and the atmosphere in HiGEM might be parametrised in a lower resolution coupled climate models.

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