89th American Meteorological Society Annual Meeting

Monday, 12 January 2009: 5:00 PM
HiGEM: High resolution global coupled climate modelling in the South East Pacific
Room 128AB (Phoenix Convention Center)
Len Shaffrey, NCAS-Climate, University of Reading, Reading, United Kingdom; and T. Toniazzo and J. Slingo
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.

When the horizontal resolution is increased in both the atmosphere and the ocean, there are marked improvements in the simulation of the climate of the South East Pacific. This paper will focus on two particular aspects of the simulation in HiGEM. The first of these is the improved representation of coastal upwelling and the stratocumulus decks in the South East Pacific at higher resolution. The second is the more realistic simulation of ENSO, which is largely a result of the improvement in the mean state of the Tropical Pacific due to resolving the heat transport associated with oceanic tropical instability waves.

This paper will also outline the future work with high resolution coupled climate models that is being undertaken as part of VOCALS-UK. The aim of this work is to gain further understanding of how increased resolution can improve the simulation of stratocumulus upwelling regions in global coupled climate models, and the impact that these regions have on the global climate and climate variability.

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