A high resolution AMIP integration using the Hadley Centre model HadAM2b

Abstract

 A high resolution (0.833° latitude by 1.25° longitude) AMIP (Atmospheric Model Intercomparison Project) integration is compared with a control integration at standard resolution (2.5° by 3.75°). Both integrations use HadAM2b, a recent version of the Hadley Centre atmospheric general circulation model. ECMWF reanalysis data for the AMIP period (1979–1988), together with other climatologies, are used to evaluate the results. An additional integration at standard resolution using the high resolution shorter time step is used to help distinguish between changes due to model resolution and those which are due to time step dependencies in the physical parametrizations. Enhanced resolution increases the vertical motion, intensifies the hydrological cycle, reduces slightly the model’s cold bias in the troposphere, shifts the westerly jets poleward and tends to increase the eddy kinetic energy and variability of the model. The high resolution simulation has less mid-latitude cloud, so altering the radiation balance. There is no evidence to suggest that increasing resolution has an impact on the model’s response to SST forcing.