High resolution climate modelling of the coupled ocean-atmosphere system in the tropics

This paper will outline the results from two modelling studies undertaken in CGAM to explore the sensitivity of the tropical coupled climate system to horizontal and vertical resolution.

In the first, a new high horizontal resolution coupled model, HiGEM,has been developed based on the latest Hadley Centre model, HadGEM1. A resolution of ~90km is used in the atmosphere, with an ocean resolution of 1/3 degree in both latitude and longitude globally. The performance of the model in the tropical Pacific will be described, with particular reference to the coupled behaviour of tropical instability waves and their influence on the mean climate.

In the second, a very high vertical resolution (L300) version of the French ocean model, OPA, has been coupled to the Hadley Centre atmosphere model, HadAM3, to explore the influence of the diurnal cycle on the mean and variability of the coupled system.The ocean model has 1 meter resolution near the surface and therefore captures the diurnal evolution of the ocean mixed layer.A summary of the results will be presented.