It is proposed that aqua-planet runs of atmospheric GCMs for a set of specified idealised sea surface temperatures (SSTs) should be used as a standard test of the interaction of the physical parameterizations with each other and with the dynamics. Dynamical core tests have proved very useful in testing numerical formulation of models. Single column experiments are valuable in developing parameterizations, but at present there is nothing between them and full GCM runs in which conclusions about how the parameterizations perform and interact are difficult to make. As an example, results will be shown from an aqua-planet version of the UKMO Unified Model (version HadAM2B) run with equinoctial solar forcing and idealised SSTs. Zonally symmetric SSTs test whether the model tends to have a single equatorial convective maximum or ITCZs off the equator and for what weak equatorial SST gradients the Hadley Cells disappear. Zonally asymmetric SSTs test the relative longitudinal location and magnitude of the convective maximum, the extent to which westerly tropical zonal flows are generated and to which the extratropical storm-tracks are organised.
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