Tropical Australian climate and the Australian monsoon as simulated by 23 CMIP3 models

Large-scale aspects of the Australian tropical climate are analyzed in the CMIP3 models, including means and seasonal variations of temperature, mean sea level pressure, winds, and precipitation as well as interannual variability of precipitation and its association with El Nino-Southern Oscillation (ENSO). A notable characteristic is an enormous range in model skill, but with biases in a number of variables averaging out to a surprisingly skilful representation by the ensemble area average mean. There are some significant geographical biases, with mean precipitation extending too far southward into the continental interior. The model ensemble shows seasonal reversals of low-level easterlies into westerlies and the reverse aloft, and reasonable skill in the location, orientation, and seasonal progression of the low-level monsoon "shear line." Broadscale features of winds between the equator and the continent in the Australian region are generally too weak, particularly those immediately north and northeast of the continent. Models with greater/lesser wet season precipitation over the continent have stronger/weaker low-level westerlies and more/less intense regional convection. An inverse relationship is also found between precipitation amounts and collocated continental surface temperature. Precipitation biases in models are related to differences in occurrence of convection/suppressed vertical motion, and to related precipitation amounts. Interannual variability in precipitation is too weak in the model ensemble (although model range in variability is considerable). This is not, however, the result of weak correlations with ENSO, which are found to be slightly too strong in most models.