Precipitation changes within dynamical regimes in a perturbed climate
Tropical precipitation and the character of its adjustment in response to climate warming have been examined in an ensemble of climate models. Partitioning the 500 hPa pressure velocity, ω, into four basic dynamical regimes reveals that areas which exhibit a reversal of ω from descent to ascent make a disproportionately large contribution to the total precipitation change. The four regimes’ occurrences are remarkably consistent across the ten models considered but the inter-model spread of some of the precipitation changes is very large. This large variation is, however, primarily due to two of the models, IPSL and CCSM3. A further separation into ‘dynamic’ and ‘thermodynamic’ changes confirms that the inter-model spread in precipitation is related to variations in the dynamical responses of the models. The reliability of models for climate change studies can to some extent be gauged by their ability to represent present day climate variability. An example, using interannual variability, is presented for the Hadley Centre model, HadGEM1. This highlights potential strengths and weaknesses of the model regarding simulation of the relationships between precipitation, surface temperature, and the large-scale circulation.