A Cyclone Climatology of the Canadian Climate Centre General Circulation Model

Abstract

The cyclone event climatology is presented for a five-year simulation by the Canadian Climate Centre general circulation model. Winter season results are given for the extratropical regions of both the Northern and the Southern hemispheres and the results are compared to an event climatology based on five years of observed data. In the Northern Hemisphere, classification of the simulated and the observed 1000 mb lows as a function of central height shows that the model has a deficiency of weak cyclones and an excess of intense cyclones while the number of cyclones of medium intensity is well simulated. The geographical distribution of the cyclone events shows that those features of the observed climatology which are thermal in nature, such as a preference for lows to form and move over relatively warm underlying surfaces, are reasonably well simulated, but the topographical features such as lee cyclogenesis and the avoidance of high terrain by lows are poorly simulated. The Southern Hemisphere also shows a deficiency of simulated cyclones although less pronounced than the Northern Hemisphere. The number of weak and strong cyclones are well simulated, and the paucity of Southern Hemisphere lows results from a deficiency of cyclones of moderate intensity. The observed climatology, which is nearly free of mountain influences, is well simulated and only a few minor problems are evident, such as a poor simulation of the winter cyclogenesis in the lee of the Andes and a tendency for model cyclones to be present over high terrain.