Differences between the seasonal cycles in the distribution of precipitation around cyclones in the western North Pacific and Atlantic

The seasonal cycles in the distribution of precipitation around western north Pacific and Atlantic cyclones have been examined by compositing quantitative estimates of precipitation rate relative to cyclone centers. The precipitation data sources considered include estimates produced by the European Centre for Medium Range Weather Forecasts 40-year reanalysis project, satellite based daily precipitation estimates produced by the Global Precipitation Climatology Project, and estimates derived based on observed weather reports contained in the Comprehensive Ocean Atmosphere Data Set.

Results from all three data sets suggest that for Pacific cyclones, substantially more precipitation is found in the warm sector in fall than in winter, and less precipitation is found in the cold sector in spring and summer than in winter. The seasonal cycle for Atlantic cyclones is found to be distinctly different. The distribution in precipitation around cyclones in fall and winter are not very different, while in spring and summer, less precipitation is found over much of the cyclone.

The implications for the observed seasonal cycles are discussed. The seasonal cycle for Pacific cyclones suggests that diabatic contributions to the generation of eddy available potential energy (APE) due to latent heat release should be maximal in fall, and minimal in mid-winter, while for Atlantic cyclones, maximum diabatic generation of eddy APE should occur in winter. This is suggested to be one of the factors that can contribute to the observed mid-winter minimum in the Pacific storm track, and the absence of such a minimum in the Atlantic. Possible reasons contributing to such differences between the seasonal cycles of cyclones in the two basins will be discussed.