Impact of Climate Change on the Precipitation Extremes Associated with Tropical Cyclones

Hurricane and Typhoon are the major contributors to the annual damage and economic lost due to natural disaster around the world.  How the characteristics of these high-impact weather extremes change in a warming climate have attracted considerable interests from research community.  Currently the assessment on the future projected change in tropical cyclone from modeling study concluded that the global frequency of tropical cyclones will likely either decrease or remain essentially unchanged. The projected changes in individual basins, on the other hand, are less certain. Despite the number reduction of tropical cyclones, the mean intensity and associated rainfall near cyclone center are likely to increase with anthropogenic greenhouse warming.

One key uncertainty regarding to the previous studies is that the intensity of tropical cyclone and accompanying extreme rainfall are often underestimated. In this study, the present day simulation of tropical cyclone was investigated using a 20-km mesh high-resolution atmospheric general circulation model.  Realistic rainfall distributions associated with typhoon were found for simulated tracks that resemble observed tracks.  The maximum wind speed and minimum surface pressure relationship along the typhoon tracks is also well simulated. The model projected future typhoons over the NW Pacific indicates a significant reduction in typhoon occurrence except for super typhoon (wind speed higher than 130 knots).  For the rainfall associated with typhoons, projected future change is about 30-40% within the 200km radius from storm center.  The corresponding change in precipitable water amount are typically less than 20%.  It implied that there should be considerable contribution to these extreme precipitation changes from dynamical process.