Simulated Precipitation Extremes Associated with Tropical Cyclones in a Warmer Climate from Very High Resolution Climate Models

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 changes 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 accompanied extreme rainfall are often underestimated in global and regional climate model. In this study, the present day simulation and future projection of tropical cyclone (TC) was investigated using several very high-resolution (1/4° or less) atmospheric general circulation models. These models can produce more realistic intense TCs and at the same time have long enough integration to sample the climate-TC interactions without further dynamical downscaling. The spatial distribution and intensity of precipitation associated TCs at different intensity stages simulated by the model are composited and compared to the TRMM observation. Although the simulated rainfall associated with TCs is much more intense than the TRMM data concurrent along the IBTrACS TC tracks. The limited ground rainfall observation during the TC landing period suggested that TRMM satellite merged retrieval tend to underestimate the heavy precipitation associated with TCs. 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 gridded rainfall associated with typhoons (figure below), projected future occurrence change of local rainfall events exceeded 100 mm/hr will increase significantly by more than 400%. The potential risk from more frequent heavy rainfall events accompanied tropical cyclone is much larger than the mean intensity change of composite rainfall pattern or top 1000 events. Detailed analysis will illustrate the relative roles played by thermodynamic, dynamical, and other physical processes on the extreme precipitation associated with tropical cyclone in the projected future change.