RESEARCH ON MOVEMENT AND PRECIPITATION CHARACTERISTICS OF TROPICAL CYCLONES IN COASTAL AREAS OF EAST CHINA

Tropical cyclones are amongst the most powerful and destructive meteorological systems on earth.Tropical cyclones can produce extremely powerful winds and torrential rain;they are also able to produce high waves and damaging storm surge as well as spawning tornadoes.With ongoing global warming predicted for the coming years,the duration and intensity of tropical cyclones will increase,and their influence will become more serious.Impact from tropical cyclones is one of the major natural hazards to the coastal cities in Southeast Asia.Tropical cyclones have caused enormous losses of life and economic damage in China,and the impacts of tropical cyclones could be made worse by population increases,more people living near the coast,greater wealth,and other factors.Thus,a more accurate prediction of the paths or tracks of tropical cyclones and the prediction of storm intensity is important for the disaster prevention and mitigation in China.Although understanding and predicting the physical processes when a tropical cyclone makes landfall(including precipitation) has become the focus of some major research programs,it is generally recognized that the progress in improving tropical cyclone intensity forecast and quantitative precipitation forecast has been slow.It is also difficult to make tropical cyclone quantitative precipitation forecast for a specified location.The forecasts from numerical weather models are generally on latitude/longitude grids and extra errors can be brought when these predictions are interpolated to a location not on the grids.Improving the skill of rainfall prediction from the short range(1-12 h) up to 3 days becomes a major target for the local forecasters and personnel in hazard mitigation organizations.Based on the TRMM 3B42RT 3-hour rainfall data and upper air circulation situation data from European Centre for Medium-Range Weather Forecasts(ECMWF),the tracks,intensities and the spatial distributions of precipitation of 29 tropical cyclones landfalling in coastal areas or entering the offshore areas of East China,and the effects of upper air circulation situation on them are analyzed during 2000-2009 with GIS spatial analysis method.The results indicate that upper air circulation situation has a regular influence on the moving tracks and the spatial distributions of precipitation for tropical cyclones,especially the westerly flow and the western end of the ridge of the West Pacific Subtropical High(WPSH) sever as important indicators in the forecasting of tropical cyclone track and precipitation distribution.The forces that affect tropical cyclone steering are the higher latitude westerlies,the subtropical ridge,and the beta effect caused by changes of the coriolis force within atmosphere.Accurate track predictions depend on determining the position and strength of high and low pressure areas,and predicting how those areas will migrate during the life of a tropical system.In addition,this study finds that the overall path of 0813 and 0815 tropical cyclone are extremely similar,and even both of their intensity are up to the super level.Subtropical high and middle-high latitude circulation parameters have significant impacts on tropical cyclone track,so circulation situation should be pay more attention by forecasters during the typhoon similar path analysis.