Typhoon Turned To The Preliminary Study Of The Mechanism Of Forecasting Techniques And Intensity

Being the two obstacles of typhoon forecasting, track abnormity and intensity mutation studies can provide a scientific understanding and theory support for forecast right.Empirical orthogonal function (EOF) has been applied in typhoon track forecasting. Professor Elsberry and Dr. Ford of American United Navy Graduated School have made important progress by improving the height field decomposing to vorticity field, with predict scheme of abnormal recurvature track poor. Aiming at the limitation, a predicting scheme was developed especially for singularity recurvature track. Based on the regression model which was built on vorticity field EOF expansion with stepwise discriminatory analysis, track forecast tests for Bilis and Kai-Tak affecting China in 2000 were carried and good results are obtained.Being a new mechanism of typhoon intensity variation including intensity mutation and a leading task in typhoon dynamics, Vortex Rossby Waves (referred as VRW hereafter) theory was studied in depth by Professor Montgomery and his students of Colorado University. It was noted in their studies that there exist two cases in initial vorticity field, with a single mesoscale vortex or several vortices which arrayed in one or two waves form in azimuthal. However, in real atmosphere, there exists vortex street made of two or three mesoscale vortices in typhoon eye-wall or outer region according to circulation of mesoscale structure observations. We carried numerical experiments to explore the VRW propagation features in the case of mesoscale vortex street. Results show that vortex combination appears two times during vorticity propagated inner ward, with vortex street vorticity less than that of single vortex, which is a new finding in typhoon dynamics.