The Comparison Research Of Data Assimilation Of Typhoon Saomai During Landfall

Disasters brought by typhoon are known to be significantly great in China and what is worse, its hazard approaching us are becoming even more severe now than ever before. Those disasters caused by the typhoon usually happened to us human-beings during its landfall. Researching works upon forecasting Typhoon ( or tropical cyclone ) are insufficiently conducted in the past few decadeds due to the scaricity of observations. Accompanying the introduction of advanced spacial observation instruments together with scientific methods into meteorology, including GPS (Global Position System) and so on, access of. various unconventional observations with much higher resolution and precision become much more convenient to average people than ever before for academic research in the field of data assimilation to improve the simulated atmospheric state and further uplift the level of multi-lengh and multi-scale weather prediction.The numerical simulation of Saomai (0608) has been carried out by using the new generation mesoscale numerical Model WRF. It is proved that the researched typhoon track can be comparably successfully simulated by the WRF model while the simulated accumulated rainfall is somewhat less than that of the observation. Meanwhile, the modeled intensity of the typhoon Saomai is far lower than the practical situation, To further refine this situation, assimilation of various unconventional observations into the first guess field become even more necessary.Based on the comparably successful numerical simulation experiment, we further conducted a set of data assimilation (DA) experiments by assimilating COSMIC GPSRO (wetprf) and cloud-drift-wind data separately and then both together. Through comparing and diagnosing the outcomes from it and that of the former simulation experiment without any data assimilated, we found that the assimilations of both COSMIC GPSRO (wetprf) data and cloud-drift-wind data could produce better atmospheric initial state that is more similar to the real situation The former contributes more to the precision of modeled rainfall while the latter can better rectify the composed wind fields in the upper layers, typically at 200hPa.Abundant of works has been done in researching the orographic effect of the mountains Daiyun and Tailao located at the coastland in Fujiang and Zhejiang Province, China, during typoons' landfall. To reveal the dynamic and thermal structure of typhoon Saomai (0608) as well as its maintaining mechanism before and after landfall, a set of orographic sensitive experiments was designed by changing the terrain altitude (be lowered down to 300m, equal to the highest altitude of the land around). Through in-depth diagnosing with the outcomes of this set of orographic sensitive experiments, a series of conclusions are finally drawn. The orographic uplifting effect are proved to be quite significant upon the quantity of "Saomai" typhoon's rainstorm quantity, potential vorticiry, vertical velocity, Q vector divergence, vapor flux divergence as well as its unsymmetrical structure both dynamically and thermally.