Discussion On The Application Of WRF Model To Probable Maximum Precipitation Estimation

This paper, other from traditional PMP estimation methods, in the setting of Typhoon "Morakot" weather processes, studies the effect of Typhoon"Morakot" in China’s southeast coastal by using WRF model Typhoon displacement experiment in order to preliminarily investigate the possibility of application of WRF model to PMP estimation. The main contents of this paper is as following:Firstly, this paper uses CMA-STI Western Pacific tropical cyclone best track data and NCEP/NCAR reanalysis data to detailed diagnose and analyse Typhoon "Morakot" process from some physical quantities such as circulation, water vapor image and the stream field and vorticity field.etc. The result shows that:it is essential that Southwestern moisture from the South China Sea and the Bay of Bengal to maintain Typhoon "Morakot" precipitation process and the Typhoon "Goni" played a vapor "relay" role. Additional, it is successful using the WRF model to simulate Typhoon "Morakot" precipitation process, which shows better credibility and further can be used as the basis for subsequent sensitivity of the test.Secondly, taking Xiamen as the main study area, this paper successfully uses the data assimilation system WRF₃dvar to design Typhoon "Morakot" displaced assimilation test. In the test, the Typhoon "Morakot" moves in pre-designed5810typhoon track and lands in Quanzhou and Putian and it indicates that if Typhoon "Morakot" lands in Quanzhou and Putian, it could cause extreme day rainfall of400-500mm in Xiamen area within12hours which leads to severe impact.Lastly, specific experiment of WRF numerical simulation in which Typhoon "Goni" was filtered out was carried. The experiment showed that the Typhoon "Goni" contributed about30%in power and water vapor to the heavy rainfall of Typhoon "Morakot" in Taiwan and higher proportion in Xiamen, accounting for nearly a half. Therefore, in order to make the result of typhoon displacement experiment approximate to PMP level, Typhoon "Goni" in the South China Sea played as the more crucial amplification factor of PMP estimation in this test, and the paper suggests more further studies.