演講公告
新聞標題： ( 2010-03-30 )
演講主題：Challenges of Tropical Cyclone Research – Targeted Observation, Data Assimilation, and Tropical Cycloen Predictability
主講人：吳俊傑教授 (台灣大學大氣科學系)
演講日期：99年4月6日(星期二) <br> 下午2:00 –3:00
演講地點：(光復校區)科學一館223室
茶會時間：當天下午1:30科學一館205室
摘要內容：
Abstract. Advances and challenges in tropical cyclone research are highlighted in this lecture. In particular, the targeted observations from DOTSTAR (Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region) in understanding and improving the tropical cyclone predictability is demonstrated, along with the progress of the field program of THORPEX-PARC (T-PARC; THORPEX – Pacific Asian Regional Campaign)) in the summer of 2008. Typhoon Sinlaku (2008) is a case in point under T-PARC with the most abundant flight observations taken and with great potential to address major scientific issues ranging from structure change, targeted observations to extra-tropical transition. A new method for tropical cyclone initialization based on EnKF data assimilation and the WRF model is developed. By continuously assimilating (with update cyclone every 30 minutes) all available conventional soundings, 157 dropwindsondes and SFMR (Stepped Frequency Microwave Radiometer) data from 9 T-PARC flight missions during Sinlaku from September 9 to 13, a unique high-spatial/temporal-resolution and model/observation-consistent dataset is constructed for Sinlaku during the 5-day window. Simulations of Sinlaku starting at different initial time are further investigated to assess the impact of the data. It is striking that some of the simulations are able to capture the secondary eyewall cycle, while the others starting the simulation earlier with fewer data assimilated are not. This provides a unique opportunity to study the dynamical processes of the concentric eyewall formation in Sinlaku. In particular, the BSA (β-skirt axisymmetrization) formation hypothesis is examined. Not only the axisymmetric components but also asymmetric features of the potential voritcity gradient (β-skirt) and filamentation time scale are evaluated, thus providing new insight into the physics of the eyewall evolution and tropical cyclone intensity change.
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