报告题目：A hydroclimatological perspective on landfalling hurricanes in the North Atlantic
报 告 人：Maofeng Liu
单 位：Department of Civil and Environmental Engineering, Princeton University
The extratropical transition (ET) process of hurricanes can lead to fundamental changes on hurricane structures. Particularly, many landfalling hurricanes experience ET and change from the tropical cyclone (TC) stage to the extratropical cyclone (EX) stages. The first part of this study focuses on the impact of ET on landfalling hurricane rainfall in the North Atlantic Basin. 35 U.S. landfalling hurricanes from 2002 to 2012 are analyzed. Hurricanes before and after ET show contrasting rainfall distributions. From the TC stage to the EX stage, the symmetric rainfall distribution around the storm center shifts to the front-left quadrant. The location of maximum rainfall extends from ~100 km to 200-300 km from the storm center and the rainfall coverage area substantially increases after ET, indicating larger impacting areas. For hurricanes located at the poleward side of N35o, hurricanes that experience ET produce stronger rainfall than those that do not, suggesting significant influence of ET on TC rainfall production. Further analyses show that the phasing between midlatitude trough system and hurricanes plays an important role in ET-induced rainfall pattern and amount.
Given the importance of ET, it is necessary to understand how ET changes under a warming climate. Towards this goal, we first simulate the current-day ET climatology with the GFDL climate model and compare it with observation in the North Atlantic Basin. The model shows good capabilities in capturing the ET climatology in terms of ET track patterns, ET locations and monthly ET variations. Future work involves examining changes in the ET climatology under a changing climate.