Extratropical Transition and Recurvature of Tropical Cyclones in a Changing Climate

点击翻译按钮获取中文摘要

When tropical cyclones move poleward, they can produce adverse societal impacts, especially when they make landfall. While many tropical cyclones weaken as they move out of the tropics, a subset of these systems actually intensifies, and may increase in size. A recent example is Hurricane Sandy, which affected the Mid-Atlantic and Northeastern US in the fall of 2012. In recent years, there has been intensive study of how climate change would affect the frequency and intensity of tropical cyclones. However, only limited research has examined how climate change affects the important category of tropical cyclones that move out of the tropics. One expected result of climate change is warming air at upper levels in the tropics; prior research demonstrates that this upper warming limits the strengthening of tropical cyclones that would otherwise occur. However, tropical cyclones that move out of the tropics may escape this mitigating influence. Therefore, one goal of this study is to test the hypothesis that tropical cyclones exiting the tropics will show a greater intensity increase with warming than would storms that remain in the tropics. Another goal is to determine if and how warming changes the fraction of tropical cyclones that undergo the re-intensification process mentioned above. Finally, this project will also analyze changes in the locations and seasons in which tropical cyclones form. All of these goals will be accomplished using methods that are similar to what has been done in studying how tropical cyclones that remain in the tropics respond to climate change, but with a study area that extends well outside of the tropics. Highly sophisticated computer models, of the type used in weather prediction, will be used in combination with larger-scale changes obtained from climate models. Then, comparing "present day" to "future" simulations, with all else equal, allows determination of changes in the strength and frequency of tropical cyclones moving poleward into mid-latitude locations.This project addresses gaps in understanding of how climate change would influence the intensity and frequency of the subset of tropical cyclones that move out of the tropics, affecting higher-latitude locations. This category of tropical cyclones is extremely important, because it is precisely these systems, as they exit the tropics, which exert the strongest influence on the major population centers in mid-latitude locations such as the US. Given their importance, it is perhaps surprising that the response of these systems to climate change has not received more research attention to date. The project will also determine if geographical and/or seasonal changes in tropical cyclone activity will change with the climate. Owing to the highly technical nature of this project, the graduate students who work on it will gain valuable skills in scientific computing, data analysis and visualization, and in science communication. Graduate research assistants working on this project will be invited to assist in supervising undergraduate researchers, thereby gaining experience in leadership and mentoring.