Title : The Extratropical Transition of Tropical Cyclones in a Warming Climate
Abstract : Tropical cyclones that undergo transformation into strong extratropical cyclones are capable of major societal impacts. How will these “extratropical transition” (ET) events change in frequency, location, intensity, and impact in a changing climate? While the question of how climate change will affect tropical cyclones has been studied extensively, much less work has been conducted to date on how climate change could affect ET. In this talk, I will present results from two different approaches to this problem, drawing on the recent work of graduate students Chunyong Jung, Allison Michaelis , and Ana Torres Vazquez. First, I will present a “pseudo global warming” case study in order to assess environmental influences on a single event , Hurricane Irene (2011). For this event, we identified greater ET intensity and an extended ET duration in a warmer climate relative to present day conditions. In order to generalize these findings, we also conducted “generic” PGW experiments with idealized ET events derived from reanalysis based composites. To avoid limitations in the PGW approach, I will also share results from a set of high resolution “tropical cyclone allowing” global model simulations. The global model results demonstrate changes in the geographical location of ET events, and illustrate that the changes are highly basin dependent. In a warmer climate, tropical cyclones retain their tropical characteristics to higher latitudes. The western North Atlantic showed the greatest geographical ET change in our global model simulations, with increases in ET in the northern portion of the Atlantic basin. Projected warming leads to stronger winds and increases in precipitation that exceed the rate of water vapor change. Results of all the experimental approaches consistently reveal the potential for greater ET intensity and impacts in a warmer climate.