Projecting Future Changes in Extratropical Transition of Atlantic Hurricanes in Earth System Model

Due to their immense socioeconomic impacts, changes in the intensity and frequency of tropical cyclones (TCs) under a warming climate have been the research focus of many scientists in recent years. However, less research has been done on the changes in patterns of extratropical transition (ET). Understanding changes in ET in the future is important due to the concentration of major coastal metropolitan centers at latitudes where TCs traditionally lose tropical characteristics and undergo ET.

In this presentation, we examine cyclone phase space diagnostics to assess the climatology of North Atlantic TCs that undergo ET. We use a three-member historical ensemble using a 25km variable-resolution version of the Community Atmosphere Model version 5 (CAM5). Each simulation is 30 years in length, allowing us to evaluate 90 years. Cyclone phase diagrams provide objective criteria to track and quantify the process of ET. We contrast the historical simulation to two future climate scenarios following Representative Concentration Pathways RCP4.5 and RCP8.5, representing “middle-of-the-road” and “worst-case” scenarios for the 21^stCentury respectively. We examine changes in the distribution of storms from a phase space perspective, as well as analyze the changes in the spatial and temporal patterns of ET climatologically.