Topic: Multi-time scale analyses of extratropical transition of tropical cyclones in the North Atlantic
Speaker: Dr. LIU Maofeng, Princeton University
Brief introduction to the report:
Tropical cyclones (TCs) pose a strong threat to life and properties. Extratropical transition (ET), a process in which a storm gradually evolves from a tropical cyclone to an extratropical cyclone, can extend the threat into the mid-latitudes, and modify it through expansion of enhanced rainfall and wind.
At weather scales, we investigated Hurricane Irene (2011) using the high-resolution numerical simulation and a variety of observational analyses, and found that ET is a key player of the torrential rainfall from Irene.
At seasonal scales, we conducted one of the very first studies on the dynamical seasonal forecasts of transitioning TCs in the North Atlantic with a Geophysical Fluid Dynamics Laboratory (GFDL) high-resolution global climate model. The work demonstrates the skill of the model in predictions of basin wide and regional ET activity, suggesting its potential for practical applications. The work also provides a useful tool to diagnose the strength and limitation of the models’ skill in predicting TC activity, which can guide the future directions for refined forecasts.
At climate scales, we developed a general framework to explore the responses of ET activity to climate change based on the GFDL global coupled climate model. In the North Atlantic, the good skill of the model in simulating the climatology of TC and ET activity provides the basis for its use in future projections. Under the representative concentration pathway (RCP) 4.5 scenario, the projected increase of transitioning storm frequency dominates the increased exposure of the northeastern US and Western Europe to storm hazards, due to more favorable climate conditions under global warming. This has important implication for storm risk management. Our framework can be further applied to global scales.