Evaluating the Responses of Hurricanes to Climate Warming Using WRF and CAM Storyline Ensembles

Understanding the changes in hurricanes and their impacts with future climate warming is one of the outstanding challenges for science and society. The influences of climate change can be explored in a variety of ways. As a new approach, the storyline is a physically self-consistent unfolding of past events or plausible future events or pathways. This storyline approach has been widely used in evaluating the responses of hurricanes to potential future climate warming with commonly-used atmospheric models like the Weather Research and Forecasting (WRF) Model or the Community Atmosphere Model (CAM). However, the ensemble spread of a single model (e.g., WRF or CAM) is usually not large enough to represent the uncertainty in future climate. Using both WRF and CAM, we conduct ensemble experiments for recent hurricanes (e.g., Fiona, Sam, etc.) under present warming and the future warming conditions with global-averaged surface temperature 2 K, 3 K and 4 K warmer than preindustrial. In particular, the influences of climate warming on hurricane dynamics and risks in different scales are explored by high-resolution convection-permitting regional ensemble simulations (i.e., WRF ensemble) and relatively coarse-resolution global ensemble simulations (i.e., CAM ensemble). The combination of experiments conducted by WRF and CAM forms a double-model ensemble to better represent the uncertainty in potential climate change impacts on hurricane intensity and precipitation, and risk more broadly. Climate warming contributes to increasing the hurricane intensity and precipitation, but differences in the storm’s finer structure response to warming exist between the WRF and CAM simulations. Furthermore, we discuss aspects that need to be considered when selecting cases for storyline analysis and the implications of these selections when interpreting storm responses under climate change.