Changes in Atlantic Coastal Winter Storms in the United States in Warmer Climate

Observations and climate projections indicate that Earth's global average temperature has increased and that this trend will likely continue over the coming decades in response to increasing greenhouse gas concentrations. This temperature increase will result in an increase in saturation vapor pressure as defined by the Clausius-Clapeyron relation. Given current projections that relative humidity remains nearly constant in a warmer climate, atmospheric vapor pressure is also expected to increase. The magnitude of these changes will depend on emissions and interactions with natural climate processes. It is also important to study the potential impacts warming may have on extreme weather phenomena. Whether it is threatening life and property with extreme wind and snow or providing beneficial rain to crops and drought stricken regions, extratropical cyclones are of particular interest because of the extent to which they impact society. In this study, a quasi-idealized extratropical cyclone is generated for the winter months (DJF) along the Atlantic coastal United States using compositing techniques. The cyclone composite is used as initial and lateral boundary conditions for high resolution simulations of Atlantic coastal winter storms in the United States in both present and future climate using the Weather Research and Forecasting (WRF) model. Future simulations are performed in conjunction with projections of thermodynamic changes obtained from Intergovernmental Panel on Climate Change (IPCC) General Circulation Model (GCM) ensembles. The high resolution afforded by WRF allows the diagnosis of changes in moist baroclinic processes that may be unresolved by the GCMs themselves. Dynamic and thermodynamic changes in coastal extratropical cyclone behavior are investigated including changes in surface precipitation type, storm track and intensity.