Case Studies of the Impacts of Climate Change on Precipitation Organization in the SE US

In this study the Weather Research and Forecasting (WRF) model is used to produce case studies of the effects of climate change on precipitation organization in the Southeast U.S. Precipitation can be organized into widespread, heavy mesoscale precipitating features (MPFs) or short-lived, isolated precipitating features (IPFs). In this study precipitation organization will be analyzed using the algorithm described in Rickenbach et al. (2015) which classifies precipitation into MPFs and IPFs. In general, MPFs tend to be more common during the winter as they are linked to the large-scale forcing provided by midlatitude cyclones, while IPFs occur more often during the summer due to variations in surface heating (Rickenbach et al. 2015). Existing studies suggest that by the end of this century higher water vapor content will lead to an overall increase in precipitation, but few studies have examined changes in precipitation organization.

This study uses WRF to simulate notable wintertime and summertime precipitation events in the Southeast U.S. under present and future climate conditions. While present climate simulations will be initialized using real observed data, future climate simulations will be performed using the pseudo-global warming (PGW, Kimura and Kitoh 2007) approach. In the PGW approach the model's initial conditions are adjusted based on temperature projections from several CMIP5 general circulation model simulations.

A comparison between the present and future climate simulations for each precipitation event will reveal changes in precipitation organization due to climate change. It is hypothesized that the higher water vapor content in the future climate simulation will result in an increase in the number of IPFs, while MPFs will be more intense and longer-lasting.