Precipitation Organization in a Warmer Climate

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Monday, 5 January 2015
Mark Nissenbaum, East Carolina University, Greenville, NC; and R. Ferreira and T. M. Rickenbach

This study will investigate changes in precipitation organization in a warmer climate using the Weather Research and Forecasting (WRF) model. Precipitation organization, or modes of delivery, can be divided into widespread, heavy mesoscale precipitating features (MPFs) and short-lived, isolated convective systems. Existing studies suggest that higher water vapor content will lead to an overall increase in precipitation, but few studies have examined changes in the precipitation modes of delivery. WRF will simulate notable wintertime and summertime precipitation events in the Southeast US under the current and future climate. In general, MPFs tend to be more common during the winter as they are linked to the large-scale forcing provided by mid latitude cyclones, while isolated convective storms occur more often during the summer due to variations in surface heating. These precipitation events will be modified to resemble the future climate of the 2090s using the pseudo-global warming (PGW) approach based on an ensemble of temperature projections from the CMIP5 for several representative concentration pathways (RCPs). A comparison between the present and future runs will reveal changes in the precipitation modes of delivery. It is hypothesized that the higher water vapor content in the future simulation will result in an increase in the number of isolated convective systems, while MPFs will be more intense and longer-lasting.