Seasonal variability of modes-of-delivery of precipitation within midlatitude cyclones in the Southeastern United States

In this study five years of data (2009-2012) from the National Mosaic and Multi-sensor Quantitative Precipitation Estimation (NMQ) radar are analyzed to produce a seasonal climatology of the precipitation organization that occurs within midlatitude cyclones that affect the SE US. An algorithm is applied to the NMQ radar data to identify the different modes-of-delivery of precipitation present in midlatitude cyclones that affect the SE US. Examples of modes-of-delivery that occur in North Carolina within various synoptic regimes include short duration and spatially heterogeneous convective cells, large mesoscale convective systems, widespread long-lasting frontal precipitation, tropical cyclones, and winter precipitation. Since different modes-of-delivery may produce similar time-averaged precipitation totals, but have very different climate and hydrological impacts, a mode-of-delivery climatology provides benefits beyond those of a standard precipitation climatology.

Our analysis quantifies the presence of these different modes of delivery in midlatitude cyclones for each season of the year, providing detailed information on the rainfall structure of these important storms. Data from the North American Regional Reanalysis will be used to show how changes in the precipitation mode-of-delivery relate to changes in the synoptic-scale environment of the midlatitude cyclone, giving a glimpse into the mechanisms for rainfall organization.

This climatology will result in improvements to regional climate model forecasting and hydrological simulations on the watershed scale.