A five-year climatology of precipitation organization in the southeastern U.S: seasonal cycle and extreme events
The climatology is comprised of a pixel-based and spatial-average analysis of precipitation: frequency of occurrence, ice/liquid phase, organization, and precipitation event duration. The analysis is based on a portion of the National Mosaic and Multi-sensor Quantitative Precipitation Estimation (NMQ) three-dimensional radar reflectivity mosaic and QPE dataset. Every 15 minutes, all near-surface rainfall features > 0.5 mm/hr are identified and segregated into size categories, which determine whether or not each is associated with a mesoscale convective system (MCS) or group of isolated convective cells. Within these features, convective vs. stratiform, frozen vs. liquid precipitation, and shallow (warm) rain is identified. The duration and frequency distributions of each precipitation type at each pixel is tracked and integrated over daily, weekly, and seasonal time periods over the five-year period.
We present monthly precipitation maps that reveal the seasonal evolution of the spatial pattern and relative amounts of MCS versus isolated convection. For several extreme precipitation events (two standard deviations above the annual mean precipitation), centered on North Carolina, the time-space evolution and the relative amounts of MCS and isolated convection are examined. Results quantify the relative importance of MCS versus isolated convection for each season.