Synoptic Climatology of Factors Contributing to Precipitation Over the Eastern United States

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

Atmospheric research on precipitation tends to focus on the investigation of the heaviest events. As a result, studies have not yet been able to identify those factors that lead to precipitation (e.g., moisture ridging, jet streaks, and instability) as well as combinations of those factors that effectively discriminate extreme precipitation events from ordinary ones. Generalized relationships have been identified between atmospheric fields and heavy precipitation amounts, but these relationships typically are weak and mediated strongly by other factors (e.g. geography and synoptic regimes). Furthermore, these relationships do not account for the spatial characteristics of the precipitation event. This project will explore the synoptic climatology of precipitation, with explicit attention given to links between different factors that lead to precipitation and different types of precipitation events. Sub-synoptic-scale atmospheric features associated with precipitation in the literature will be identified in the vicinity of all precipitation events occurring over 30 warm seasons across the eastern two-thirds of the U.S. Among the features that will be computed are the strength, presence, or absence of ridging features, the propagation speed and persistence of events, and locational relationships among different features. Statistical analyses will be conducted to categorize precipitation events according to the characteristics of the associated contributing factors and to combinations of characteristics associated with different types of precipitation events. The climatological analyses developed through this project will be used to establish a climatological context for case studies of extreme precipitation events reported in the literature. This project will provide a climatological basis for assessing the relative roles of various sub-synoptic-scale features in different types of precipitation events. It will determine the extent to which extreme events are associated with unusual contributing factors or unlikely combinations of factors. This project will provide fundamental insights into relationships between atmospheric patterns and the occurrence of different types of precipitation events, thereby contributing to the enhancement of precipitation forecasting as well as to understandings of a broad range of other issues associated atmospheric dynamics.