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

关于降水的大气研究往往侧重于调查最严重的事件。 因此，研究尚未能够确定导致降水的那些因素（例如，水汽脊、急流条纹和不稳定性）以及这些因素的组合，这些因素有效地将极端降水事件与普通降水事件区分开来。 大气场和强降水量之间的一般关系已经确定，但这些关系通常是弱的，并强烈介导的其他因素（如地理和天气制度）。 此外，这些关系不占降水事件的空间特征。 该项目将探讨降水的天气气候学，明确注意导致降水的不同因素与不同类型降水事件之间的联系。 次天气尺度的大气特征与降水在文献中将被确定在附近的所有降水事件发生在30个温暖的季节在美国东部三分之二的功能，将被计算的强度，存在或不存在的脊功能，传播速度和事件的持续性，以及不同功能之间的位置关系。 将进行统计分析，根据相关促成因素的特点和与不同类型降水事件相关的特点组合，对降水事件进行分类。 通过该项目进行的气候分析将用于为文献中报告的极端降水事件的个案研究建立气候背景。 该项目将为评估不同次天气尺度特征在不同类型降水事件中的相对作用提供气候学基础。 它将确定极端事件在多大程度上与不寻常的促成因素或不太可能的因素组合有关。 该项目将提供有关大气模式与不同类型降水事件发生之间关系的基本见解，从而有助于加强降水预报以及了解与大气动力学有关的广泛的其他问题。

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.