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

大气对降水的研究往往集中在对最严重事件的调查上。因此，研究尚未能够确定那些导致降水的因素(例如，湿润隆起、急流条纹和不稳定)以及这些因素的组合，这些因素有效地区分极端降水事件和普通降水事件。已经确定了大气场和强降雨量之间的普遍关系，但这些关系通常很弱，受到其他因素(例如地理和天气制度)的强烈影响。此外，这些关系没有考虑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。与文献中的降水有关的次天气尺度大气特征将在美国东部三分之二的30个暖季发生的所有降水事件的附近确定。将计算的特征包括脊状特征的强度、存在或不存在、事件的传播速度和持续性以及不同特征之间的位置关系。将进行统计分析，根据相关促成因素的特点以及与不同类型降水事件有关的特征组合，对降水事件进行分类。通过该项目开发的气候学分析将被用来为文献中报告的极端降水事件的个案研究确定气候学背景。该项目将为评估各种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。该项目将对大气模式和不同类型降水事件的发生之间的关系提供基本见解，从而有助于加强降水预报，并有助于理解与大气动力学有关的广泛其他问题。

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.