ABSTRACT: Previous investigations have documented relationships between global-scale forcings and Northeast United States moisture conditions, yet the physical pathways from global-scale forcing to sub-regional moisture deficit or surplus are not well understood. This research uses eigenvector-based regionalization to confirm the existence of sub-regional moisture environments within the Northeast. Synoptic classification is used to derive daily weather types that impact these moisture environments, and evaluate the relationship between global and synoptic scales. The Palmer Drought Severity Index (PDSI) regionalization identifies 3 sub-regions across the Northeast with homogeneous moisture conditions including New England, the Eastern Great Lakes, and Mid-Atlantic Regions. All 3 regions’ PDSI conditions are predominantly associated with variations in precipitation, rather than thermal characteristics. The frequency of key precipitation-associated synoptic types can inform PDSI variability in the regions, where drier conditions are observed during growing seasons with a reduced frequency of precipitation-inducing synoptic types and an enhanced frequency of dry synoptic types. Variations in the frequencies of these synoptic types are partially explained by the phase of the various teleconnection patterns. In the case of the New England region, 14% of the variance in PDSI is explained by the frequency of synoptic type D2, and 12% of the variance in D2 is explained by variations in the Summer Atmospheric Drought Index. The New England region became significantly wetter (positive PDSI) from 1950 to 2016. This study suggests a partial cause of this trend is the increased and decreased frequencies of wet and dry synoptic types, respectively, both related to the phase of the Summer Atmospheric Drought Index.

中文翻译：

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美国东北部水分条件的区域化：天气尺度大气驱动因素分析

摘要：先前的调查已记录了全球规模强迫与美国东北部水分状况之间的关系，但从全球规模强迫到次区域水分亏缺或过剩的物理途径尚不十分清楚。这项研究使用基于特征向量的区域化方法来确认东北部地区存在次区域水分环境。天气分类法用于得出影响这些潮湿环境的每日天气类型，并评估全球尺度和天气尺度之间的关系。帕尔默干旱严重性指数（PDSI）区域划分确定了东北部3个具有均匀湿度条件的子区域，包括新英格兰，东部大湖区和中大西洋地区。这三个地区的PDSI条件主要与降水量的变化有关，而不是与热特征有关。关键的与降水相关的天气类型的频率可以告知该地区的PDSI变异性，在这些地区，生长季节期间观测到较干燥的条件，导致降水的天气类型减少，而干旱的天气类型频率增加。这些天气类型的频率变化部分由各种遥距连接模式的相位来解释。在新英格兰地区，天气类型D2的发生频率解释了PDSI中14％的变化，而夏季大气干旱指数的变化则解释了D2中12％的变化。从1950年到2016年，新英格兰地区变得非常湿润（PDSI为正值）。