A Synoptic Framework for Forecasting the Urban Rainfall Effect Using Composite and K-Means Cluster Analyses
A Synoptic Framework for Forecasting the Urban Rainfall Effect Using Composite and K-Means Cluster Analyses
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使用复合和 K 均值聚类分析预测城市降雨影响的天气框架
DOI：
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发表时间：
2022
影响因子：
4.6
通讯作者：
Marshall Shepherd
中科院分区：
文献类型：
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作者：
J. McLeod;Marshall Shepherd
观测和数值模拟研究继续确认存在的“城市降雨效应”（URE），或一个明显的异常，在温暖的季节降水，由于城市化。然而，文献一直缺乏对URE的可预测性的进展。格鲁吉亚的亚特兰大一直出现在文献中，因为它的城市降雨异常研究。使用多传感器降水估计（MPE）数据集和ERA中期再分析数据集，18年的时间（2002-2019）进行了检查。三个相似但不同的方法被用来定义城市降雨日（URD），或亚特兰大城市化地区的降水量大于周围农村地区的时期。合成，风玫瑰，和k-均值聚类分析的组合提取的天气框架支持的URE在格鲁吉亚亚特兰大。天气尺度合成分析表明，有一个一致的气象成分，需要产生URD，包括弱于平均水平的西南到西北气流在700百帕，大量的水分在整个对流层柱，和背景低层辐合流。复合大气探测显示，有增强的水分在整个对流层柱URD，导致边缘不稳定，有利于局部对流在亚特兰大大都市区。该研究还清楚地说明了在亚特兰大大都市区的温暖季节中，URE存在的频率（大约8%的时间）。总之，这个天气框架将有助于预测的URE在亚特兰大，可以很容易地应用到其他城市。
Observational and numerical modeling studies continue to affirm the existence of the “urban rainfall effect” (URE), or a discernible anomaly in warm season precipitation due to urbanization. However, the literature has been lacking a progression towards the predictability of the URE. Atlanta, Georgia has consistently appeared in the literature because of its well-studied urban rainfall anomalies. Using the Multi-sensor Precipitation Estimates (MPE) dataset and the ERA-Interim reanalysis dataset, an 18-year period (2002–2019) is examined. Three similar but distinct methods are used to define urban rainfall days (URDs), or periods when the precipitation in the urbanized areas of Atlanta are greater than the surrounding rural areas. A combination of compositing, wind rose, and k-means cluster analyses are employed to extract the synoptic framework supportive of the URE in Atlanta, Georgia. The synoptic-scale compositing analysis reveals that there are a consistent set of meteorological ingredients that are needed to produce an URD, including weaker-than-average southwesterly-to-northwesterly flow at 700 hPa, copious amounts of moisture throughout the tropospheric column, and a background low-level convergent flow. Composite atmospheric soundings reveal that there is enhanced moisture throughout the tropospheric column on URDs, leading to marginal instability that favors localized convection across the Atlanta metropolitan area. The study also provides clarity on how often the URE is present (roughly 8% of the time) during warm season days across the Atlanta metropolitan area. Taken together, this synoptic framework will aid in the forecasting of the URE in Atlanta and can be easily applied to other cities.