Springtime Onset of Isolated Convection Precipitation across the Southeastern United States: Framework and Regional Evolution
Springtime Onset of Isolated Convection Precipitation across the Southeastern United States: Framework and Regional Evolution
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DOI：
10.1175/mwr-d-19-0279.1
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发表时间：
2020-02
影响因子：
3.2
通讯作者：
T. Rickenbach;R. Ferreira;Hannah C Wells
中科院分区：
文献类型：
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作者：
T. Rickenbach;R. Ferreira;Hannah C Wells
本研究探讨了2009-12年期间，在美国东南部（SE）孤立对流的春季过渡到夏季降水制度的地理和时间特征，使用高分辨率的地面雷达为基础的降水数据集。孤立对流在此是指雷达图像中水平尺寸小于100公里的孤立元素或小的降水簇。虽然美国东南部没有季风气候，它是有用的应用季风爆发的既定框架来研究夏季孤立对流制度的开始的时间和区域变化。总体而言，美国东南部地区的孤立对流雨发生在5月下旬。4月中旬开始在佛罗里达南部开始，5月上旬至中旬几乎同时在东南沿海平原继续。在北方，从弗吉尼亚州到俄亥俄州山谷，发病通常发生得更晚（6月中旬至7月初），发病时间更多变。发病时间的尖锐性在沿海平原和佛罗里达最为明显。结果表明，在即将进行的研究中，孤立的对流在春季开始的时间可能会触发特定的天气尺度事件逐渐季节性变化的大气条件，包括热带气旋路径，对流不稳定，北大西洋副热带高压的向西迁。这种方法可以提供一个有用的框架，在观测和模拟的背景下，亚热带地区降水的长期变化进行评估。
This study examines the geographic and temporal characteristics of the springtime transition to the summer precipitation regime of isolated convection in the southeastern (SE) United States during 2009–12, using a high-resolution surface radar-based precipitation dataset. Isolated convection refers herein to isolated elements or small clusters of precipitation in radar imagery less than 100 km in horizontal dimension. Though the SE United States does not have a monsoon climate, it is useful to apply the established framework of monsoon onset to study the timing and regional variation of the onset of the summer isolated convection regime. Overall, isolated convection rain onset in the SE U.S. domain occurs in late May. Onset begins in south Florida in mid-April, continuing nearly simultaneously across the southeastern coastal plain in early to mid-May. In the northern domain, from Virginia to the Ohio Valley, onset generally occurs much later (mid-June to early July) with more variable onset timing. The sharpness of onset timing is most evident in the coastal plain and Florida. Results suggest the hypothesis, to be examined in a forthcoming study, that the timing of isolated convection onset in the spring may be triggered by specific synoptic-scale events within gradual seasonal changes in atmospheric conditions including extratropical cyclone tracks, convective instability, and the westward migration of the North Atlantic subtropical high. This approach may offer a useful framework for evaluating long-term changes in precipitation for subtropical regimes in an observational and modeling context.