Subtropical Midsummer Droughts

这项研究侧重于一种单一现象，即亚热带仲夏干旱(从技术上讲，这不是一种干旱，但在美洲海域雨季期间的年降水气候循环中属于最低值)。调查员将从三个不同的空间尺度来研究这个问题。在最小的尺度上，将研究最终提供降雨的局部大气边界层和对流云过程，以找出降雨量减少的原因。在区域尺度上，将研究海洋-陆地对比、上游效应和反馈以及地形对流量和降水的影响等特征。在最大尺度上，PI将研究大尺度大气环流特征对全球大气背景状态的作用。许多更大规模的研究都基于这样的假设，即北大西洋副热带高压是“干旱”的驱动力。然而，云尺度的工作是进行过程尺度调查的地方，而区域尺度将这些影响联系在一起。研究将在三个平行的交叉轨道上进行：观测分析、动力学诊断和建模。PI计划支持一名单独的博士生，或者可能是两名连续的硕士学生，专注于每一条赛道。结果应该是更好地理解区域气候。这项研究还可能对北美亚热带和美国南部的天气和气候预测产生积极影响，包括对大西洋和东太平洋飓风的预测。

This study is focused on a single phenomenon, the subtropical midsummer drought (which is technically not a drought but a minimum in the climatological annual cycle of precipitation during the rainy season in the inter-American seas region). The investigator will approach the problem at three different spatial scales. At the smallest scale, local atmospheric boundary layer and convective cloud processes that ultimately deliver rainfall will be studied to discern why precipitation diminshes. At the regional scale, features such as ocean-land contrasts, upstream effects and feedbacks, and orographic influences on flow and precipitation will be studied. On the largest scale, the PI will examine the role of large-scale general circulation features on the background state of the global atmosphere. Much of the larger-scale work pivots on the hypothesis that the North Atlantic subtropical high is a driving force for the "drought". However, the cloud-scale work is where the process-scale investigations will occur, and the regional scale links these effects together. The research will be pursued on three parallel cross-cutting tracks: observational analysis, dynamical diagnosis and modeling. The PI plans to support a separate PhD student, or perhaps a pair of consecutive MS students, to focus on each track. A better understanding of regional climate should result. There also could be positive impacts on weather and climate prediction across subtropical North America and the southern United States including forecasting of Atlantic and eastern Pacific hurricanes as a result of this research.