Collaborative Research: Understanding Long-Term Variability in the North Atlantic Subtropical High Driven by Evolving Tropical and Subtropical Large-Scale Heating

该项目研究北大西洋副热带高压（NASH，也称为百慕大高压）的变化，这是夏季在北大西洋副热带上空形成的一个大的表面高压单元，影响美国东南部的天气和气候。主要研究人员最近的工作表明，与前30年相比，NASH在过去30年中有所加强，并且这种加强伴随着向西扩张。在温室气体浓度增加对气候影响的模型模拟中也发现了类似的趋势。此外，与美国东南部重叠的NASH西部在过去30年中经历了更大的南北移动，这些移动与此期间美国东南部降水量变化加剧有关。这项资助的工作旨在通过数据诊断和数值模拟来确定和描述NASH在观测和气候模型模拟中变化的原因。以往的研究表明，本地和远程非绝热加热发挥重要作用的季节性发展和维持的NASH。在这里进行的工作旨在确定和量化这些加热的年际和年代际时间尺度上的变化，并评估其相对贡献的年际到年代际的变化在NASH。除了其科学价值外，这项工作还具有更广泛的影响，因为美国东南部降水波动的社会影响，这是一个人口稠密的地区，拥有大量的农业部门。此外，该项目将资助两名研究生，从而为该领域未来的科学工作者提供资金。

This project examines changes in the North Atlantic Subtropical High (NASH, also referred to as the Bermuda High), a large cell of high surface pressure that forms over the subtropical North Atlantic in summer and affects the weather and climate of the southeastern United States (SE US). Recent work by the principal investigators shows that the NASH has intensified in the past 30 years compared to the previous 30-year period, and that the intensification was accompanied by a westward expansion. Similar trends are also found in model simulations of the effect of increased greenhouse gas concentrations on climate. In addition, the western portion of the NASH, which overlaps the SE US, has experienced larger north-south shifts during the past 30 years, and these shifts are associated with heightened variation in SE US precipitation during this period. Work under this grant aims to identify and characterize the causes of the changes of the NASH in observations and climate model simulations through data diagnosis and numerical modeling. Previous studies suggest that both local and remote diabatic heating play important roles in the seasonal development and maintenance of the NASH. Work to be conducted here seeks to identify and quantify the changes of these heating on interannual and interdecadal timescales, and assess their relative contributions to the interannual to interdecadal variability in the NASH. In addition to its scientific merit, the work has broader impacts due to the societal impacts of precipitation fluctuations over the SE US, a populous region with a substantial agricultural sector. In addition, the project will support two graduate students, thereby providing for the future scientific workforce in this area.