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，也被称为百慕大高压)的变化，这是夏季在北大西洋副热带上空形成的一个巨大的地面高压单体，影响美国东南部(美国东南部)的天气和气候。主要调查人员最近的工作表明，与前30年相比，纳什在过去30年里增强了，而且伴随着增强的是向西扩展。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纳什西部在过去30年中经历了较大的南北变化，这些变化与这一时期美国东南部降水的高度变化有关。这项赠款下的工作旨在通过数据诊断和数值模拟，在观测和气候模型模拟中确定和描述NASH变化的原因。以往的研究表明，本地和远程非绝热加热在NASH的季节发展和维持中都起着重要的作用。将在这里开展的工作旨在确定和量化这些加热在年际和年代际时间尺度上的变化，并评估它们对纳什年际至年代际变化的相对贡献。除了它的科学价值，这项工作还具有更广泛的影响，因为美国东南部地区的降水波动对社会产生了影响，美国东南部是一个人口稠密的地区，拥有大量的农业部门。此外，该项目将支持两名研究生，从而为这一领域未来的科学队伍提供支持。

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.