The Cross-equatorial Influences of South American Rainfall on the North Atlantic and Adjacent Continents

一个半球对另一个半球的影响是全球天气气候遥相关的重要组成部分。以前的大部分研究都集中在通过赤道的大气行星(Rossby)波的传播来研究北太平洋冬季期间东太平洋的遥相关。在美洲-大西洋部门，各种半球间遥相关路径控制着亚马逊砍伐森林和极端冷锋入侵对北美和欧洲上空天气和气候变异性的影响。其中两个悬而未决的问题是，控制这些遥相关的动态过程是什么，以及它们如何影响干旱、洪水和热带风暴的路径。这项提案将通过检验关于美洲-大西洋地区半球间遥相关路径背后的机制的三个假说来解决这一知识差距。来自该项目的见解将有助于促进我们对跨赤道遥相关的理解，并可能对改善北大西洋和周边大陆(包括北美、欧洲和非洲)的亚季节到年际气候预测能力产生影响。后者也是描述快速变化的亚马逊雨林对全球大气循环和气候的潜在影响的中心。主要的更广泛的影响包括培训来自代表性不足群体的两名研究生，指导本科生的研究。研究成果将被纳入一门大型高年级本科生理科课程。该项目还支持南美教职员工的访问，以帮助建立美国学院和大学与国际学术机构和组织的网络，特别是针对学生的网络。他们将考虑三个在不同季节运行的动力过程，这些过程与南美洲上空非绝热加热异常引起的跨赤道遥相关有关：(I)南美洲季风非绝热加热产生的Rossby波的跨赤道传播，以影响北半球冬季的北大西洋涛动；(Ii)来自亚马逊的对流耦合向东传播的开尔文波，影响北半球春季的热带大西洋地面风、海平面高度异常和刚果西部降水变率；以及(Iii)连接南美洲热带外冷空气入侵的跨赤道浅环流，影响北半球夏季热带和亚热带北大西洋的天气和气候变化。PI计划通过观察分析和一套理想化的数值模型实验来评估这些假设。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The influence of one-hemisphere on another hemisphere is an important component of global weather and climate teleconnections. Most of previous research has been focused on teleconnections over the eastern Pacific during boreal winter season through the propagation of the atmospheric planetary (Rossby) waves across the equator. Over the American-Atlantic sector, various interhemispheric teleconnection pathways control the influence of Amazonia deforestation and of extreme cold front incursions on weather and climate variability over the North American and Europe. Two of the outstanding questions are what are the dynamic processes that control these teleconnections and how they affect droughts, floods and the tracks of tropical storms. This proposal will address this knowledge gap by testing three hypotheses about the mechanisms behind the interhemispheric teleconnection pathways over the American-Atlantic sector. The insights from the project will help advance our understanding of cross-equatorial teleconnections and may have implications for improving sub-seasonal to interannual climate predictability over the North Atlantic and the surrounding continents, including North America, Europe, and Africa. The latter is also central for characterizing the potential influences of rapidly changing Amazonian rainforests on global atmospheric circulation and climate. The main broader impacts involve training of two graduate students from underrepresented groups, mentoring of undergraduate research. The research findings will be incorporated into a large upper-division undergraduate science course. The project also supports visitations of faculty members from South America to help build networks of U.S. colleges and universities, especially for students, with international academic institutions and organizations. They will consider three dynamic processes operating in different seasons responsible for cross-equatorial teleconnections originated from diabatic heating anomalies over South America: (i) cross-equatorial propagation of the Rossby waves generated by diabatic heating over the South American Monsoon to influence the North Atlantic Oscillation during boreal winter, (ii) convective coupled eastward propagating Kelvin waves from Amazonia that influences tropical Atlantic surface winds, sea-level height anomalies, and western Congo rainfall variability in boreal spring, and (iii) a shallow cross-equatorial circulation connecting cold air incursions from the extratropical South America to influence weather and climate variability of the tropical and subtropical North Atlantic in boreal summer. The PI plan to evaluate these hypotheses through observational analyses and a suite of idealized numerical model experiments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.