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

点击翻译按钮获取中文摘要

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.