Planetary Waves drive South America’s Monsoon rains

12/20/2018 - Monsoon rainfall in South America is to a large extent driven by huge airstreams high up in the atmosphere, a new study finds. Using innovative methods to explore teleconnections between different parts of the world, the scientists found evidence that the so-called Rossby waves – airstreams swinging from the tropics to Antarctica and back while circling the globe – are key for the variability in regional precipitation especially in parts of Brazil and Argentina. This has been assumed before but, to the knowledge of the authors, never been properly conceptualized and detected in actual data.
Planetary Waves drive South America’s Monsoon rains

“Our findings are of great relevance for some densely populated areas, especially the surroundings of Sao Paulo and Buenos Aires,” says Maximilian Gelbrecht from the Potsdam Institute for Climate Impact Research. “We hope that this can improve weather forecasting which becomes ever more important in times of climate change.” While the study is not about climate impacts, the region has been struck by some severe droughts in the past years which might have a link to global warming. Hence the interest of better understanding rainfall variability. Previous research by other scientists investigated the link between global warming and changes in Rossby wave behavior.

“The present study is just another outcome of our complex systems science,” says project lead Jürgen Kurths from PIK. “While our approach is based on high-end mathematics, it yields practical insights into regional rainfall, which really matters to the affected people.”

Article: M. Gelbrecht, N. Boers, J. Kurths (2018): Phase coherence between precipitation in South America and Rossby waves. Science Advances 4, eaau3191 [DOI:10.1126/sciadv.aau3191]

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