Nature (2019)

In this era of anthropogenic climate change, understanding the mechanisms underlying extreme weather events could help their forecast. At the regional scale, weather systems exhibit spatial correlations — after all, when it’s raining outside, we usually expect our friends elsewhere in the city to be getting soaked too. But as Niklas Boers and colleagues have now reported, extreme rainfall events exhibit correlations over substantially longer distances.

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Martin Siepmann / imageBROKER / Alamy Stock Photo

The authors constructed a complex network whose nodes corresponded to spatial grid cells in the rainfall data. Links were placed between nodes that exhibited synchronization in days of extreme rainfall, up to ten days apart. The analysis revealed a bimodal probability density function for the link distances: a power-law decay at short scales, arising from regional weather systems, followed by a bump at around 2,500 km. This signals the presence of large-scale climate teleconnection patterns, providing evidence that far-flung extreme events may be generated by the same perturbations to the jet stream, known as Rossby waves.