A new Asian/North American teleconnection linking clustered extreme precipitation from Indian to Canada

Abstract

Three consecutive precipitation extremes emerged in November 2021, including India-Sri Lanka flooding, East Asian blizzard, and Canadian floods. Why the catastrophic events occurred successively and whether they will become more frequent as global warming continues are unknown. Here we show they are organized by an intraseasonal Asian/North American (ANA) teleconnection consisting of two cross-Pacific wave trains fortified by dipolar diabatic heating anomalies (“wet India-dry Philippines”). The dipolar heating anomaly is shaped by multi-scale interaction between a quasi-stationary Madden-Julian Oscillation (MJO) episode and a rapidly developed La Niña over the tropical Asian monsoon region. Numerical experiments suggest that the off-equatorial heating dipole can generate the ANA pattern resembling observations, distinct from the equatorial MJO-induced teleconnection and the La Niña-induced Pacific/North American teleconnection. Philippine cooling stimulates the circum-Pacific wave train, while Indian heating produces the eastward-propagating subtropical wave train. These wave trains persistently steered cross-Pacific atmospheric rivers channeling warm-moisture-laden air to the extratropics. We suggest that the ANA teleconnection could be a new route by which multi-scale interaction between the La Niña and quasi-stationary MJO over the tropical Asian monsoon affects extratropical East Asia and North America. This work provides a unique perspective on understanding the origins of increasing collisions of extremes worldwide within a short time as the global climate warms.