Enhanced jet stream waviness induced by suppressed tropical Pacific convection during boreal summer

Consensus on the cause of recent midlatitude circulation changes toward a wavier manner in the Northern Hemisphere has not been reached, albeit a number of studies collectively suggest that this phenomenon is driven by global warming and associated Arctic amplification. Here, through a fingerprint analysis of various global simulations and a tropical heating-imposed experiment, we suggest that the suppression of tropical convection along the Inter Tropical Convergence Zone induced by sea surface temperature (SST) cooling trends over the tropical Eastern Pacific contributed to the increased summertime midlatitude waviness in the past 40 years through the generation of a Rossby-wave-train propagating within the jet waveguide and the reduced north-south temperature gradient. This perspective indicates less of an influence from the Arctic amplification on the observed mid-latitude wave amplification than what was previously estimated. This study also emphasizes the need to better predict the tropical Pacific SST variability in order to project the summer jet waviness and consequent weather extremes. The Northern Hemisphere summer circulation in the midlatitudes has become more meandering over the past decades, but the cause of the change remains elusive. Here the authors reveal that the waiver trending pattern results from internal climate forcing associated with sea surface temperature low frequency variability over the tropical Eastern Pacific.

Automated summary

There is no consensus on the cause of recent midlatitude circulation changes towards a wavier manner in the Northern Hemisphere, although studies suggest it is driven by global warming and Arctic amplification. Recent research indicates that a cooling trend in sea surface temperatures over the tropical Eastern Pacific has contributed to increased summertime midlatitude waviness in the past 40 years by suppressing tropical convection along the Inter Tropical Convergence Zone.