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

Xiaoting Sun,Rui Luo,Qingquan Li,Yihui Ding,Qinghua Ding,Christopher Castro,Shih-Yu Simon Wang,Dániel Topál,Haiyan Teng

doi:10.1038/s41467-022-28911-7

Abstract

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.

Highlights

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
In all, the tropical processes leading to the waviness in the Z200 trends (Fig. 1) are manifold and can be summarized in a schematic diagram (Fig. 7a): first, the recent sea surface temperature (SST) and precipitation trends in the tropical Pacific and its associated upper-level convergence/divergence anomalies (Supplementary Fig. 10) generate strong Rossby wave source (RWS, Methods) over the Western North Pacific, which in turn creates propagating Rossby waves at upper levels and subsequently disturbs the mean flow (Fig. 7a)
The westerly jet acts as a waveguide for the perturbation to propagate downstream from the Pacific to the North Atlantic, while the excited disturbance sends off wave energy that is accumulated at the jet exit region over the Northeast Atlantic, which is manifested as a lowpressure center (Fig. 7b)

Summary

Introduction

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. 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. The purpose of this research is to investigate these two perspectives and shed light on the profound midlatitude circulation changes alongside the concurrent Arctic warming and anthropogenic forcing

Objectives

Methods

Results

Conclusion