Future Amplification of Moist Weather Extremes in the Midlatitudes

TL;DR

This study identifies low-level atmospheric inversions, driven by orographic heating and westerly transport, as key factors in the projected intensification of moist heatwaves and storms in midlatitude regions due to climate change.

Contribution

It uncovers the physical mechanism linking orographic warming, atmospheric inversions, and the future amplification of moist weather extremes in midlatitudes.

Findings

Moist heatwaves and storms are projected to intensify in midlatitudes.

Low-level atmospheric inversions constrain the maximum intensity of these extremes.

Orographic heating and westerly transport are critical drivers of this intensification.

Abstract

Moist heatwaves and convective storms frequently co-occur, posing compound risks. Although historically concentrated in the tropics, these moist weather extremes are projected to intensify substantially towards the midlatitudes, with regions downstream of major highland terrains, including northeastern Asia and eastern North America, emerging as hotspots of future change. Yet their physical drivers remain uncertain. Here we show that the intensification of concurrent moist heat and convection extremes in the midlatitudes is tightly constrained by changes in low-level atmospheric inversions. Specifically, we find that amplified warming over western highlands is transported downstream by prevailing westerlies, strengthening low-level thermal inversions and raising the attainable maxima of moist heat and convection. Targeted model experiments confirm the critical role of orographically elevated heating in driving these extremes. Our results reveal a mechanistic pathway for compound extremes and highlight low-level inversions as a key factor for emerging midlatitude risks of moist heat and severe weather under climate change.