The forgotten role of wave dynamics in modulating the low cloud response to warm pool warming

TL;DR

This paper reveals that Rossby wave dynamics, rather than just QE-WTG theory, play a crucial role in modulating low cloud responses to warm pool warming, affecting the global radiative balance.

Contribution

It demonstrates that Rossby waves significantly influence low cloud cover changes, challenging the prevailing QE-WTG-based explanations.

Findings

Rossby waves dominate low-cloud response over the East Pacific.

Deep tropical responses primarily drive the global radiative anomalies.

Low cloud cover decreases due to Rossby wave activity, contrary to previous assumptions.

Abstract

The Pattern Effect describes the dependence of top-of-atmosphere radiation anomalies on changes in the pattern of sea surface temperatures. The emerging consensus in the field explains the impact of Pacific warm pool temperature on radiation using Convective Quasi-Equilibrium Weak Temperature Gradient (QE-WTG) theory: warm pool warming leads to increase in free-tropospheric temperatures across the tropics, a strengthening of inversion, increased cloud cover in the East Pacific low cloud decks, and negative radiative anomalies. Here we call on overlooked past results and new simulations from the Energy Exascale Earth System model to show that Rossby waves dominate the low-cloud response over the subtropical East Pacific low cloud decks, leading to decrease cloud cover in the low cloud decks. While the global radiative response is negative and consistent with QE-WTG, it is dominated by the response of the deep tropics, rather than the subtropical low cloud decks.