Dependence of fast changes in global and local precipitation on the geographical location of aerosol absorption

Abstract

Anthropogenic aerosol interacts strongly with incoming solar radiation, perturbing the Earth's energy budget and precipitation on both local and global scales. Understanding these changes in precipitation has proven particularly difficult for the case of absorbing aerosol, which absorbs a significant amount of incoming solar radiation and hence acts as a source of localized diabatic heating to the atmosphere. In this work, we use an ensemble of atmosphere-only climate model simulations forced by identical aerosol absorption perturbations across the globe to develop a basic physical understanding of how this localized heating impacts the atmosphere and how these changes impact on precipitation both globally and locally. In agreement with previous studies we find that aerosol absorption causes a decrease in global-mean precipitation, but we also show that even for identical aerosol optical depth perturbations, the global-mean precipitation change varies by over an order-of-magnitude depending on the location of the aerosol burden. Our experiments also demonstrate that the local precipitation response to aerosol absorption is opposite in sign between the tropics and the extratropics, as found by previous work. We then show that this contrasting response can be understood in terms of different mechanisms by which the large-scale circulation responds to heating in the extratropics and in the tropics. We provide a simple theory to explain variations in the local precipitation response to tropical aerosol absorption. Our work highlights that the spatial pattern of aerosol absorption and its interactions with circulation are a key determinant of its overall climate impact and must be taken into account when developing our understanding of aerosol-climate interactions.

On the sensitivity of aerosol-cloud interactions to changes in sea surface temperature in radiative-convective equilibrium

“…Furthermore, the role of other modeling choices, such as horizontal and vertical resolution and the role of boundary conditions (Dagan et al, 2022) in our results should be examined in future work. In addition, in this work we excluded aerosol-radiation interactions, which could drastically alter TOA energy gain (Bellouin et al, 2020;Williams et al, 2023), and as such could be of interest. Finally, our work is based on single-model simulations.…”

The Potential of Absorbing Aerosols to Enhance Extreme Precipitation

“…These factors warrant further investigation and may refine our understanding of the relationship between absorbing aerosols and extreme precipitation (e.g., see Dagan et al (2023) for large domain simulations of hothouse climate episodic deluges regime). Furthermore, previous studies using global climate simulations (Dagan et al, 2021;Persad, 2023;Williams et al, 2023) demonstrated that the location of the absorbing aerosol perturbation matters for the local-and global-mean precipitation response. Thus, it will also be interesting to examine the response of extreme precipitation to different geographical locations of aerosol perturbation in global convective-resolving simulations.…”

“…Understanding the intricate processes that govern precipitation is crucial for addressing water resource management, flood risks, and climate change impacts. Recent research has highlighted the significant role of aerosols, particularly absorbing aerosols, in modulating the energy budget of the atmosphere and subsequently influencing precipitation patterns (Dagan et al., 2019; Herbert et al., 2021; Liu et al., 2018; Samset, 2022; Sand et al., 2020; Williams et al., 2023). Absorbing aerosols, such as black carbon (Bond et al., 2013), possess the ability to absorb solar radiation and alter the vertical temperature gradient (Lu et al., 2020; Stjern et al., 2017; Wilcox et al., 2016), thereby perturbing the convective dynamics and thermodynamic conditions conducive to precipitation.…”