Radiative forcing from aerosol–cloud interactions enhanced by large-scale circulation adjustments

Abstract

The impact of anthropogenic aerosols on clouds is a leading source of uncertainty in estimating the effect of human activity on the climate system. The challenge lies in the scale difference between clouds (~1–10 km) and general circulation and climate (>1,000 km). To address this, we use convection-permitting simulations conducted in a long and narrow domain, to resolve convection while also including a representation of large-scale processes. We examine a set of simulations that include a sea surface temperature gradient—which drives large-scale circulation—and compare these with simulations that include no gradient. We show that the effective radiative forcing due to aerosol–cloud interactions is strongly enhanced by adjustments of large-scale circulation to aerosol. We find that an increase in aerosol concentration suppresses precipitation in shallow-convective regions, which enhances water vapour transport to the portion of the domain dominated by deep convection. The subsequent increase in latent heat release in deep-convective regions strengthens the overturning circulation and surface evaporation. These changes can explain the increase in cloudiness under higher aerosol concentrations and, consequently, the large aerosol radiative effect. This work highlights the fundamental importance of large-scale circulation adjustments in understanding the effective radiative forcing from aerosol–cloud interactions.

Decadal co‐variation of the aerosols over East Asia and the East Asian jet streams in the boreal winter

“…This TP warming would further generate increasing MTG and Ke locally, favoring strengthened upper-level winds near the Plateau (Figures 2a, 3, 4). Recent studies have provided evidence for temperature gradient changes under the influence of aerosols (Dagan et al, 2023;Shi et al, 2022). As well, a strengthening in midlatitude upper-level winds and a weakening in oceanic branch are also consistent with numerical experiments of Jiang et al ( 2017), likely indicating potential effects of anthropogenic aerosols in the co-variation.…”

Modulation of Tropical Convection‐Circulation Interaction by Aerosol Indirect Effects in Convective Self‐Aggregation Simulations of a Gray Zone Global Model

“…We note that the focus of this study is on the circulation associated with convective aggregation. The results shown in this study might differ if an SST gradient-driven circulation that resembles the Walker circulation (Chen & Wu, 2019) were included in the modeling framework (Dagan et al, 2023).…”

Large‐Scale Tropical Circulation Intensification by Aerosol Effects on Clouds

“…In recent years, considerable effort has been devoted to understanding the impact of greenhouse gas‐induced warming on the large‐scale tropical circulation (Bony et al., 2013; Held & Soden, 2006; Merlis, 2015; Neelin et al., 2003; Seager et al., 2010; Silvers et al., 2023; Voigt & Shaw, 2015). However, despite being acknowledged as a potentially significant adjustment mechanism (Dagan et al., 2023), much remains unknown about the effects of aerosols, specifically aerosol‐cloud interactions, on large‐scale circulation.…”

“…The model SAM is publicly available in M. Khairoutdinov (2023). The data presented in this study is publicly available at https://zenodo.org/records/10408686 (Dagan, 2023).…”