Preprints
https://doi.org/10.5194/egusphere-2024-1021
https://doi.org/10.5194/egusphere-2024-1021
16 Apr 2024
 | 16 Apr 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Cloud water adjustments to aerosol perturbations are buffered by solar heating in non-precipitating marine stratocumuli

Jianhao Zhang, Yao-Sheng Chen, Takanobu Yamaguchi, and Graham Feingold

Abstract. Marine low-level clouds are key to the Earth’s energy budget due to their expansive coverage over global oceans and their high reflectance of incoming solar radiation. Their responses to anthropogenic aerosol perturbations remain the largest source of uncertainty in estimating the anthropogenic radiative forcing of climate. A major challenge is the quantification of the cloud water response to aerosol perturbations. In particular, the presence of feedbacks through microphysical, dynamical and thermodynamical pathways at various spatial and temporal scales could augment or weaken the response. Central to this problem is the temporal evolution in cloud adjustment, governed by entangled feedback mechanisms. We apply an innovative conditional Monte Carlo subsampling approach to a large ensemble of diurnal large-eddy simulation of non-precipitating marine stratocumulus to study the role of solar heating in governing the evolution in the relationship between droplet number and cloud water. We find a persistent negative trend in this relationship at night, confirming the role of microphysically enhanced cloud-top entrainment. After sunrise, the evolution in this relationship appears buffered and converges to ∼ -0.2 in the late afternoon. This buffering effect is attributed to a strong dependence of cloud-layer shortwave absorption on cloud liquid water path. These diurnal cycle characteristics further demonstrate a tight connection between cloud brightening potential and the relationship between cloud water and droplet number at sunrise, which has implications for the impact of the timing of advertent aerosol perturbations.

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Jianhao Zhang, Yao-Sheng Chen, Takanobu Yamaguchi, and Graham Feingold

Status: open (until 12 Jun 2024)

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  • RC1: 'Comment on egusphere-2024-1021', Anonymous Referee #1, 13 May 2024 reply
Jianhao Zhang, Yao-Sheng Chen, Takanobu Yamaguchi, and Graham Feingold
Jianhao Zhang, Yao-Sheng Chen, Takanobu Yamaguchi, and Graham Feingold

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Short summary
Quantifying cloud response to aerosol perturbations presents a major challenge to understanding the human impact on climate. Using a large number of process-resolving simulations of marine stratocumulus, we show that solar heating plays an important role in governing this response, such that a persistent negative trend is buffered by a negative feedback mechanism after sunrise. It provides implications for the dependence of cloud cooling effect on the timing of advertent aerosol perturbations.