雨滴形成によるモデルエアロゾル強制力の不確実性を衛星観測が制約する(Satellite Observations Constrain Model Aerosol Forcing Uncertainty Due to Raindrop Formation)

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2024-06-14 パシフィック・ノースウェスト国立研究所(PNNL)

エアロゾルと雲の相互作用(ACI)が地球の放射収支に与える影響は不確実です。本研究では、MODISとCloudSatの衛星データを用いて、海洋性液体雲の滴収集効率に関連するACI放射強制力(ERFaci)を制約する方法を示しました。E3SMv2モデルと観測データを比較し、モデルの滴形成の表現が全体的なERFaci不確実性にほとんど寄与しないことを確認しました。E3SMv2の低層液体雲の面積割合は観測と一致していますが、雲頂滴サイズが小さいバイアスがあり、このバイアスがなければERFaciはさらに強力であることが示されました。この研究は、ACIの理解と気候モデルの精度向上に貢献します。

<関連情報>

衛星観測から推定される液滴捕集効率がエアロゾルと雲の相互作用の有効放射強制力を制約する Droplet collection efficiencies inferred from satellite retrievals constrain effective radiative forcing of aerosol–cloud interactions

Charlotte M. Beall, Po-Lun Ma, Matthew W. Christensen, Johannes Mülmenstädt, Adam Varble, Kentaroh Suzuki, and Takuro Michibata
Atmospheric Chemistry and Physics  Published:07 May 2024
DOI:https://doi.org/10.5194/acp-24-5287-2024

雨滴形成によるモデルエアロゾル強制力の不確実性を衛星観測が制約する(Satellite Observations Constrain Model Aerosol Forcing Uncertainty Due to Raindrop Formation)

Abstract

Process-oriented observational constraints for the anthropogenic effective radiative forcing due to aerosol–cloud interactions (ERFaci) are highly desirable because the uncertainty associated with ERFaci poses a significant challenge to climate prediction. The contoured frequency by optical depth diagram (CFODD) analysis supports the evaluation of model representation of cloud liquid-to-rain conversion processes because the slope of a CFODD, generated from joint MODerate Resolution Imaging Spectroradiometer (MODIS)-CloudSat cloud retrievals, provides an estimate of cloud droplet collection efficiency in single-layer warm liquid clouds. Here, we present an updated CFODD analysis as an observational constraint on the ERFaci due to warm rain processes and apply it to the U.S. Department of Energy’s Energy Exascale Earth System Model version 2 (E3SMv2). A series of sensitivity experiments shows that E3SMv2 droplet collection efficiencies and ERFaci are highly sensitive to autoconversion, i.e., the rate of mass transfer from cloud liquid to rain, yielding a strong correlation between the CFODD slope and the shortwave component of ERFaci (ERFaciSW; Pearson’s  R=-0.91). E3SMv2’s CFODD slope (0.20 ± 0.04) is in agreement with observations (0.20 ± 0.03). The strong sensitivity of ERFaciSW to the CFODD slope provides a useful constraint on highly uncertain warm rain processes, whereby ERFaciSW, constrained by MODIS-CloudSat, is estimated by calculating the intercept of the linear association between the ERFaciSW and the CFODD slopes, using the MODIS-CloudSat CFODD slope as a reference.

1702地球物理及び地球化学
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