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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-414
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
07 Jun 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Investigation of short-term effective radiative forcing of fire aerosols over North America using nudged hindcast ensembles
Yawen Liu1,2, Kai Zhang2, Yun Qian2, Yuhang Wang3, Yufei Zou3, Yongjia Song3, Hui Wan2, Xiaohong Liu4, and Xiu-Qun Yang1 1School of Atmospheric Sciences, Nanjing University, Nanjing, China
2Pacific Northwest National Laboratory, Richland, Washington, USA
3School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
4Department of Atmospheric Science, University of Wyoming, Laramie, Wyoming, USA
Abstract. Aerosols from fire emissions can potentially have large impact on clouds and radiation. However, fire aerosol sources are often intermittent and their effect on weather and climate is difficult to quantify. Here we investigated the short-term effective radiative forcing of fire aerosols using the global aerosol-climate model Community Atmosphere Model Version 5 (CAM5). Different from previous studies, we used nudged hindcast ensembles to quantify the forcing uncertainty due to the chaotic response to small perturbations in the atmosphere state. Daily mean emissions from three fire inventories were used to consider the uncertainty in emission strength and injection heights. The simulated aerosol optical depth (AOD) and mass concentrations were evaluated against in-situ measurements and re-analysis data. Overall, the results show the model has reasonably good predicting skills. Short (10-day) nudged ensemble simulations were then performed with and without fire emissions to estimate the effective radiative forcing. Results show fire aerosols have large effects on both liquid and ice clouds over the two selected regions in April 2009. For the 10-day average, we found a large ensemble spread of regional mean shortwave cloud radiative effect over Southern Mexico (15.6 %) and the Central U.S. (64.3 %), despite that the regional mean AOD time series are almost indistinguishable during the 10-day period. Moreover, the ensemble spread is much larger when using daily averages instead of 10-day averages. For the case investigated here, a minimum of 9 ensemble members is necessary to get a reasonable estimate of the ensemble mean and spread of the forcing on individual days. This demonstrates the importance of using a large ensemble of simulations to estimate the short-term effective aerosol radiative forcing.

Citation: Liu, Y., Zhang, K., Qian, Y., Wang, Y., Zou, Y., Song, Y., Wan, H., Liu, X., and Yang, X.-Q.: Investigation of short-term effective radiative forcing of fire aerosols over North America using nudged hindcast ensembles, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-414, in review, 2017.
Yawen Liu et al.
Yawen Liu et al.

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Short summary
Fire aerosols have large impact on weather and climate through their affect on clouds and radiation, but is difficult to quantify. Here we investigated the short-term effective radiative forcing of fire aerosols using the nudged hindcast ensemble simulations from global aerosol-climate model. Results show large effects of fire aerosols on both liquid and ice cloud and large ensemble spread of regional mean shortwave cloud radiative forcing over Southern Mexico and the Central U.S.
Fire aerosols have large impact on weather and climate through their affect on clouds and...
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