Direct radiative effect of carbonaceous aerosols from crop residue burning during the summer harvest season in East China
Huan Yao, Yu Song, Mingxu Liu, Tingting Xu, Pin Du, Jianfeng Li, Yusheng Wu, Min Hu, and Tong Zhu
State Key Joint Laboratory of Environmental Simulation and Pollution Control, Department of Environmental Science, Peking University, Beijing, China
Received: 23 Aug 2016 – Accepted for review: 07 Nov 2016 – Discussion started: 08 Nov 2016
Abstract. The East China experiences extensive crop residue burning in fields during harvest seasons. The direct radiative effect (DRE) of carbonaceous aerosols from crop residue burning in June 2013 in East China was investigated using the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem). Absorption of organic aerosol (OA) in the presence of brown carbon (BrC) was considered using the parameterization of Saleh et al. (2014), in which the imaginary part of BrC refractive index was a function of the ratio of the black carbon (BC) and OA and wavelengths. The carbonaceous emissions from crop fires were estimated using the Moderate Resolution Imaging Spectroradiometer (MODIS) fire radiative power products with a localized crop burning-sourced BC-to-organic carbon (OC) ratio emission ratio of 0.27. The simulation results were evaluated with in situ measurements of fine particle (PM2.5) chemical components and meteorological observations. The aerosol optical depths were comparable with MODIS detections. The BC and OC peak concentrations reached 34.3 µg m−3 and 121.1 µg m−3, of which the crop residue burning contributed 86 % and 90 %, respectively. Correspondingly, the DREs of crop residue burning-sourced BC and BrC (due to absorption) reached +20.16 W m−2 and +7.17 W m−2, respectively. On average, during the harvest season, crop residue burning introduced a DRE of +0.39 W m−2 throughout East China. We found that BrC absorption and BC introduced significant positive DREs, +0.85 W m−2 and +1.05 W m−2, respectively. The BrC DRE due to scattering was stronger (−1.1 W m−2) than its DRE due to absorption. The sensitivity test showed that the BrC DRE strongly depended on the absorptivity and BC-to-OA ratio emission ratio from crop residue burning, and the volume mixing treatment could result in a higher positive DRE compared to the core/shell treatment.
Yao, H., Song, Y., Liu, M., Xu, T., Du, P., Li, J., Wu, Y., Hu, M., and Zhu, T.: Direct radiative effect of carbonaceous aerosols from crop residue burning during the summer harvest season in East China, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-759, in review, 2016.