Vertical profile and radiative forcing of black carbon in a winter pollution period over Chengdu, China
Vertical profile and radiative forcing of black carbon in a winter pollution period over Chengdu, China
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DOI：
10.1016/j.atmosres.2021.105896
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发表时间：
2021-10
影响因子：
5.5
通讯作者：
Yuan Liang;Zhang Xiaoling;Che Yuzhang;Xia Xiang-Ao;Liu Xuan;Zhao Tianliang;Song Minghao
中科院分区：
文献类型：
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作者：
Yuan Liang;Zhang Xiaoling;Che Yuzhang;Xia Xiang-Ao;Liu Xuan;Zhao Tianliang;Song Minghao
利用安装在系留气球上的微型气压计，测量了2017年冬季污染期间成都上空BC质量浓度的垂直分布。成都是四川盆地的一个特大城市。本次观测经历了严重的空气污染，平均地面BC为11.1g·mμ·m−3，是成都2018年年平均水平的两倍多。现有的68条BC垂直廓线可分为5种类型：A型(18%)是BC的均匀垂直分布，混合层高度难以识别；B型(26%)BC在ML内也是均匀分布的，但在ML上方迅速减小；C型(7%)是单峰分布，在悬浮逆温形成时BC峰在ML内；D型(29%)BC在近地面层积累，随着高度的增加而迅速减少；E型(20%)是双峰或三峰分布，BC峰在ML顶部附近。从中午到下午，A型和B型占优势，而C型和E型在晚上和夜间起关键作用。不同的BC垂直格局主要与ML和局地排放的演变有关。对于所有五种类型，计算的BC辐射强迫(FBC)在地表为负，而在廓线顶部(顶部)为正，表明BC对大气辐射的净吸收。表面和顶部的BCat绝对值随着柱状BC载荷的增加而增加，当考虑相同的BC载荷时，不同模式之间的BCat和表面BCat没有显著差异。而BC(HBC)对大气加热率的垂直分布与BC的垂直廓线高度相关。均匀分布的BC可以使hBC随高度呈正梯度，从而增强大气的稳定性。四川盆地西部高原地形诱发的小尺度次生环流和相对较低的热逆温对气溶胶的垂直分布有重要影响，并可导致气溶胶在距地面0.8-1.4公里处积累。这一研究有望对四川盆地BC的垂直分布有一个初步的了解，并对准确估算该地区BC的直接辐射强迫具有重要意义。
The vertical distributions of BC mass concentration (mBC) during a winter pollution period in 2017 over Chengdu, a megacity in the Sichuan Basin, China, were measured by a micro-aethalometer equipped on a tethered balloon. This observation experienced severe air pollution with an averaged ground BC of 11.1 μg·m−3, which is higher than two times the annual mean in Chengdu for 2018. The available 68 BC vertical profiles are grouped in to five types: Type A (18%) is the uniform vertical distribution of BC with an unrecognizable mixing layer (ML) height; BC in Type B (26%) is also uniformly distributed in the ML while decreases rapidly above the ML; Type C (7%) is a unimodal distribution with BC peak within the ML when the suspended temperature inversion forms; BC in Type D (29%) is accumulated in the near-ground layer and quickly decreases with height; Type E (20%) is the bimodal or trimodal distribution with BC peaks around the top of ML. Types A and B dominate from noon to afternoon, and Types C–E play critical roles during the evening and night. The different vertical patterns of BC are mainly associated with the evolution of the ML and the local emissions. For all the five types, the calculated radiative forcing of BC (fBC) is negative at the surface but positive at the top of profile (TOP), indicating the net absorption of radiation by the atmosphere due to BC. The absolute values offBCat the surface and the TOP are increased with the increase of columnar BC loading, and there is no significant difference infBCat the TOP and the surface among different patterns when the same BC loading is considered. However, the vertical distribution of atmospheric heating rate contributed by BC (hBC) is highly related to BC's vertical profile. The uniform distributed BC can result in a positive gradient ofhBCwith altitude, and thus, enhance the stability of the atmosphere. The plateau terrain induced small-scale secondary circulation and relatively lower thermal inversion in the west of the Sichuan basin have an essential effect on the vertical distribution of aerosols and can contribute to an accumulation of aerosols at 0.8–1.4 km above ground level. This study would hopefully have a preliminary understanding of the vertical distribution of BC in the Sichuan Basin, and a vital implication for accurately estimating direct radiative forcing by BC in this region.