Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Environment and Ecology, Ministry of Education, Ocean University of China, Qingdao, 266100, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China.
Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Environment and Ecology, Ministry of Education, Ocean University of China, Qingdao, 266100, China.
Chemosphere. 2020 Nov;258:127335. doi: 10.1016/j.chemosphere.2020.127335. Epub 2020 Jun 10.
In this study, the spatial pattern and temporal evolution of PM over North China Plain (NCP) and Northeast China (NEC) during 2014-2018 was investigated. The annual mean PM shows clear decreasing trends over time, but the seasonal mean PM as well as the seasonal total duration and frequency of haze days shows large inter-annual fluctuation. Based on the atmospheric stagnation index (ASI), this study examined the correlation between ASI and haze events over NCP and NEC. Detailed analysis indicates that location dependency exists of ASI in the capability of capturing the haze events, and the ability is limited in NCP. Therefore, we first propose two alternative methods in defining the ASI to either account for the lag effect or enlarge the threshold value of wind speed at 500 hPa. The new methods can improve the ability of ASI to explain the haze events over NEC, though marginal improvement was achieved in NCP. Furthermore, this study constructed the equation based on the boundary layer height and wind speed at 10-meter, apparently improving the ability in haze capture rate (HCR), a ratio of haze days during the stagnation to the total haze days. Based on a multi-model ensemble analyses under Representative Concentration Pathway (RCP) 8.5, we found that by the end of this century, climate change may lead to increases in both the duration and frequency of wintertime stagnation events over NCP. In contrast, the models predict a decrease in stagnant events and the total duration of stagnation in winter over NEC.
本研究调查了 2014-2018 年期间华北平原（NCP）和东北（NEC）地区 PM 的时空分布特征和演变规律。年平均 PM 呈明显的下降趋势，但季平均 PM 以及霾日的总持续时间和频率均存在较大的年际波动。基于大气静稳指数（ASI），本研究探讨了 ASI 与 NCP 和 NEC 霾事件的相关性。详细分析表明，ASI 在捕捉霾事件方面存在位置依赖性，其能力在 NCP 地区有限。因此，我们首先提出了两种替代方法来定义 ASI，以考虑滞后效应或扩大 500 hPa 风速的阈值。新方法可以提高 ASI 解释 NEC 地区霾事件的能力，尽管在 NCP 地区仅略有改善。此外，本研究基于 10 米高度的边界层高度和风速构建了一个方程，明显提高了霾捕获率（HCR）的能力，即静滞期间的霾日数与总霾日数的比值。基于 RCP8.5 下的多模式集合分析，我们发现到本世纪末，气候变化可能导致 NCP 地区冬季静滞事件的持续时间和频率增加。相比之下，模型预测冬季静滞事件和静滞总持续时间在 NEC 地区会减少。
