Influence of Northeast Monsoon cold surges on air quality in Southeast Asia
Influence of Northeast Monsoon cold surges on air quality in Southeast Asia
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DOI：
10.1016/j.atmosenv.2017.07.047
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发表时间：
2017-10-01
影响因子：
5
通讯作者：
Harris, N. R. P.
中科院分区：
文献类型：
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作者：
Ashfold, M. J.;Latif, M. T.;Harris, N. R. P.
臭氧（O3）是一种重要的地面污染物。近几十年来，在东亚，O3前体的O3水平和排放显著增加，并且这种O3向东穿过太平洋的出口是有据可查的。在这里，我们表明，东亚03也向南输送到热带东南亚（SE）亚洲在东北季风（NEM）季节（定义为11月至2月），这条运输途径是特别强大的“冷雨”。我们的分析采用了再分析数据和马来西亚半岛地面站点的测量数据，两者都涵盖了2003-2012年，沿着轨迹计算。使用冷涌指数（925 hPa的偏北风平均超过105-110度E，5度N）来定义NEM风的亚季节加强，我们发现最大的变化在一个区域覆盖了大部分的印度支那半岛和周边海域。在这里，通过监测大气成分和气候（MACC）再分析计算的O3和另一种关键污染物一氧化碳的水平在冷涌期间分别平均升高>40%（类似于15 ppb）和>60%（类似于80 ppb）。此外，在东南亚更广泛的地区，当地下午的世界卫生组织的空气质量指南03（100 μ g m（-3），或类似于50 ppb，平均超过8小时）的变化主要发生在这些寒潮期间。在马来西亚半岛东海岸的地面站点和MACC再分析的相应部分，可用的03观测值的逐日变化是相似的，并且显然与冷涌有关。然而，观察到的O3水平通常类似于比MACC再分析低10-20 ppb。我们发现，这些观测结果也受到当地城市污染的影响。与过去的工作一致，我们发现每年的变化与厄尔尼诺南方涛动（ENSO）的冷涌活动，但这似乎并不是主导影响的ENSO在这一地区的大气成分。总体而言，我们的研究表明，东亚污染对东南亚空气质量的影响在NEM期间可能至少与相应的，充分研究的北美春季影响一样大。需要加强区域观测能力和进行化学模拟研究，以充分弄清这种长期影响相对于当地进程的重要性。(C)2017爱思唯尔有限公司版权所有
Ozone (03) is an important ground-level pollutant. 03 levels and emissions of 03 precursors have increased significantly over recent decades in East Asia and export of this 03 eastward across the Pacific Ocean is well documented. Here we show that East Asian 03 is also transported southward to tropical Southeast (SE) Asia during the Northeast Monsoon (NEM) season (defined as November to February), and that this transport pathway is especially strong during 'cold surges'. Our analysis employs reanalysis data and measurements from surface sites in Peninsular Malaysia, both covering 2003-2012, along with trajectory calculations. Using a cold surge index (northerly winds at 925 hPa averaged over 105-110 degrees E, 5 degrees N) to define sub-seasonal strengthening of the NEM winds, we find the largest changes in a region covering much of the Indochinese Peninsula and surrounding seas. Here, the levels of 03 and another key pollutant, carbon monoxide, calculated by the Monitoring Atmospheric Composition and Climate (MACC) Reanalysis are on average elevated by, respectively, >40% (similar to 15 ppb) and >60% (similar to 80 ppb) during cold surges. Further, in the broader region of SE Asia local afternoon exceedances of the World Health Organization's air quality guideline for 03 (100 mu g m(-3), or similar to 50 ppb, averaged over 8 h) largely occur during these cold surges. Day-to-day variations in available 03 observations at surface sites on the east coast of Peninsular Malaysia and in corresponding parts of the MACC Reanalysis are similar, and are clearly linked to cold surges. However, observed 03 levels are typically similar to 10-20 ppb lower than the MACC Reanalysis. We show that these observations are also subject to influence from local urban pollution. In agreement with past work, we find year-to-year variations in cold surge activity related to the El Nino-Southern Oscillation (ENSO), but this does not appear to be the dominant influence of ENSO on atmospheric composition in this region. Overall, our study indicates that the influence of East Asian pollution on air quality in SE Asia during the NEM could be at least as large as the corresponding, well-studied springtime influence on North America. Both an enhanced regional observational capability and chemical modelling studies will be required to fully untangle the importance of this long-range influence relative to local processes. (C) 2017 Elsevier Ltd. All rights reserved.