Temporal evolution of aerosols and their extreme events in polluted Asian regions during Terra's 20-year observations
Temporal evolution of aerosols and their extreme events in polluted Asian regions during Terra's 20-year observations
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Terra 20年观测期间亚洲污染地区气溶胶的时间演化及其极端事件
DOI：
10.1016/j.rse.2021.112541
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发表时间：
2021-06-07
影响因子：
13.5
通讯作者：
Dong, Wenjie
中科院分区：
文献类型：
--
作者：
Hu, Zhiyuan;Jin, Qinjian;Dong, Wenjie
气溶胶污染是发展中国家的一个严重环境问题。在过去的二十年里，由于人口和经济的快速增长，亚洲经历了人为气溶胶的快速变化。以气溶胶光学厚度（AOD）为代表的气溶胶负荷在本世纪是如何演变的，特别是在中国和印度实施旨在改善空气质量的清洁空气法案的过去十年中，这仍然是一个悬而未决的问题。基于Terra气溶胶反演和气溶胶再分析，中国东部的气溶胶光学厚度趋势在2010年检测到一个变化点，而印度次大陆的气溶胶光学厚度趋势持续增加，从2000年到2019年没有检测到变化点。在华东地区，2000 - 2010年（以下简称前期）的气溶胶光学厚度呈正趋势（+0.11 +/-0.022 decade- 1），而2011 - 2019年（以下简称后期）的气溶胶光学厚度呈负趋势（-0.26 +/-0.027 decade- 1）。在印度次大陆，从2000年到2019年（以下称整个时期），检测到持续的正趋势（+0.04 +/-0.001）。所有这些趋势主要归因于硫酸盐气溶胶的变化。气溶胶污染极端事件的进一步分析（APEE;定义为每日AOD超过长期本地AOD第90百分位数）显示出积极的趋势（+0.16 +/-0.029 decade- 1），但仍有负向趋势（-0.11 +/- 0.020 decade- 1）;由于硫酸盐气溶胶的增加，印度次大陆在整个期间呈现出积极的趋势（+0.02 +/- 0.004 decade- 1）。在前一个时期，中国东部的APEEs变得更频繁（+3.5 +/-0.53天/月-1 10年-1），而在后一个时期，APEEs变得更频繁（-3.6 +/-0.39天/月-1 10年-1）;在印度次大陆，在整个时期内，APEEs的频率更高（+1.1 +/-0.25天/月-1 10年-1）。与气溶胶光学厚度的变化趋势一致，华东地区晴空辐射在地面呈负变化趋势（-3.2 +/- 0.67 W m- 2 decade- 1），大气中的积极趋势（+1.4 +/-0.68 decade- 1），大气层顶部呈负趋势（-1.8 +/-0.43十年-1）;在后一时期，出现了幅度大得多的相反趋势。在印度次大陆，在整个期间，地面、大气和大气顶部的晴空辐射趋势分别为-1.4 +/- 0.38、+1.7 +/- 0.31和+0.5 +/- 0.16 W m-2decade- 1。比较晴空和全天空条件下的辐射趋势表明，吸收性气溶胶在大气中的辐射收支中占主导地位，现代研究和应用回顾分析第2版（MERRA-2）的气溶胶再分析可能高估了对云的辐射响应。这项研究提供了一个最新的长期趋势的气溶胶及其极端事件和辐射在世界上两个污染严重的地区和结果有重要意义的评估正在进行的清洁空气行动在亚洲的环境和气候影响的分析。
Aerosol pollution is an acute environmental issue in developing countries. Asia has been experiencing rapid changes in anthropogenic aerosols during the past two decades due to fast growth in population and economy. It is still an open question how aerosol loadings, represented by aerosol optical depth (AOD), have evolved in this century, particularly during the past decade when China and India implemented a clean air act aiming to improve air quality. Based on Terra aerosol retrievals and aerosol reanalysis, a change point of AOD trend is detected at 2010 in East China versus a persistent increasing AOD trend in the Indian subcontinent with no detectable change point from 2000 to 2019. In East China, positive AOD trend (+0.11 +/- 0.022 decade- 1) is confirmed from 2000 to 2010 (hereinafter the former period) yet negative trend (-0.26 +/- 0.027 decade- 1) is identified from 2011 to 2019 (hereinafter the later period). In the Indian subcontinent, persistent positive trend (+0.04 +/- 0.001) is detected from 2000 to 2019 (hereinafter the whole period). All of these trends are attributed mainly to changes in sulfate aerosols. Further analysis of the aerosol pollution extreme events (APEE; defined as daily AOD over the long-term local 90th AOD percentile) manifest a positive trend (+0.16 +/- 0.029 decade- 1) of the APEEs' magnitude in East China during the former period yet a negative trend (-0.11 +/- 0.020 decade- 1) during the latter period; the Indian subcontinent demonstrates a positive trend (+0.02 +/- 0.004 decade- 1) during the whole period due to increasing sulfate aerosols. The APEEs have become more frequent (+3.5 +/- 0.53 day month-1 decade- 1) in East China during the former period yet less frequent (-3.6 +/- 0.39 day month-1 decade-1) during the latter period; in the Indian subcontinent, more frequent APEEs (+1.1 +/- 0.25 day month-1 decade- 1) have been detected during the whole period. Consistent with the AOD trends, clear-sky radiation in East China shows a negative trend at the surface (-3.2 +/- 0.67 W m- 2 decade- 1), a positive trend in the atmosphere (+1.4 +/- 0.68 decade- 1), and a negative trend at the top of the atmosphere (-1.8 +/- 0.43 decade- 1) during the former period, respectively; opposite trends with much larger magnitude are seen during the latter period. In the Indian subcontinent, the clear-sky radiation trends during the whole period are -1.4 +/- 0.38, +1.7 +/- 0.31, and + 0.5 +/- 0.16 W m- 2 decade- 1 at the surface, in the atmosphere, and at the top of the atmosphere, respectively. Comparison of radiation trends at clear-sky and all-sky conditions suggests that absorbing aerosols dominate the radiation budget in the atmosphere and the aerosol reanalysis of the Modern-Era Retrospective Analysis for Research ans Applications version 2 (MERRA-2) might overestimate the radiation response to clouds. This study provides an up-to-date analysis of the long-term trends in aerosols and their extreme events and radiation in two of the world's heavily polluted regions and the results have important implications for assessment of the environmental and climatic impacts of the ongoing clean air acts in Asia.