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Interdecadal Changes in Aerosol Optical Depth Over Pakistan Based on the MERRA-2 Reanalysis Data During 1980–2018
Remote Sensing ( IF 5 ) Pub Date : 2021-02-23 , DOI: 10.3390/rs13040822
Rehana Khan , Kanike Raghavendra Kumar , Tianliang Zhao , Waheed Ullah , Gerrit de Leeuw

The spatiotemporal evolution and trends in aerosol optical depth (AOD) over environmentally distinct regions in Pakistan are investigated for the period 1980–2018. The AOD data for this period was obtained from the Modern-era retrospective analysis for research and applications, version 2 (MERRA-2) reanalysis atmospheric products, together with the Moderate-resolution imaging spectroradiometer (MODIS) retrievals. The climatology of AODMERRA-2 is analyzed in three different contexts: the entire study domain (Pakistan), six regions within the domain, and 12 cities chosen from the entire study domain. The time-series analysis of the MODIS and MERRA-2 AOD data shows similar patterns in individual cities. The AOD and its seasonality vary strongly across Pakistan, with the lowest (0.05 ± 0.04) and highest (0.40 ± 0.06) in the autumn and summer seasons over the desert and the coastal regions, respectively. During the study period, the annual AOD trend increased between 0.002 and 0.012 year-1. The increase of AOD is attributed to an increase in population and emissions from natural and/or anthropogenic sources. A general increase in the annual AOD over the central to lower Indus Basin is ascribed to the large contribution of dust particles from the desert. During winter and spring, a significant decrease in the AOD was observed in the northern regions of Pakistan. The MERRA-2 and MODIS trends (2002–2018) were compared, and the results show visible differences between the AOD datasets due to theuseof different versions and collection methods. Overall, the present study provides insight into the regional differences of AOD and its trends with the pronounced seasonal behavior across Pakistan.

中文翻译:

基于MERRA-2再分析数据的1980-2018年巴基斯坦气溶胶光学厚度的年代际变化

研究了1980-2018年期间巴基斯坦不同环境区域的气溶胶光学深度(AOD)的时空演变和趋势。这一时期的AOD数据是从现代时代的研究和应用回顾性分析(版本2(MERRA-2)再分析大气产品)以及中等分辨率成像光谱仪(MODIS)检索中获得的。AOD MERRA-2的气候在三种不同的情况下进行分析:整个研究领域(巴基斯坦),该领域内的六个地区以及从整个研究领域中选择的12个城市。MODIS和MERRA-2 AOD数据的时间序列分析显示了各个城市的相似模式。巴基斯坦的AOD及其季节性变化很大,在沙漠和沿海地区的秋季和夏季分别最低(0.05±0.04)和最高(0.40±0.06)。在研究期间,每年的AOD趋势0.002 0.012年期间增加-1。AOD的增加归因于人口和自然和/或人为来源的排放增加。中部至印度河下游地区的年度AOD普遍增加归因于沙漠中尘埃颗粒的大量贡献。在冬季和春季,巴基斯坦北部地区的AOD明显下降。比较了MERRA-2和MODIS趋势(2002-2018年),结果表明由于使用了不同的版本和收集方法,AOD数据集之间存在明显的差异。总体而言,本研究提供了对AOD区域差异及其趋势以及巴基斯坦各地明显的季节性行为的见解。
更新日期:2021-02-23
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