GF-5 EMI观测新冠疫情期间全球典型地区NO_(2)柱浓度变化

Tropospheric NO_(2) changes in global typical regions during the COVID-19 pandemic from GF-5 EMI observations

中国“高分五号”(GF-5)卫星上搭载的痕量气体差分吸收光谱仪(EMI)是第一台设计用于大气痕量气体的探测的高光谱载荷。本文首次基于EMI NO_(2)观测结果分析全球NO_(2)污染典型区域在新冠疫情期间的NO_(2)浓度变化情况。结果表明EMI载荷捕捉到了2020年1—3月,中国东部(-13.6%)、欧洲(-10.2%)、伊朗(-7.9%)和韩国(-13%)等大部分地区NO_(2)柱浓度区域均值的明显下降趋势。不论是同年封锁前后的比较,还是2020年封锁期间与2019年同期的比较,都能够看到EMI NO_(2)柱浓度明显的下降。NO_(2)柱浓度下降的主要原因是疫情期间采取的限制性措施导致的交通和工业活动排放大幅减少。EMI NO_(2)观测结果与国际同类成熟载荷OMI和TROPOMI观测结果的相关性大于0.97,在区域和城市尺度上EMI与OMI和TROPOMI的平均相对差异分别小于13%和9%。本研究结果体现了EMI在全球NO_(2)污染变化监测的能力和实际应用价值,为中国后续痕量气体探测载荷的研制和应用提供参考。

The novel coronavirus(COVID-19)has been declared a global pandemic in December 2019.To curb the spread of the virus,countries and regions around the world have adopted lockdown measures,which resulted in sharp reductions in their social and economic activities and significantly reduced the concentration of pollutants in their atmosphere.The environmental trace gases monitoring instrument(EMI)onboard the Chinese GaoFen-5(GF-5)satellite is the first hyperspectral sensor designed for monitoring atmospheric trace gases.This study analyzed the tropospheric nitrogen dioxide(NO_(2))changes in typical global areas during the COVID-19 pandemic based on EMI NO_(2) observations.To evaluate the application potential of EMI NO_(2),this study compared the emission reductions monitored by EMI NO_(2) with that monitored by OMI and TROPOMI NO_(2) products.Eastern China,Europe,Iran,and South Korea were selected as the main research areas.The study period covered January 1 to March 31 in 2019 and 2020 and was divided into multiple sub-windows according to the differences in the outbreak and lockdown times in these regions.The comparison of regional-time-averaged EMI NO_(2) in 2019 and 2020 reveals that the EMI captured obvious NO_(2) reduction trends in most areas of Eastern China(−13.6%),Europe(−10.2%),Iran(−7.9%),and South Korea(−13%)from January 1 to March 24.The average relative deviation of EMI NO_(2) reduction percentage from OMI and TROPOMI is less than 12.3%in Eastern China and 13%in Europe.The EMI NO_(2) significantly decreased before and after lockdowns in the same year or in the same period between these two years.To further evaluate the quantitative expression ability of EMI in urban-scale NO_(2) emission reduction,the emission reductions of EMI NO_(2) in several typical cities were calculated and compared with OMI and TROPOMI.The NO_(2) reductions from EMI are highly consistent with those from OMI and TROPOMI.The averaged relative differences between EMI and OMI(TROPOMI)in the regional and urban scales are less than 13%and 9%,respectively.In addition to GF-5,the hyperspectral observation satellite(GF-5B)launched on September 7,2021 and the atmospheric environment monitoring satellite(DQ1)launched on April 16,2022 are also equipped with an EMI sensor.Preliminary results show that these satellites have good data quality and a detection capability comparable with that of GF-5(01)EMI.Other satellites that are planned to be launched,such as high-precision greenhouse gas detection satellite(DQ2)and GF-5 replacement satellite(GF501A),will also be equipped with an EMI sensor to continue monitoring polluting gases in the world and to provide a new source of data for global pollution monitoring.This study assesses the ability and practical application value of EMI in global NO_(2) monitoring and provides a reference for the development and application of similar instruments.