Cai Ying, Irie Hitoshi, Damiani Alessandro, Itahashi Syuichi, Takemura Toshihiko, Khatri Pradeep
Center for Environmental Remote Sensing (CEReS), Chiba University, Chiba, Chiba 263-8522, Japan.
Center for Environmental Remote Sensing (CEReS), Chiba University, Chiba, Chiba 263-8522, Japan.
Sci Total Environ. 2024 Aug 20;939:173490. doi: 10.1016/j.scitotenv.2024.173490. Epub 2024 May 23.
Long-term aerosol optical depth (AOD) datasets focused on the Pacific Ocean in the downwind area of China over a 19-year period from 2003 to 2021 were derived from satellite observations, reanalysis datasets, and numerical simulations. Considering the significant year-to-year changes in the amounts of aerosols transported from China to the Pacific Ocean during this period, we proposed a metric named R. This is defined as the AOD over the ocean relative to that near the eastern coast of China within the same latitude band (25-30°N). R was identified as a valuable metric for quantifying the long-term changes in transboundary air pollution pathways. Our analysis revealed a clear exponential decrease in R values from China toward the Pacific Ocean; this was consistent with the prevailing meteorological conditions observed over the 19-year period. However, the possible long-term changes in R due to climate change were found to be insignificant and were overshadowed by much larger year-to-year variations in the meteorological field. Additionally, significant seasonal variations in the absolute slope of the linear regression between R and longitude were observed, and there correlated with wind patterns in the lower troposphere. Elevated slope values in the spring and winter suggested a west-to-east aerosol transport facilitated by strong winds, whereas the lower slope values in summer and autumn indicated a northward aerosol movement under weaker winds. In recent years, aerosols have become less likely to be transported far eastward from the coast of China. Based on these findings, to enhance the detectability of the climate change impacts on meteorological field affecting transboundary air pollution pathways, the R metric derived using a continued long-term satellite observation of aerosols is proposed.
2003年至2021年的19年间，基于卫星观测、再分析数据集和数值模拟，获取了聚焦于中国下风区太平洋的长期气溶胶光学厚度（AOD）数据集。考虑到这一时期从中国输送到太平洋的气溶胶量存在显著的逐年变化，我们提出了一个名为R的指标。它被定义为同一纬度带（北纬25 - 30°）内海洋上空的AOD与中国东海岸附近的AOD之比。R被确定为量化跨界空气污染路径长期变化的一个有价值的指标。我们的分析表明，从中国向太平洋方向，R值呈明显的指数下降；这与19年期间观测到的主要气象条件一致。然而，气候变化导致的R值可能的长期变化被发现并不显著，并且被气象场中更大的逐年变化所掩盖。此外，还观测到R与经度之间线性回归的绝对斜率存在显著的季节变化，且与对流层低层的风型相关。春季和冬季较高的斜率值表明强风促进了气溶胶从西向东的输送，而夏季和秋季较低的斜率值表明在较弱风力下气溶胶向北移动。近年来，气溶胶从中国海岸向东远距离输送的可能性降低。基于这些发现，为了提高对气候变化对影响跨界空气污染路径的气象场的影响的可探测性，建议使用对气溶胶的持续长期卫星观测得出R指标。
