| 摘要: |
| 采用美国NASA发布的TERRA/MODIS和AQUA/MODIS气溶胶光学厚度产品研究2003—2021年粤港澳大湾区气溶胶时空变化特征。结果表明：2003—2021年粤港澳大湾区的月平均气溶胶光学厚度（aerosol optical thickness，AOT）呈轻微下降趋势；最大值和最小值分别出现在2007年3月（约1.186）和2021年11月（约0.226），相差0.960。粤港澳大湾区的多年月平均AOT最大值出现在春季，夏季和秋季次之，最小值出现在冬季。其空间分布特点为佛山和中山的多年月平均AOT最大，并且以此为中心，向四周逐渐减小，12个月的变化范围约为0.147—1.683。粤港澳大湾区AOT在2003—2021年年平均值的空间分布特点与之类似。且在这19 a间，大部分地区AOT的增长量都小于0（即减少）；少数大于0的呈斑点状散布在整个区域，只在惠州最东部较为集中。AOT增长率反映出佛山的下降趋势相对较弱（约−15%），而肇庆北部则非常明显（约−50%）。虽然粤港澳大湾区的气溶胶呈逐年下降趋势，但由于佛山和中山的多年月平均AOT最大，惠州最东部AOT呈现增长态势，这些地区的气溶胶污染需要持续关注和加强治理，从而进一步改善粤港澳大湾区的空气质量。 |
| 关键词: MODIS 气溶胶光学厚度 卫星遥感 变异系数 粤港澳大湾区 |
| DOI：10.7515/JEE222088 |
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| 基金项目:集美大学国家基金培育计划项目（ZP2021019）；福建省自然科学基金项目（2022J01817，2021J01839） |
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| The temporal and spatial variabilities of aerosol optical thickness over the Guangdong-Hong Kong-Macao Greater Bay Area during 2003 — 2021 |
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XIE Jinghan1,, XIAO Zhongyong1, 2*
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1. College of Harbour and Coastal Engineering, Jimei University, Xiamen 361021, China
2. National Geographic Conditions Monitoring Research Center, Jimei University, Xiamen 361021, China
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| Abstract: |
| Background, aim, and scope Aerosols, one of the primary pollutants suspended in the atmosphere, are composed of liquid and solid particulates with diameters ranging from 1 nm to 10 µm. Aerosols can influence climate change by enhancing solar radiation absorption and scattering. In addition, they can cause diseases (e.g., asthma, lung cancer) because they contain toxic substances (e.g., polycyclic aromatic hydrocarbons, microorganisms). Given the effects of aerosols on climate change and human health, monitoring the aerosol optical thickness (AOT), a physical parameter for measuring the aerosol concentration, is of great importance. As the distribution of aerosols is highly influenced by human activities, the present study investigated the temporal and spatial variabilities of AOT over the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), the frontier area of economic development in China, during 2003—2021. Materials and methods The data adopted in this study were the AOT products: radiometrically and geometrically corrected remote sensing images of TERRA/MODIS and AQUA/MODIS: published by NASA, USA. Based on the AOT products, this study improved the spatial resolution of the data by interpolation. Furthermore, monthly and annual mean AOT were calculated to analyze the temporal variabilities. In terms of spatial variabilities of AOT, monthly and annual mean AOT, and the growth and growth rate during 2003—2021, were computed for each pixel. Finally, both temporal and spatial coefficients of variation were acquired to explore the fluctuation of AOT. Results The results showed that the monthly mean AOT declined slightly during 2003—2021. Its maximum and minimum values appeared in March 2007 (about 1.186) and November 2021 (about 0.226), respectively. Moreover, the multi-year monthly mean AOT reached its maximum value in spring and its minimum value in winter. Finally, the multi-year monthly mean AOT presented a bimodal variation; the first peak appeared in April (about 0.880±0.178), and the second peak (about 0.727±0.153) occurred in August. With regard to its spatial distribution, the value decreased from Foshan and Zhongshan, the center of GBA, to the surrounding areas, with the range of 0.147—1.683. The spatial pattern of multi-year (from 2003 to 2021) annual mean AOT was similar to the pattern of multi-year monthly mean AOT. Finally, the AOT difference during 2003—2021 and the AOT percentage difference during 2003—2021 were less than 0 (i.e., decreased) in most areas of GBA; however, small areas of increase were scattered throughout the whole region but only concentrated east of Huizhou. The AOT percentage difference reflected a relatively mild decline in Foshan (about −15%) and an obvious decline in northern Zhaoqing (about −50%). Discussion The decline of annual mean AOT during 2003—2021 indicated that the policies pertaining to the environmental protection of Guangdong Province had taken effect. The seasonal variabilities of AOT can be attributed to the subtropical monsoon climate of the Pearl River Delta (PRD). The air humidity is high in spring and summer, resulting in an increase of aerosol size as a result of absorption of water, which strengthens the extinction effect of the atmosphere. In addition, the transport of dust from the north increased the aerosols in the PRD in spring. These two reasons led to the occurrence of the largest AOT in spring and the second largest in summer. In autumn and winter, the prevailing northerly wind made the air dry and thus the AOT value was small. In terms of the spatial pattern of multi-year monthly mean AOT and multi-year annual mean AOT, the values in Foshan and Zhongshan were the largest. A possible reason for these larger values is that dense industries were located in Foshan, with the ceramics industry being the most representative. The fuel consumed and dust emitted during the ceramic production led to the highest AOT value in Foshan. The AOT values of Shenzhen and Guangzhou, the most highly developed cities, were less than those in Foshan and Zhongshan, possibly because the dominant industry in Shenzhen and Guangzhou was tertiary industry, which released less air pollution than secondary industry. However, given the high intensity of economic activities, dense population, and developed transportation, the pollutants were mainly discharged from the consumption of energy, electricity, and transportation. Huizhou was less developed than other cities in GBA, and the impact of human activities was small, causing its AOT value to be the lowest. In most areas of GBA, the AOT difference during 2003—2021 was less than 0. The possible reason for the obvious decline of AOT is the adjustment of industrial structure. Conclusion The GBA’s annual trending downward AOT indicates that the air quality has improved and that the region’s air governance has had some initial benefits. However, since the AOT in the easternmost part of Huizhou is trending upward and the monthly average AOT in Foshan and Zhongshan has the highest AOT over the years, it is imperative that the aerosol pollution in these areas be continuously monitored and strengthened in order to further improve the air quality in the GBA. Recommendations and perspectives The temporal and spatial variations of aerosol pollution are very complex, and more in-depth research and comprehensive analysis using multi-source data (e.g., ground-based observation and vertical profiles of aerosol distribution in the atmosphere) are needed to reveal the inherent causes and laws of temporal and spatial characteristics. |
| Key words: MODIS aerosol optical thickness satellite remote sensing coefficient of variation Guangdong-Hong Kong-Macao Greater Bay Area |
