Abstract. Ambient fine particulate matter (PM_2.5) is the leading global environmental determinant of mortality. However, large gaps exist in ground-based PM_2.5 monitoring. Satellite remote sensing of aerosol optical depth (AOD) offers information to fill these gaps worldwide, when augmented with a modeled PM_2.5 to AOD relationship (η). This study aims to understand the spatial pattern and driving factors of η from both observations and modeling. A global observational estimate of η for the year 2019 is inferred from 6,118 ground-based PM_2.5 measurement sites and satellite retrieved AOD from the MAIAC algorithm. A global chemical transport model, GEOS-Chem, in its high performance configuration (GCHP), is used to interpret the observed spatial pattern of annual mean η. Measurements and the GCHP simulation consistently identify a global population-weighted mean η of 92 – 100 μg/m³, with regional values ranging from 60.3 μg/m³ for North America to more than 130 μg/m³ in Africa. The highest η is found in arid regions where aerosols are less hygroscopic due to mineral dust, followed by regions strongly influenced by surface aerosol sources. Relatively low η is found over regions distant from strong aerosol sources. The spatial variation of η is strongly influenced by aerosol composition driven by its effects on aerosol hygroscopicity. Sensitivity tests with globally uniform parameters reveal that aerosol composition leads to the strongest η spatial variability, with a population-weighted normalized mean difference of 12.3 μg/m³, higher than that from aerosol vertical profile (8.4 μg/m³), reflecting the determinant composition effects on aerosol hygroscopicity and aerosol optical properties.

中文翻译：

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PM2.5 与 AOD 关系的全球空间变化受气溶胶成分的强烈影响

摘要。环境细颗粒物 (PM _2.5 ) 是全球死亡率的主要环境决定因素。然而，地面 PM _2.5监测存在很大差距。气溶胶光学深度 (AOD) 卫星遥感通过模拟 PM _2.5与 AOD 关系 (η) 提供的信息可填补全球范围内的这些空白。本研究旨在从观测和建模中了解 η 的空间格局和驱动因素。 2019 年 η 的全球观测估计值是根据 6,118 个地面 PM _2.5测量点和卫星从 MAIAC 算法检索的 AOD 推断出来的。全球化学品传输模型 GEOS-Chem 以其高性能配置 (GCHP) 来解释观测到的年平均 η 的空间模式。测量和 GCHP 模拟一致确定全球人口加权平均 η 为 92 – 100 μg/m ³，区域值范围从北美的 60.3 μg/m ³到非洲的超过 130 μg/m ³ 。最高的 η 出现在由于矿物粉尘而气溶胶吸湿性较低的干旱地区，其次是受表面气溶胶源强烈影响的地区。在远离强气溶胶​​源的区域发现相对较低的 η。 η 的空间变化受到气溶胶成分的强烈影响，而气溶胶成分又对气溶胶吸湿性产生影响。全球统一参数的敏感性测试表明，气溶胶成分导致最强的 η 空间变异性，群体加权归一化平均差为 12.3 μg/m ³，高于气溶胶垂直剖面的差值（8.4 μg/m ³），反映了决定性成分对气溶胶吸湿性和气溶胶光学性质的影响。