We present an Arctic aerosol optical depth (AOD) climatology and trend analysis for 2003–2019 spring and summertime periods derived from a combination of multi-agency aerosol reanalyses, remote-sensing retrievals, and ground observations. This includes the U.S. Navy Aerosol Analysis and Prediction System ReAnalysis version 1 (NAAPS-RA v1), the NASA Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), and the Copernicus Atmosphere Monitoring Service ReAnalysis (CAMSRA). Spaceborne remote-sensing retrievals of AOD are considered from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Multi-angle Imaging SpectroRadiometer (MISR), and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Ground-based data include sun photometer data from AErosol RObotic NETwork (AERONET) sites and oceanic Maritime Aerosol Network (MAN) measurements. Aerosol reanalysis AODs and spaceborne retrievals show consistent climatological spatial patterns and trends for both spring and summer seasons over the lower Arctic (60–70^∘ N). Consistent AOD trends are also found for the high Arctic (north of 70^∘ N) from reanalyses. The aerosol reanalyses yield more consistent AOD results than climate models, can be verified well with AERONET, and corroborate complementary climatological and trend analysis. Speciated AODs are more variable than total AOD among the three reanalyses and a little more so for March–May (MAM) than for June–August (JJA). Black carbon (BC) AOD in the Arctic comes predominantly from biomass burning (BB) sources in both MAM and JJA, and BB overwhelms anthropogenic sources in JJA for the study period.AOD exhibits a multi-year negative MAM trend and a positive JJA trend in the Arctic during 2003–2019, due to an overall decrease in sulfate/anthropogenic pollution and a significant JJA increase in BB smoke. Interannual Arctic AOD variability is significantly large, driven by fine-mode and, specifically, BB smoke, with both smoke contribution and interannual variation larger in JJA than in MAM. It is recommended that climate models should account for BB emissions and BB interannual variabilities and trends in Arctic climate change studies.

中文翻译：

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来自长期观测和模型再分析的北极春季和夏季气溶胶光学深度基线——第 1 部分：气候学和趋势

我们提出了 2003-2019 年春季和夏季期间的北极气溶胶光学深度 (AOD) 气候学和趋势分析，该分析来自多机构气溶胶再分析、遥感反演和地面观测的组合。这包括美国海军气溶胶分析和预测系统再分析版本 1 (NAAPS-RA v1)、NASA 现代时代研究和应用回顾性分析版本 2 (MERRA-2) 和哥白尼大气监测服务再分析 (CAMSRA) . 中分辨率成像光谱仪 (MODIS)、多角度成像光谱仪 (MISR) 和正交偏振云气溶胶激光雷达 (CALIOP) 考虑了 AOD 的星载遥感反演。地面数据包括来自 AErosol RObotic NETwork (AERONET) 站点的太阳光度计数据和海洋海洋气溶胶网络 (MAN) 测量结果。气溶胶再分析 AOD 和星载反演显示了北极下游春季和夏季一致的气候空间模式和趋势（60-70^∘  N)。^{在北极高地（70 ∘}以北）也发现了一致的 AOD 趋势 N) 来自重新分析。气溶胶再分析产生比气候模型更一致的 AOD 结果，可以用 AERONET 很好地验证，并证实互补的气候和趋势分析。在三项再分析中，特定 AOD 比总 AOD 变化更大，3 月至 5 月 (MAM) 比 6 月至 8 月 (JJA) 变化更大。北极的黑碳 (BC) AOD 主要来自 MAM 和 JJA 中的生物质燃烧 (BB) 来源，并且在研究期间，BB 在 JJA 中压倒了人为来源。AOD 呈现多年负 MAM 趋势和正 JJA 趋势2003-2019 年期间在北极地区，由于硫酸盐/人为污染的总体减少和 BB 烟雾的 JJA 显着增加。北极 AOD 的年际变化非常大，由精细模式驱动，特别是 BB 烟雾，JJA 的烟雾贡献和年际变化均大于 MAM。建议气候模型应考虑北极气候变化研究中的 BB 排放和 BB 年际变化和趋势。