State Key Laboratory of Remote Sensing Science, College of Global Change and Earth System Science, Beijing Normal University, Beijing, China.
Department of Atmospheric and Oceanic Science, Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA.
Sci Total Environ. 2019 Nov 20;692:879-891. doi: 10.1016/j.scitotenv.2019.07.326. Epub 2019 Jul 20.
The next-generation geostationary meteorological Himawari-8 satellite carrying the Advanced Himawari Imager (AHI) allows frequent observations of the atmosphere, the surface, and oceans every 10 min. With its retrieval algorithms recently updated, Himawari-8/AHI Version 2 Level 2 aerosol products are now available. However, these retrievals have not yet undergone a quality assessment. This study aims to comprehensively validate the official aerosol optical properties derived from Himawari-8/AHI over land and ocean. Aerosol Robotic Network and Sun-Sky Radiometer Observation Network ground-based measurements at 98 stations in the Himawari-domain region are used to validate aerosol optical depth (AOD, or τ) retrievals at 500 nm and Ångström exponent (AE) retrievals at 440-675 nm from the year 2016. The AOD retrievals agree well with surface observations (i.e., from linear regression, slope = 0.876, intercept = 0.076, and correlation coefficient = 0.756) with a mean absolute error and a root-mean-square error of 0.168 and 0.293, respectively. On site and regional scales, large uncertainties are seen, especially in Australia (significant overestimation) and South Asia (significant underestimation). The AOD retrievals can correctly capture daily variations and show the best (worst) performance in summer (spring). The AE performance is poorer on all scales, showing overall underestimations, especially in Australia, Southeast Asia, and China. The data quality of AOD retrievals improves as the vegetation coverage and the AE increases. This suggests that the official aerosol retrieval algorithm still faces great challenges over bright surfaces and under coarse-particle-dominated conditions. In general, approximately 61% and 64% of the AOD matchups meet the newly defined expected errors of [0.330 × τ + 0.024; -0.132 × τ - 0.125] and [0.519 × τ + 0.005; -0.007 × τ - 0.194] determined by ground measurements and aerosol retrievals, respectively. The highly variable accuracy of aerosol retrievals raises a concern about the reliability of the current product under different environmental conditions and underlying surfaces. It also sheds light on what future improvements need implementing to the aerosol retrieval algorithm.
下一代静止气象卫星 Himawari-8 搭载先进 Himawari 成像仪（AHI），可实现每 10 分钟对大气、地表和海洋进行一次观测。随着其检索算法的最新更新，现在可以提供 Himawari-8/AHI 版本 2 第 2 级气溶胶产品。然而，这些检索结果尚未经过质量评估。本研究旨在全面验证来自 Himawari-8/AHI 的官方气溶胶光学特性在陆地和海洋上的准确性。使用位于 Himawari 区域的 98 个站点的气溶胶机器人网络和太阳天空辐射计观测网络的地面测量数据，对 2016 年 500nm 处的气溶胶光学深度（AOD，或 τ）检索结果和 440-675nm 处的 Ångström 指数（AE）检索结果进行验证。AOD 检索结果与地面观测结果吻合较好（即，线性回归斜率为 0.876，截距为 0.076，相关系数为 0.756），平均绝对误差和均方根误差分别为 0.168 和 0.293。在现场和区域尺度上，存在较大的不确定性，尤其是在澳大利亚（显著高估）和南亚（显著低估）。AOD 检索结果可以正确捕捉到日变化，并且在夏季（春季）表现最佳（最差）。AE 的性能在所有尺度上都较差，整体上存在低估，尤其是在澳大利亚、东南亚和中国。随着植被覆盖率和 AE 的增加，AOD 检索结果的质量会提高。这表明官方气溶胶检索算法在明亮表面和粗粒子主导条件下仍面临巨大挑战。总的来说，约有 61%和 64%的 AOD 匹配满足地面测量和气溶胶检索结果分别确定的新定义的预期误差 [0.330×τ+0.024；-0.132×τ-0.125] 和 [0.519×τ+0.005；-0.007×τ-0.194]。气溶胶检索结果的高度可变精度引起了人们对当前产品在不同环境条件和基础表面下可靠性的关注。这也为气溶胶检索算法未来的改进提供了思路。
