Two decades of satellite observations of AOD over mainland China using ATSR-2, AATSR and MODIS/Terra: data set evaluation and large-scale patterns
Two decades of satellite observations of AOD over mainland China using ATSR-2, AATSR and MODIS/Terra: data set evaluation and large-scale patterns
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DOI：
10.5194/acp-18-1573-2018
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发表时间：
2018-02-05
影响因子：
6.3
通讯作者：
van der A, Ronald
中科院分区：
文献类型：
--
作者：
de Leeuw, Gerrit;Sogacheva, Larisa;van der A, Ronald
通过卫星观测反演气溶胶特性，可提供无云条件下大面积气溶胶的空间分布。因此，它们补充了地面测量，提供了仪器稀少地区的信息，尽管从卫星和地面观测获得的信息类型和时间信息可能存在重大差异。本文利用不同类型的卫星观测资料，提供了中国大陆气溶胶的三维气候特征，正交偏振云-气溶胶激光雷达（CALIOP）、云-气溶胶激光雷达和红外线探路者卫星观测（CALIPSO）卫星上的激光雷达的消光系数垂直廓线和柱积分消光系数（气溶胶光学厚度- AOD），可从三个辐射计获得：欧洲航天局（ESA）的沿轨扫描辐射计第2版（ATSR-2），先进的沿轨扫描辐射计（AATSR）（统称为ATSR）和美国宇航局的中分辨率成像光谱仪（MODIS）搭载在Terra卫星上，时间跨度为1995-2015年。AOD数据是使用ATSR双视图（ADV）v2.31算法从ATSR中检索的，而对于MODIS Collection 6（C6），AOD数据集是通过合并从暗目标（DT）和深蓝（DB）算法获得的AOD而获得的，进一步称为DTDB合并的AOD产品。这些数据集进行了验证，并使用气溶胶机器人网络（AERONET）版本2 L2.0 AOD数据作为参考进行了差异比较。结果表明，在中国，ATSR略低估了AOD，而MODIS略高估了AOD。结果表明，ATSR的气溶胶光学厚度总体上低于MODIS的气溶胶光学厚度，且随着气溶胶光学厚度的增加，两者的差异逐渐增大。比较还表明，无论是ATSR还是MODIS的AOD数据集，在任何地方都没有一个比另一个更好。然而，ATSR ADV在MODIS DB设计的明亮表面上有局限性。为了将C6与C5.1数据进行比较，本文还简要讨论了中国地区C6和C5.1数据的差异。20年的AOD时间序列，平均在中国大陆，并简要讨论。以17年的ATSR数据为基础，利用MODIS/Terra跟踪近年来环境卫星Envisat丢失时的时间演变，需要对重叠期间的数据集进行比较，以显示其互补性。ATSR先于1995年和2000年之间的MODIS时间序列，并显示在此期间的AOD明显增加。这两个数据系列在2000年至2011年的重叠期间显示出类似的变化，最小值和最大值出现在同一年。中分辨率成像分光仪将这一时间序列延长到2012年环境卫星观测期结束之后，显示出气溶胶光学厚度的下降。
The retrieval of aerosol properties from satellite observations provides their spatial distribution over a wide area in cloud-free conditions. As such, they complement ground-based measurements by providing information over sparsely instrumented areas, albeit that significant differences may exist in both the type of information obtained and the temporal information from satellite and ground-based observations. In this paper, information from different types of satellite-based instruments is used to provide a 3-D climatology of aerosol properties over mainland China, i.e., vertical profiles of extinction coefficients from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), a lidar flying aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite and the columnintegrated extinction (aerosol optical depth - AOD) available from three radiometers: the European Space Agency (ESA)'s Along-Track Scanning Radiometer version 2 (ATSR-2), Advanced Along-Track Scanning Radiometer (AATSR) (together referred to as ATSR) and NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite, together spanning the period 1995-2015. AOD data are retrieved from ATSR using the ATSR dual view (ADV) v2.31 algorithm, while for MODIS Collection 6 (C6) the AOD data set is used that was obtained from merging the AODs obtained from the dark target (DT) and deep blue (DB) algorithms, further referred to as the DTDB merged AOD product. These data sets are validated and differences are compared using Aerosol Robotic Network (AERONET) version 2 L2.0 AOD data as reference. The results show that, over China, ATSR slightly underestimates the AOD and MODIS slightly overestimates the AOD. Consequently, ATSR AOD is overall lower than that from MODIS, and the difference increases with increasing AOD. The comparison also shows that neither of the ATSR and MODIS AOD data sets is better than the other one everywhere. However, ATSR ADV has limitations over bright surfaces which the MODIS DB was designed for. To allow for comparison of MODIS C6 results with previous analyses where MODIS Collection 5.1 (C5.1) data were used, also the difference between the C6 and C5.1 merged DTDB data sets from MODIS/Terra over China is briefly discussed.The AOD data sets show strong seasonal differences and the seasonal features vary with latitude and longitude across China. Two-decadal AOD time series, averaged over all of mainland China, are presented and briefly discussed. Using the 17 years of ATSR data as the basis and MODIS/Terra to follow the temporal evolution in recent years when the environmental satellite Envisat was lost requires a compari son of the data sets for the overlapping period to show their complementarity. ATSR precedes the MODIS time series between 1995 and 2000 and shows a distinct increase in the AOD over this period. The two data series show similar variations during the overlapping period between 2000 and 2011, with minima and maxima in the same years. MODIS extends this time series beyond the end of the Envisat period in 2012, showing decreasing AOD.