ESA Soil Moisture Climate Change Initiative (Soil_Moisture_cci): Version 04.5 data collection

Soil Moisture data (version 04.5) from the European Space Agency's (ESA) Soil Moisture Climate Change Initiative (CCI) project. This dataset collection contains three surface soil moisture datasets, alongside ancilliary data products. The ACTIVE and PASSIVE products have been created by fusing satellite scatterometer and radiometer soil moisture products respectively. In the case of the ACTIVE product, these have been derived from AMI-WS and ASCAT satellite instruments and for the PASSIVE product from the satellite instruments SMMR, SSM/I, TMI, AMSR-E, WindSat, AMSR2 and SMOS. The COMBINED product is generated from the Level 2 active and passive instruments..

The homogenized and merged products present a global coverage of surface soil moisture at a spatial resolution of 0.25 degrees. The products are provided as global daily images, in NetCDF-4 classic file format, the PASSIVE and COMBINED products covering the period (yyyy-mm-dd) 1978-11-01 to 2018-12-31 and the ACTIVE product covering 1991-08-05 to 2018-12-31. The soil moisture data for the PASSIVE and the COMBINED product are provided in volumetric units [m3 m-3], while the ACTIVE soil moisture data are expressed in percent of saturation [%]. For information regarding the theoretical and algorithmic base of the datasets, please see the Algorithm Theoretical Baseline Document (ATBD). Other additional documentation and information documentation relating to the datasets can also be found on the CCI Soil Moisture project web site or in the Product Specification Document.

The data set should be cited using the all of the following references:

1. Gruber, A., Scanlon, T., van der Schalie, R., Wagner, W., and Dorigo, W. (2019). Evolution of the ESA CCI Soil Moisture climate data records and their underlying merging methodology, Earth Syst. Sci. Data, 11, 717–739, https://doi.org/10.5194/essd-11-717-2019

2. Dorigo, W.A., Wagner, W., Albergel, C., Albrecht, F., Balsamo, G., Brocca, L., Chung, D., Ertl, M., Forkel, M., Gruber, A., Haas, E., Hamer, D. P. Hirschi, M., Ikonen, J., De Jeu, R. Kidd, R. Lahoz, W., Liu, Y.Y., Miralles, D., Lecomte, P. (2017). ESA CCI Soil Moisture for improved Earth system understanding: State-of-the art and future directions. In Remote Sensing of Environment, 2017, ISSN 0034-4257, https://doi.org/10.1016/j.rse.2017.07.001

3. Gruber, A., Dorigo, W. A., Crow, W., Wagner W. (2017). Triple Collocation-Based Merging of Satellite Soil Moisture Retrievals. IEEE Transactions on Geoscience and Remote Sensing. PP. 1-13. 10.1109/TGRS.2017.2734070

欧洲空间局（European Space Agency, ESA）土壤湿度气候变化倡议（Soil Moisture Climate Change Initiative, CCI）项目产出的土壤湿度数据（版本04.5）。本数据集集合包含三套地表土壤湿度数据集，同时附带辅助数据产品。主动（ACTIVE）与被动（PASSIVE）产品分别通过融合卫星散射计与辐射计土壤湿度产品构建而成。其中主动型产品的数据源自AMI-WS与ASCAT卫星仪器，被动型产品的数据则来自SMMR、SSM/I、TMI、AMSR-E、WindSat、AMSR2及SMOS等卫星仪器。组合（COMBINED）产品则由二级主动与被动仪器数据生成。

经均一化与融合后的产品具备全球覆盖范围，空间分辨率为0.25度。上述产品以全球逐日影像形式提供，采用NetCDF-4 classic文件格式。其中被动型与组合型产品的时间覆盖范围为1978-11-01至2018-12-31（格式为yyyy-mm-dd），主动型产品的覆盖时段为1991-08-05至2018-12-31。被动型与组合型产品的土壤湿度数据以体积单位[m³·m⁻³]提供，而主动型产品的土壤湿度数据则以饱和百分比[%]表示。若需了解本数据集的理论与算法基础，请参阅《算法理论基线文档》（Algorithm Theoretical Baseline Document, ATBD）。与本数据集相关的其他补充文档及说明资料，可在CCI土壤湿度项目官网或《产品规格文档》中获取。

引用本数据集时需使用以下全部参考文献：
1. Gruber, A., Scanlon, T., van der Schalie, R., Wagner, W. 与 Dorigo, W. (2019). ESA CCI土壤湿度气候数据记录及其核心融合方法的演进. 《Earth Syst. Sci. Data》, 11, 717–739. https://doi.org/10.5194/essd-11-717-2019
2. Dorigo, W.A., Wagner, W., Albergel, C., Albrecht, F., Balsamo, G., Brocca, L., Chung, D., Ertl, M., Forkel, M., Gruber, A., Haas, E., Hamer, D. P., Hirschi, M., Ikonen, J., De Jeu, R., Kidd, R., Lahoz, W., Liu, Y.Y., Miralles, D. 与 Lecomte, P. (2017). 用于提升地球系统认知的ESA CCI土壤湿度数据集：研究现状与未来方向. 《Remote Sensing of Environment》, 2017, ISSN 0034-4257. https://doi.org/10.1016/j.rse.2017.07.001
3. Gruber, A., Dorigo, W. A., Crow, W. 与 Wagner, W. (2017). 基于三重交叉验证的卫星土壤湿度反演数据融合方法. 《IEEE Transactions on Geoscience and Remote Sensing》, PP. 1-13. https://doi.org/10.1109/TGRS.2017.2734070