Data

ESA CCI SM v08.1

The latest version v08.1 includes data to December 31^st, 2022. The algorithm has been updated as follows:

The uncertainty estimates obtained through Triple Collocation Analysis and the consequent merging weights are now generated on a seasonal basis. The product uncertainty is now more representative of seasonal errors in soil moisture retrieval.
The barren ground flagging strategy has been changed to a majority decision, where at least 50% + 1 of the observing sensors are needed to raise the flag. The flag is kept optional, i.e., the soil moisture data is not masked.
Temporal break correction, which was provided as a separate experimental product in previous versions, is now included in COMBINED.
The temporal extent of the products is brought up to the end of 2022.

Further information can be found in the documentation. Licensing conditions follow the principles of openness and transparency wherever applicable. All ECV data products resulting from the project are freely accessible.

Downloading the Data

All (current and past) versions of ESA CCI SM data can be downloaded for free and without registration from the CEDA Archive under "data/daily_files".

Using the Data

For information on how to use the product, please read the Product User Guide (PUG). This is also available in the docs folder of the FTP site (from which the data can be downloaded).

The downloadable data is provided in 2D (longitude, latitude) image files representing one day of the record. A package is available in python for reading the data as daily images and converting these images to time series and reading them.

The source code for our python package and installation instructions are available here: https://github.com/TUW-GEO/esa_cci_sm
The package can be installed via pip using "pip install esa_cci_sm"
The documentation for this package is available here: https://esa-cci-sm.readthedocs.io/en/latest/

Any software that can handle CF conform data should be able to import the raw .nc files (e.g. CDO, NCO, QGIS, ArCGIS, Matlab, R, ...). You can also use the GUI software Panoply to view each file.

Known issues

Below is a summary of the reported issues of the ESA CCI SM products:

ESA CCI SM v08.1

For the grid cells (see the smecv_grid package) 2147, 2148, 2149 (Eastern China), and 2334, 2335 (east of Yakutiya), the processing failed to include observations from the Fengyun (3-B/C/D) sensors series. This leads to a spatial discontinuity in the soil moisture uncertainty field (see figure below) and a systematic decrease in coverage in the June 2011 - December 2022 period. However, it does not lead to a substantial discontinuity in the soil moisture field thanks to the many sensors operational in the same period (see figure below).
The sensor values for ASCATA, ASCATB, and ASCATC in the sensor field are all set to 256 (contrary to what stated in the netCDF file attributes).

ESA CCI SM v08.1 soil moisture for the day 2021-8-3, showing no spatial discontinutity around the affected area.

Citing the data

The following citations are compulsory with the use of the dataset:

Gruber, A., Scanlon, T., van der Scalie, R., Wagner, W., Dorigo, W. (2019), Evolution of the ESA CCI Soil Moisture climate data records and their underlying merging methodology, Earth System Science Data, 11, 717-739, https://doi.org/10.5194/essd-11-717-2019.
Dorigo, W.A., Wagner, W., Albergel, C., Albrecht, F., Balsamo, G., Brocca, L., Chung, D., Ertl, M., Forkel, M., Gruber, A., Haas, E., Hamer, P. D., Hirschi, M., Ikonen, J., de Jeu, R., Kidd, R., Lahoz, W., Liu, Y. Y.,Miralles, D., Mistelbauer, T., Nicolai-Shaw, N., Parinussa, R., Pratola, C., Reimer, C., van der Schalie, R., Seneviratne, S. I. Smolander, T., Lecomte, P. (2017). ESA CCI Soil Moisture for improved Earth system understanding: State-of-the art and future directions, Remote Sensing of Environment. https://doi.org/10.1016/j.rse.2017.07.001.
(compulsory with the use of the COMBINED product) Preimesberger, W., Scanlon, T., Su, C. -H., Gruber, A. and Dorigo, W. (2021). Homogenization of Structural Breaks in the Global ESA CCI Soil Moisture Multisatellite Climate Data Record, in IEEE Transactions on Geoscience and Remote Sensing, vol. 59, no. 4, pp. 2845-2862, April 2021, doi: 10.1109/TGRS.2020.3012896.

Further information

If you are interested in previous product versions, please visit the CEDA Archive or send us a request at:

CCI_SM_CONTACT@EODC.EU

Please consider filling in our anonymous survey at this link, requiring only 8-12 minutes to complete.

Your response is invaluable to the ESA CCI Soil Moisture project and we thank you for any time you can dedicate to it.