ESA CCI SM SUB-DAILY Long-term Climate Data Record of sub-daily Soil Moisture from merged multi-satellite observations

This dataset was produced with funding from the European Space Agency (ESA) Climate Change Initiative (CCI) Plus Soil Moisture (SM) Project (CCN 4 to ESRIN Contract No: 4000126684/19/I-NB "ESA CCI+ Phase 1 New R&D on CCI ECVS Soil Moisture").  Project website: https://climate.esa.int/en/projects/soil-moisture/

This dataset contains information on the Surface Soil Moisture content derived from satellite observations in the microwave domain.

The operational (ACTIVE, PASSIVE, COMBINED) ESA CCI SM products are available at https://catalogue.ceda.ac.uk/uuid/c256fcfeef24460ca6eb14bf0fe09572/ (Dorigo et al., 2017; Gruber et al., 2019; Preimesberger et al., 2021).

Abstract

The ESA CCI SUB-DAILYSM science product is a 12-hourly product that is produced with the same method as the daily ESA CCI COMBINED SM product. For the Sub Daily product, the input data is temporally resampled to 12 hours instead of 24 hours. The temporal window is centred around 0 UTC and 12 UTC. Satellite observations that were taken directly on the border between the two time windows will be added to the previous timestamp to avoid double binning. So observations taken at 6 UTC will be added to 0 UTC, and observations at 18 UTC will be added to 12 UTC.

Due to the increased need for temporal coverage for a subdaily product, it has been produced from 2012 on, after the activation of ASCAT-B and AMSR2. The following Sensors are included in the SUB-DAILY product: ASCAT A, ASCAT B, ASCAT C, AMSR2, FY3b, FY3c, FY3d, GPM, SMAP, SMOS and TRMM.

Programmatic (bulk) download

You can use command-line tools such as wget or curl to download (and extract) data for multiple years. The following command will download and extract the complete data set to the local directory ~/Download on Linux or macOS systems.

#!/bin/bash

# Set download directory
DOWNLOAD_DIR=~/Downloads

base_url="https://researchdata.tuwien.at/records/939n8-zg244/files"

# Loop through years 2012 to 2024 and download & extract data
for year in {2012..2024}; do
    echo "Downloading $year.zip..."
    wget -q -P "$DOWNLOAD_DIR" "$base_url/$year.zip"
    unzip -o "$DOWNLOAD_DIR/$year.zip" -d $DOWNLOAD_DIR
    rm "$DOWNLOAD_DIR/$year.zip"
done

Data details

Data Variables

Each netCDF file contains 3 coordinate variables

• lon: longitude (WGS84), [-180,180] degree W/E
• lat: latitude (WGS84), [-90,90] degree N/S
• time: float, datetime encoded as "number of days since 1970-01-01 00:00:00 UTC"

 and the following data variables

• sm: (float) The Soil Moisture variable reflects estimates of daily average volumetric soil moisture content (m3/m3) in the soil surface layer (~0-5 cm) over a grid cell (0.25 degree).
• sm_uncertainty: (float) The Soil Moisture Uncertainty variable reflects the uncertainty (random error) of the original satellite observations. Derived using triple collocation analysis.
• dnflag: (int) Indicator for satellite orbit(s) used in the retrieval (day/night time). 1=day, 2=night, 3=both
• flag: (int) Indicator for data quality / missing data indicator. For more details, see netcdf attributes.
• freqbandID: (int) Indicator for frequency band(s) used in the retrieval. For more details, see netcdf attributes.
• mode: (int) Indicator for satellite orbit(s) used in the retrieval (ascending, descending)
• sensor: (int) Indicator for satellite sensor(s) used in the retrieval. For more details, see netcdf attributes.
• t0: (float) Representative time stamp, based on overpass times of all merged satellites.

Additional information for each variable are given in the netCDF attributes.

Version Changelog

• Version 9.2 is the first release of this product

Software to open netCDF files

These data can be read by any software that supports Climate and Forecast (CF) conform metadata standards for netCDF files, such as:

• Xarray (Python)
• netCDF4 (Python)
• esa_cci_sm (Python)
• Similar tools exist for other programming languages (Matlab, R, etc.)
• Software packages and GIS tools can open netCDF files, e.g. CDO, NCO, QGIS, ArcGIS
• You can also use the GUI software Panoply to view the contents of each file

Related Records

This record and all related records are part of the ESA CCI Soil Moisture science data records community.