Friday, November 13, 2020

The PO.DAAC is pleased to announce the public release of the CYGNSS Level 3 Soil Moisture Version 1.0, representing the first published land-based geophysical dataset derived from CYGNSS. More information regarding the CYGNSS mission and instrumentation is available from PO.DAAC’s mission webpage.

The CYGNSS soil moisture dataset provides daily and sub-daily estimates of surface soil moisture in netCDF-4 format at a 6-hour discretization for most of the subtropics. It was derived from the CYGNSS L1 SDR by investigators at the University Corporation for Atmospheric Research (UCAR) and the University Colorado at Boulder (CU). Their algorithm uses collocated soil moisture retrievals from SMAP to calibrate CYGNSS observations from the same day. For a given location, a linear relationship between the SMAP soil moisture and CYGNSS reflectivity is determined and used to transform all the CYGNSS observations into soil moisture.

Within this dataset are two soil moisture variables that report the volumetric water content in units of cm3/cm3. The variable SM_subdaily includes up to four soil moisture estimates per day, and SM_daily provides a daily average. The time series covers the period from 18 March 2017 to 16 August 2020. The data producers (Chew and Small, 2020) have provided these data as a preliminary release on behalf of the CYGNSS Science Team, and as such, data users are advised to use caution when interpreting these data.

The data, associated documentation, tools and services are described and discoverable via the PO.DAAC data portal.


Citation: CYGNSS. 2020. CYGNSS Level 3 Soil Moisture from UCAR/CU Version 1.0. Ver. 1.0. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at

Reference: Chew, C. C. and E. E. Small. 'Description of the UCAR/CU Soil Moisture Product'. Remote Sens. 2020, 12, 1558.

Related PO.DAAC Animation: CYGNSS Level 3 Soil Moisture from UCAR/CU Version 1.0 (March 2017 and August 2020)

Comments/Questions? Please contact or visit the PO.DAAC Hydrology Forum.