Product name: Sentinel-1 Freeze Thaw
Access to data and contact informaton:
Contact person: Juval Cohen (firstname.lastname(at)fmi.fi)
Data access via ftp:
Overview: The Sentinel-1 Freeze/Thaw (F/T) service provides daily morning and evening detections of the F/T state of the soil in Finland. “Daily” and “6-day” products are generated. The daily product shows the morning or the evening detection of one day, while the 6-day mosaic product shows the median of all morning or evening detections over the last 6 days. A near real-time (NRT) product is available up to 8 hours after Sentinel-1 data acquisition and is replaced by a standard product up to 36 hours after data acquisition. The product includes as ancillary information the SMOS L3FT soil F/T product from Finland, as well as the 2m air temperature and snow depth interpolated from the weather station network of the Finnish Meteorological Institute. Data are provided as multi-layer GeoTIFFs and as PNG quicklooks, in the ETRS89 / UTM zone 35N spatial reference system and in a 1 x 1 km spatial resolution. The product start date is September 1st 2020. The product is not generated for the summer periods.
The F/T algorithm first finds the backscatter of the ground surface and the canopy, by applying a forest backscatter model on the SAR observations. The F/T state is then determined by comparing the retrieved backscatter values to empirically predefined reference backscatter values representing frozen and thaw soil conditions. The output product has three categories for the soil state: frozen, uncertain, and thawed, and a flag indicating the presence of wet snow. The wet snow is recognized based on the ground backscatter, air temperature and snow depth information.
The Sentinel-1 F/T service is still in a prototype stage. A Product Specification Document describing the Sentinel-1 F/T datasets can be found in the data dissemination ftp-site (link above). Additional information on the F/T detection algorithm is provided in the publication below.
When using the data for commercial, educational or scientific works and publications, please cite the following publication:
Juval Cohen, Kimmo Rautiainen, Juha Lemmetyinen, Tuomo Smolander, Juho Vehviläinen and Jouni Pulliainen. 2021. Sentinel-1 based soil freeze/thaw estimation in boreal forest environments, Remote Sensing of Environment, Volume 254. DOI: 10.1016/j.rse.2020.112267