The Sentinel-1 Global Backscatter Model extension over the polar zones and sea ice regions.

Abstract

With the recently published Sentinel-1 Global Backscatter Model (S1GBM) Version 1.0 [ref 1, 2], we provide a new perspective on Earth’s land surface through normalised microwave backscatter maps from Sentinel-1’s Synthetic Aperture Radar (SAR) observations. The S1GBM V1.0 describes Earth’s land surface for the period 2016–17 by the mean C-band radar cross section in VV- and VH-polarisation at a 10 m sampling, giving a high-quality impression on surface- structures and -patterns. Supporting not only the design and verification of upcoming radar sensors (including Sentinel-1C), the obtained S1GBM data also serve land cover classification and determination of vegetation and soil states, as well as water body mapping.

In the course of its generation, we processed 0.5 million Sentinel-1 scenes totalling 1.1 PB, and performed semi-automatic quality curation and backscatter harmonisation related to orbit geometry effects. S1GBM V1.0 comprises land observations from Sentinel-1’s Interferometric Wide (IW) swath mode in VV- and VH-polarisation, collecting Ground-Range-Detected data at High-resolution (GRDH) from the full 2016-2017 period. The overall mosaic quality excels (the few) existing datasets, with minimised imprinting from orbit discontinuities and successful angle normalisation in large parts of the world. Hosted at our institutional data repository [ref 3] following the FAIR principles, we provide under open license the VV and VH mosaic as tiles that are organised in a folder structure for six continents (omitting non-covered Antarctica). With this, twelve zipped dataset-collections per continent are available for download [ref 4].

In this conference contribution, we present the first extension of the S1GBM, V1.1, providing an additional set of normalised mosaics covering the northern and southern polar zones and sea ice regions. V1.1 ingests Medium-resolution data (GRDM) from Sentinel 1’s Extra Wide (EW) swath mode in HV- and HH-polarisation, at a pixel sampling of 40m. To reflect cold and warm conditions in the high latitudes, and in particular to capture the varying snow pack extents along Greenland’s coastline, data collections are set to the months January and July of the period 2016-17, respectively. Processing, normalisation- and mosaicking methods, and publication terms follow with minor adaptions the existing V1.0 dataset publication.

This extension of the S1GBM allows the characterisation of the Earth’s land surface in 2016-17 by the mean C-band radar cross section, now also including the Arctic and the Antarctic coastline and the polar sea ice regions, which are of particular interest of when mapping climate change impacts.

References [ref 1] https://www.nature.com/articles/s41597-021-01059-7 [ref 2] https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-1/sentinel-1-global-backscatter-model [ref 3] https://researchdata.tuwien.ac.at [ref 4] https://doi.org/10.48436/n2d1v-gqb91