Identification of Frozen/Thawed Soils in the Areas of Anadyr (Chukotka) and Belaya Gora (Sakha) from the Sentinel 1 Radar Data

Abstract

This paper is focused on the problem of distinguishing between thawed and frozen soils in the 5-cm upper layer at meteorological stations of Belaya Gora (Sakha) (68.5° N) and Anadyr (Chukotka) (64.78° N) with the use of the Sentinel 1 C‑band radar data for the period of 2014–2016. The state of a frozen soil is determined in three ways: (i) by a significant difference (3–5 dB) in the backscattering coefficient σ⁰ (BSC) during the transition of a soil between frozen and thawed states observed in multitemporal radar data, (ii) by a threshold value of \(\sigma _{{{\text{threshold}}}}^{0}\) at which the temperature in the upper soil layer falls below 0°С, and (iii) by textural features for one-channel images. Diagrams of the air-freezing index (AFI) and its trend for the 2012–2018 period have been constructed from the archive data containing the air temperature for the study areas.