A group of scientists from the Space Research Institute of the Russian Academy of Sciences, the Institute of Water and Environmental Problems of the SB RAS and the Moscow Institute of Physics and Technology proposed a method for determining the depth of freezing of soil using satellite microwave radiometry.
Permafrost, sea ice, snow and ice, continental ice sheets, mountain glaciers and ice cloud systems are key components of the Earth's cryosphere. Scientific research of the cryosphere is of great importance for solving problems related to climate change, regional water resources, permafrost degradation and sea level change. However, regions with components of the cryosphere, as a rule, are characterized by severe climatic conditions, a large extent and inaccessibility.
Satellite microwave radiometry is the most optimal method of remote sensing, which allows you to explore inaccessible or even previously unknown places on our planet.
“This method has several advantages,” said Vasily Tikhonov, associate professor of space physics at the Moscow Institute of Physics and Technology and senior researcher at the IKI RAS. , sensitivity to subsurface processes, as well as relative cheapness. We checked the accuracy of the method using the example of the Kulundinskaya plain - the vast steppe of the southern part of Western Siberia. For this, a comparative analysis of satellite microwave radiometry data, real soil parameters and climatic characteristics obtained at weather stations was required. ”
It turned out that the same satellite data values can correspond to different depths of soil freezing. This is affected by the ability of the soil to microwave radiation, which may vary depending on moisture, salinity, composition and other characteristics. Scientists also found that single measurements using radiometry can not give accurate results, since radio waves are reflected from the boundaries between the frozen layer and unfrozen soil.
The researchers included this in the calculation and proposed a method by which it is possible to determine the depth of soil freezing according to the SMOS (Soil Moisture and Ocean Salinity) satellite with high accuracy. Remote determination of the freezing depth is based on the joint use of the radiation model developed by the authors, depending on the characteristics of the soil and daily series of remote measurements of thermal radiation. The study period began with the freezing date, which is determined by the satellite as a sharp increase in thermal radiation, and ended with the beginning of thawing - a sharp decrease in thermal radiation.
Model calculations were verified with real measurements on test sites. The obtained dependence is high enough to use the method for reconstructing the depths of soil freezing from satellite data.