Terrestrial Freeze-thaw Monitoring on the Tibet Plateau Using Passive Microwave Remote Sensing

The terrestrial cryosphere comprises cold areas of Earth’s land surface where water is either permanently or seasonally frozen. This includes most regions north of 40 degrees North latitude and most mountainous regions where elevation is greater than 1000m [1]. Permafrost is ground that perennially at or below 0 throughout the year. Above the permafrost is the active layer, which experiences summer thawing. Approximately 50 million km of the terrestrial Northern Hemisphere undergoes seasonal freeze-thaw transitions each year [2]. Freeze/thaw transitions influence the thermal and hydraulic properties of the soil, which in turn have a significant impact on the surface energy and moisture balance, hence on weather and climate [3]. The distinct changes of surface dielectric properties are occur as water transitions between solid and liquid phases. Radiobrightnesses at frequencies near the Debye relaxation frequency of liquid water are spectrally sensitive to liquid moisture in surface soils and to scatter darkening in frozen soils [4]. Microwave remote sensing is capable of detecting and monitoring terrestrial freeze-thaw processes. Permafrost and seasonally frozen soils occupy two-thirds of the Chinese terrestrial area. The Tibetan Plateau contains one of the highest and largest permafrost areas in Earth’s mid-latitudes. It’s aerodynamic and thermodynamic effects play an important role in regional and global climate [5]. In this paper we try to monitoring terrestrial freeze-thaw states in the Tibet Plateau by using passive microwave brightness temperature from Advanced Microwave Scanning Radiometer Earth Observing System (AMSR-E).