Simulated radiation characteristics of frozen soil surface at typical microwave bands

The freezing phenomenon occurs generally for moist soil at temperature lower than 273 K. The indicator for freezing is the formation of ice crystals in pores of soil due to phase transition of water. Not all liquid water of frozen soil changes into ice because of sorptive attraction from soil particle´s surface. The unfrozen water decreases in the form of exponential function when temperature going down. The phase transition in soil water results in big change of dielectric constant for frozen soil owing to big difference of dielectric constant between liquid water and ice. An improved model is used to calculate the dielectric constant of frozen soil with typical soil textures, initial water constants and temperatures. The AIEM model is used to simulate the emission characteristics of frozen soil surface at C, X, and Ku bands with the calculated dielectric constant as input. The simulation results show that emissivity of frozen soil increases with temperature decreasing, and there is a sharp increasing for emissivity when freezing. The scale of difference mainly depends on initial water content, soil texture and frequency as well. Based on the behaviors of microwave emission of frozen soil with temperature change, a typical one-day temporal simulation was done to show the emissivity of frozen soil along one day´s temperature change. The alternation of freezing and thawing points could be used for change detection of frozen soil parameters with microwave remote sensing.