Study on Soil Evaporation and Coupling Transmission of Soil Moisture and Heat in Arid Areas

Simulation of soil evaporation and the study on coupling transmission of soil moisture and heat in arid areas are very important in researching water resources utilization,land surface evolution and climate model.In this paper,the models of coupling transmission of soil moisture and heat and topsoil evaporation are derived so as to accurately estimate soil evaporation,soil temperature and soil moisture content in arid areas based on understanding the mechanism of soil evaporation and coupling transmission of soil moisture and heat.In order to compare the simulated results,the models are used to modify the CoLM land surface model.The simulated results of soil evaporation,soil temperature and soil moisture content before and after modifying the CoLM model are compared based on the observation data collected by Heihe Desert Research Station.The conclusions are as follows:(1) Soil evaporation in arid areas can be simulated well if the internal transmission of water vapor in soil is considered in developing soil evaporation model,and the trend of gradual soil evaporation reduction with the gradual drying-up of topsoil can be accurately simulated;(2) At the daytime,the topsoil temperature is high but the deep-soil one is low,so a downward transmission of soil moisture occurs and the soil evaporation is relatively decreased;at night,however,the topsoil temperature is low but the deep-soil one is high,so an upward transmission of soil moisture occurs and the soil evaporation is relatively increased;(3) There is an interaction between the soil moisture and heat transmissions,and the soil temperature can be simulated well if the coupling transmission of soil moisture and heat is considered;(4) The gradual during-up of topsoil in arid areas can be accurately simulated if the effects of coupling transmission of soil moisture and heat and water vapor transmission are considered.