Improvement And Numerical Simulation Of Soil Coupling Model In Common Land Model

The Common Land Model calculates the soil moisture content and the temperature separately.And only considers the effect of temperature on the soil water content when the soil water produces freeze-thaw conditions.Energy gradient is the driving force of soil moisture migration.Under non-isothermal conditions,the energy gradient of soil water includes not only the water potential gradient but also the temperature gradient,and both of them will cause soil moisture migration.The presence of temperature gradient causes the internal moisture in the soil to migrate from the hot end to the cold end,and moisture migration carries heat at the same time.It can be seen that the water heat transfer of the soil influences each other.In this paper,the effect of temperature gradient on soil moisture migration was considered,and the model of soil water heat coupling in vegetation was reestablished.Using the Common Land Model,the equations were discretized with an unconditional stability Crank-Nicolson format,and a numerical simulation experiment was carried out on soil water heat transfer.This paper selects a farmland(E114.3325,N35.0625)in Fengqiu county of Henan province as the research object.A single point numerical simulation experiment was conducted using the data of GLDAS in 2014.By analyzing the simulated values and observed values of soil moisture and temperature in the shallow soil of 0-10 cm,the water-heat coupled model established in this paper is used to simulate the shallow soil temperature and soil water content.The results of data test show that before and after the improvement of the model can simulate the changes of the shallow soil and water content and temperature.The similarity coefficient between the simulated value and the observed value after the improvement is larger than that before the improvement,and the root mean square error is smaller.After comparison,it can be seen that the simulated performance of shallow soil temperature and soil moisture is better after the model improved without the influence of human factors.