Water and heat transport in the desert soil and atmospheric boundary layer in western China

In order to understand the exchange and transfer processes of water and energy in the desert soil and the atmospheric boundary layer (ABL), we have developed a coupled model, in which a desert soil model including water movement of both liquid and vapour phase, and an ABL model based on a non-local transilient turbulence closure scheme, are coupled together. With this model, the evolution of potential temperature and specific humidity, the distribution of net radiation among sensible, latent and soil heat fluxes, and the water and heat flux profiles both in the soil and ABL have been simulated. The HEIFE (HEIhe River Basin Field Experiment) observational data are used to calibrate calculation of the water and heat flux both in the soil and the ABL. The sensible and latent heat fluxes warm and moisten the bottom grid box (100 m) of the ABL. In this way the ABL model and the desert soil model are coupled together. The simulated results show that when the flux of water vapour in the soil is neglected, the evaporation rate and the flux profiles of specific humidity in the ABL show great changes, hence the importance of water vapour movement in the desert soil for the calculation of specific humidity in the ABL. In the upper 5 cm of the soil, which is called an active layer, water and heat transport are more effective than in the substrate (soil below 5 cm).