NUMERICAL SIMULATION OF CLM OVER HUAIHE BASIN

The Common Land Model(CLM) is used to simulate the characteristics of exchange of sensible and latent flux and thermody namic process in soil,and validate the simulation of CLM on two underlying surfaces,dry farm and paddy field,in two vegetative seasons,May and August,over Huaihe River basin using the data of HUBEX/GAME in 1998.The com parison result of simulated and observed data shows that CLM is not only able to simulate basic charact eristics of energy and mass transfer between land and air,but also able to simulate the heat transfer in soil.The study concludes that:(1) The simulation atdry form shows that the latentheat flux is underest imated and the sensible heat flux is accordingly overest imated when the turbulence process is strong at noon in both May and August.In May,the lat entheat is overestimated and simulated errors vary distinctly with the change of stability of the surface layer at mosphere.In August,the latentheat is always underest imated in varied atmosphere stability.The mean simulated error of latentheat and sensible heat is about 10 W/m2.In both May and Aug ust,the simulated soil temperatures are lower than observation and there is one-hour late in phase difference.(2) The simulation at paddy field shows that the simulated netsolar fluxes in CLM are lower than observation by 10 W/m2 in both May and August.The latentheat flux is usually overest imated in May while it is underest imated in August except that it is overest imated when turbulence transfer is strong.The simulated soil temperatures in August are plausible and in accordance with the observed data from both the daily variation in phase and range of temperature variation.Compared with May,the simulation of thermody namic process in soil is greatly improved.(3) The comparison results of four simulating experiments show that the simulation of CLM is,to great extend,influenced by the choice of underlying surface types and the characteristics of water and heat transfer in soil.So it is necessary to identify precisely the parameters of underlying surfaces when CLM is applied.