CLM在淮河流域数值模拟试验

NUMERICAL SIMULATION OF CLM OVER HUAIHE BASIN

文中利用 1998年HUCEX资料对CommonLandModel(CLM )的模拟能力进行了验证。结果表明 ,CLM不但能够较好地模拟陆 气间各种能量通量 ,而且还能模拟出土壤中温度的时空分布特征。春季 ,CLM对潜热模拟偏高 ,从而引起土壤温度模拟偏低 ;而在夏季 ,潜热模拟偏低 ,在旱地下垫面由于净辐射模拟偏低使土壤温度的模拟仍然偏低 ,水田下垫面的土壤温度模拟趋向合理。夏季的水田无论在对大气的能量输送还是土壤的温度分布上 ,都有其特殊性 ,需在陆面模式中予以特殊的考虑。

The Common Land Model(CLM) is used to simulate the characteristics of exchange of sensible and latent flux and thermodynamic 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 comparison result of simulated and observed data shows that CLM is not only able to simulate basic characteristics 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 at dry form shows that the latent heat flux is underestimated and the sensible heat flux is accordingly overestimated when the turbulence process is strong at noon in both May and August. In May, the latent heat is overestimated and simulated errors vary distinctly with the change of stability of the surface layer atmosphere. In August, the latent heat is always underestimated in varied atmosphere stability. The mean simulated error of latent heat and sensible heat is about 10 W/m2. In both May and August, 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 net solar fluxes in CLM are lower than observation by 10 W/m2 in both May and August. The latent heat flux is usually overestimated in May while it is underestimated in August except that it is overestimated 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 thermodynamic 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.