Simulated Study On The Characteristics Of Land Surface Process Over The Cold Region

The simulations of land surface model over high latitude and Qinghai-Xizang plateau regions directly impacts on the performance of GCM. In this thesis, the observational data is used as forcing field to investigate the performance of land surface model over Qinghai-Xizang plateau. Influence of different soil moisture initial value and different soil composition are analyzed on the cold land surface process. The main results of this study show as follows:1 .The fetures of cold climate are analyzed firstly by using the observational data of 1998 GAME/Tibet at Shiquanhe, 2002-2003 GAMP/Tibet intensive period(CEOP-EOP3) at Gaize.Then this data was used as forcing data of a land surface model to study the it's performance over Qinghai-Xizang plateau. The simulated result shows that CoLM can reproduced surface thermal and moisture features,the model has a well performance over the Qinghai-Xizang plateau.2.The simulated result have revealed that over western Qinghai-Xizang plateau, the sensible heat fluxes dominate the surface heat energy balance, the latent heat fluxes are less, especially, in frozen season (arid),the latent heat fluxes almost equal to 0. But during of thawing season(wet),at western Qinghai-Xizang Plateau, the latent heat fluxes can't be ignored. When thawing occur, it is also transition period from arid season to rain/wet season(that is latly May), the surface layer soil moisture phase change are frequently happen as result of thawing, these process contribute to the latent heat fluxes. As same time, the Bowen ratio is decreased. The change of surface heat fluxes (sensible and latent heat) is associated with the precipitation and land surface frequent frozen-thaw.3. We examined the impact of initial soil moisture and soil types on model output by running the model with different sets of values for the beginning soil moisture and soil types at each of the ten layers. According to simulation results, the soil moisture test indicated that the initial soil moisture fraction is very important, the initial soil moisture increasing makes the increase of latent heat fluxes. Through analyse influence of 12 different soil types on the cold land surface process, revealed that the assignments of water and energy are sensitive to soil conditions. The soils rich in clay , such as clay and silty clay , have well water - content ability,suface moisture . Because the soil freeze-thaw over the cold region, different soil types during freeze-thaw time sensible heat flux are very different.