| As the most prominent and complicated terrain on the globe,the Tibetan Plateau, with an elevation of more than 4000m on average above mean sea leave makes up approximately one fourth of the land area of China.The plateau surface absorbs a large amount of solar radiation energy,and undergoes dramatic seasonal changes of surface heat and water fluxes.Long-term research on the Tibetan Plateau has shown that the giant prominence exerts thermal effects on the atmosphere,and thus greatly influences atmospheric circulations over China,Asia and even the whole globe.The key to improve the Asian monsoon and global weather and climate forecasting using global general circulation model(GCM) is to better understand the Tibetan Plateau land surface process.GAME/Tibet and follow-up research work made an important contribution to understanding land surface processes.Land surface process affect weather and climate,mainly through the energy,momentum and water vapor exchange between land and air.The land surface heterogeneity results in the heterogeneity of the energy partitioning at the surface,and the characteristics change of surface has a significant impact on the meteorological elements near the surface. Surface temperature plays an important role in the the interactions between the land surface and atmosphere,while the surface temperature depends on the soil heat transfer process,including:thermal conduction and thermal convection.Much attention has been focused on the research of the soil thermal diffusivity and luquid water flux density,associated with the heat exchange,Gao et al(2003) pointed out the the change of soil temperature not only caused by thermal conductivity,but also related to thermal convection,caused by the vertical movement of soil water,They gave the soil thermal conduction-convection equation and solved the analytical solution of the equation.Gao et al(2005,2007) showed the reliability of Gao method the energy point of view.The main purpose of this research is to apply a new soil temperature algorithm coupled thermal conduction and convection,first proposed by GAO et al,to Tibetan Plateau.The soil thermal diffusivity and liquid water flux density in Tibetan Plateau was determined,On the basis of data collected at eight SMTMS sites in 1998 during GAME/Tibet,and the impact of soil water vertical movement on the energy budget at Amduo on the Tibetan Plateau using GAME/Tibetan IOP98 data.The main conclusion are as follows:(1) The soil thermal diffusivity,k=0.17×10-6 m2·s-1～9.78×10-6 m2·s-1,and liquid water flux density,W=-5.66×10-6 m·s-1～3.59×10-5 m·s-1,for Tibetan Plateau using the soil temperature data,at the depth of 0.04m and 0.20m,collected at eight SMTMS sites in 1998 during GAME/Tibet;On averag(?),soil thermal diffusivity,from small to big in the following order:Tuotuohe＜Amdo＜Noda＜Ms3608＜Wadd＜D66＜D110＜Ms3637,while liquid water flux density is:Tuotuohe＜D110＜Noda＜Amdo＜D66＜Wadd＜Ms3608＜Ms3637,The Tuotuohe station's values are the smallest,the Ms3637 station's values are the largest;The eight station can be divided into three categories according its value changes,Tuotuohe,Amdo,Noda and Ms3608's values are smaller,while Ms3637 and D110's values are larger,D66 and Wadd's values are between them;General speaking,soil thermal diffusivity and liquid water flux density don't change with volumetric soil water content(θ),but when volumetric soil water content is at the smaller value,both soil thermal diffusivity and liquid water flux density decrease with increasing volumetric soil water content; Conclusion in June coincides with concluded in the entire time period.(2) The soil thermal diffusivity,k=0.07×10-6 m2·s-1～2.20×10-6 m2·s-1,and liquid water flux density,W=-2.72×10-6 m·s-1～2.53×10-5 m·s-1,for Amduo using the soil temperature data,at the depth of 0.05m,0.10m and 0.20m,collected at Amduo PBL station in 1998 during GAME/Tibet;On average,soil thermal diffusivity first decrease just below the surface then dramatically increase,while liquid water flux density decrease with increasing soil depth,Both soil thermal diffusivity and liquid water flux density are vertical heterogeneity,which reflects the differences in soil thermodynamic characteristics and heterogeneity of soil thermal properties in different depth of soil layers;Both the value at peak probability of soil thermal diffusivity and liquid water flux density distribution,and the emergence probability of W＜0 increase with increasing depth;The distribution of soil thermal diffusivity and liquid water flux density at 0.125m depth as one of the middle layer,its distribution is different from the shallow and deep,which make more gradient of soil surface temperature observations necessary to research of soil thermal properties; General speaking,soil thermal diffusivity and liquid water flux density don't change with volumetric soil water content(θ),but when volumetric soil water content ranges from 10%to 25%,both soil thermal diffusivity and liquid water flux density decrease with increasing volumetric soil water content;Conclusion in PBL station coincides with concluded in the SMTMS station.(3)The energy budget closure for the traditional method and the Gao method is respectively 0.53 and 0.72,which show the heat transfer caused by the vertical movement of soil liquid water is very important to the research of soil thermal property.
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