Atomospheric energy and water cycle of Tibetan Plateau

在大气湍流测量的基础上，采用涡旋相关法直接测量了大气与地表界面的感热和潜热交换。在眼压测量过程中，设置了AMDO、MS3478、BJ(NaQu)和MS3637四个流动点并进行了测量。在这些地点还测量了辐射收支、土壤表面温度、土壤温度剖面、土壤水分剖面和土壤热通量。这些测量结果为研究陆面-大气相互作用提供了一个一致的数据库。结果表明，在获得最长和连续数据的安多，感热和潜热通量的日变化和季节变化都很明显。季风来临前，地面非常干燥，地表温度的日变化最大可达50摄氏度。季风…爆发后，由于地面变湿，潜热通量很小，感热通量占主导地位。氮素越多，潜热通量越大，感热通量越小。这种变化与地表温度的下降是一致的。季风前期、季风中期和季风后期也得到了典型的通量日变化(Ishikawa等人，1999年)。Tsukamoto等人(2001)比较了四个站点的通量观测结果。它们还表明，感热通量控制混合层深度的发展。(2001a，2001c)，宫崎骏等人。(2001)，Wang(2001)和Kim等人。(2001)报告的流通量平衡‘。他们认为，造成这种失衡的原因有很多。他们还强调了气团平均垂直运动的重要性，这可能是由小范围有组织的扰动引起的。Tanaka等人。(2001c)对土壤热通量的测量进行了讨论。他们使用土壤水分和温度数据，粗略估计了从4月到6月融化永久冻土和加热土层所需的表层土壤热通量。所需地表热流密度平均约为30W/m~2，高于土壤热板测定值。Tanaka等人。(2001b)对热板的性能进行了数值检验，并建议对土壤热流进行一些修正。表面不平衡问题尚未得到解决。这严重限制了观测通量数据的有用性。西藏西部是一个气象站分布非常稀疏的地区。在改泽和石川河建立了两个自动气象站，并对表层边界层和一些土壤变量进行了连续测量。Haginoya(2001)报告了用鲍文比法估计的这些站点的地面气象和通量。Xu和Haginoya(2001)利用常规地面观测数据估算了14个藏区站点的月平均地表通量。在安多现场，在IOP后继续进行PBL塔观测。Tanaka等人。(2001d)通过将塔台资料与IOP期间的湍流通量进行比较，计算了现场感热通量的整体输送系数。该系数是作为整体理查森数的函数得到的。利用这个系数和连续的塔架观测数据，他们计算了到2000年7月为止的感热通量。年际变化很强，即使是在感热通量最大的春季，塔台观测也失败了。较少

The exchange of sensible and latent heat at the interface of atmosphere and the land surface was directly measured by eddy correlation method based on the measurement of atmospheric turbulence. Four flux sites, Amdo, MS3478, BJ(Naqu) and MS3637, were set up and the measurements were conducted during the IOP. In these sites the radiation budget, soil surface temperature, soil temperature profile, soil moisture profile and soil heat flux were also measured. These measured results serve as a consistent database to study land surface-atmosphere interaction.With this results both diurnal and seasonal changes of the sensible and latent heat flux were clearly detected at Amdo where the longest and continuous data was obtained. Before the monsoon the ground surface was very dry and the diurnal change of the surface temperature was as large as 50 degree Celsius. The latent heat flux was very small and the sensible heat flux was dominant As the ground surface became wet after the onset of monsoo … More n, the latent heat flux increased and the sensible heat flux decreased. This change was in harmony with the decease of the ground surface temperature. Typical diurnal change of fluxes was also obtained for pre-monsoon, mid-monsoon and late-monsoon periods (Ishikawa et al, 1999). Tsukamoto et al(2001) compared the flux observation at four sites. They also show that the sensible heat flux controls the development of the depth of mixing layer.At these flux sites, Tanaka et al. (2001a, 2001c), Miyazaki et al. (2001), Wang (2001) and Kim et al. (2001) reported fluximbalance'. They suggest that many factors are responsible for the imbalance. They also stress the importance of mean vertical motion of air mass which may be induced by small scale organized disturbances. Tanaka et al. (2001c) give a discussion on the measurement of soil heat flux. They roughly estimated the surface soil heat flux needed to melt the permafrost and to heat the soil layer from April to June using the soil moisture and temperature data. The required surface heat flux was about 30W/m^2 on average, which was greater than that measured by soil heat plate. Tanaka et al. (2001b) examined the performance of a heat plate numerically and suggested that some correction is necessary to the soil heat flux. The surface imbalance problem has not yet been resolved. This severely limits the usefulness of the observed flux data.The western Tibet is a region where the distribution of meteorological station is very sparse. Two automated meteorological stations were set up at Gaize and Shichuanhe and the continuous measurement of surface boundary layer and some soil variables has been conducted. Haginoya(2001) reported the surface meteorology and fluxes estimated by the Bowen ratio method at these sites. Xu and Haginoya(2001) estimated the monthly averaged surface fluxes at fourteen Tibetan sites using conventional surface observation data. At Amdo site PBL tower observation has been continued after the IOP. Tanaka et al. (2001d) compute the bulk transfer coefficient for the sensible heat flux at the site by comparing the tower data with turbulent flux during IOP. The coefficient is obtained as a function of the bulk Richardson number. With this coefficient and the continued tower observation data they computed the sensible heat flux until July 2000. The data suggests the strong inter annual variation, even the tower observation failed in Spring, when the sensible heat flux is largest in the year. Less