陇东黄土高原下垫面不均匀性指标的建立及其对大孔径闪烁仪(LAS)观测感热通量的影响

目前定量研究下垫面不均匀性对大孔径闪烁仪(LAS)、涡动相关仪(ECS)观测感热通量差异的影响还比较少.本文利用黄土高原庆阳观测站2012年6、7月典型晴天两主风向范围E-SE和SW-W的陆面过程数据,在建立了下垫面不均匀性定量化指标的基础上,分析了下垫面不均匀性与地表温度变率的关系及其对LAS、ECS观测感热通量差异的影响.结果表明:庆阳站下垫面不均匀性大小η和地表温度变率г具有很好的相关性,相关系数达到0.566以上,证明了新建立指标的合理性.下垫面不均匀性大小η和LAS、ECS观测的感热通量差异HLAS-HECS具有很好的一致性,相关系数达到0.634.下垫面不均匀性对LAS和ECS的感热通量差异影响显著,下垫面越不均匀LAS和ECS测量的感热通量差异越大.对两主风向分别进行分析,在E-SE风向范围η和HLAS-HECS的相关系数为0.430,HLAS和HEC拟合的线性趋势系数为1.279,在SW-W风向范围η和HLAS-HECS的相关系数为0.680,HLAS和HEC拟合的线性趋势系数为1.297.下垫面不均匀性的影响程度越大,LAS和ECS观测的感热通量差异越大.

A new index for land surface inhomogeneity and its impact on sensible heat flux measured by Large Aperture Scintillometer(LAS) over eastern Gansu of Loess Plateau

There are few quantitative researches focused on the influence of inhomogeneous land surface condition on sensible heat fluxes measured by Large Aperture Scintillometer(LAS) and Eddy Covariance System(ECS) at present. In this paper, based on the observed land surface process data in two prevailing wind directions(E-SE and SW-W) at Qingyang site in the Loess Plateau during June and July 2012, firstly, a quantitative index representing the degree of land surface inhomogeneity was established, and then an analysis was made of the relationship between surface inhomogeneity and surface temperature variability and its influence on the difference between LAS and ECS measured sensible heat fluxes. Results showed that the land surface inhomogeneity η had a good correlation with surface temperature variability г with a correlation coefficient up to 0.566, indicating that η can well represent land surface inhomogeneity. η also had a good consistency with the difference between LAS and ECS measured sensible heat fluxes(H_LAS-H_ECS), its correlation coefficient being up to 0.634. η significantly influenced the difference between LAS and ECS measured sensible heat fluxes. The more inhomogeneous η was, the greater H_LAS-H_ECS was. For the two prevailing wind directions, η had a correlation coefficient of 0.430 with H_LAS-H_ECS in E-SE wind direction, the fitting coefficient being 1.279; η had a correlation coefficient of 0.680 with H_LAS-H_ECS in SW-W wind direction, the fitting coefficient being 1.297. LAS and ECS measured sensible heat fluxes will have a greater difference when the influence of land surface inhomogeneity is larger.