北京蟒山森林区稀疏短草地表湍流通量观测与计算比较

Measurements and Estimation of Turbulent Fluxes over a Sparse-short Grassland in Mangshan Forest Area in Beijing

利用2007年9月20日-12月8日北京蟒山森林区稀疏短草下垫面近地层湍流和辐射资料， 首先分析了动量、 感热、 潜热通量和辐射各分量的日变化特征； 然后采用Businger71方案、 Launiainen95方案和Gao方案对动量通量、 感热通量和潜热通量进行了计算， 进一步将计算结果与涡度相关系统测量值进行对比。结果表明： （1） 对于蟒山森林区稀疏短草地表而言， 感热通量约为潜热通量的2倍， 说明感热是地表可用能量的主要消耗部分； （2） 森林区稀疏短草地表反射率在0.1~0.25之间变化， 由秋季到冬季反射率略有升高； （3） 三种方案对动量通量的计算值与测量值最为接近， 相关性最高（其中， Gao方案对动量通量的计算值与测量值的相关系数达0.80）， 其次为感热通量, 潜热通量的计算结果偏差最大， 相关性最低。

A field campaign was carried out from September 20 to December 8, 2007 over a sparse-short grass in Mangshan forest area which locates in north suburb of Beijing. Radiation flux and turbulent fluxes in the near surface layer were measured at the height of 2.5 m above ground. Momentum flux, sensible flux and latent flux estimated by Businger71 scheme, Launiainen95 scheme and Gao scheme were compared with direct measurements. The results show that： （1） The sensible heat and latent heat fluxes approached the maximum values when net radiation reached its peak value around noon, and sensible heat flux were twice of the latent heat flux. This demonstrated that sensible heat is the main consumer of surface available energy for this grassland site; （2） The measurements of albedo gradually increased through this period from 0.1 to 0.25; （3） The estimate of turbulent fluxes by Gao scheme is the best, and overall, these methods generate good estimation of momentum fluxes and the worst estimation of latent heat fluxes.