那曲高寒草地上四种地表通量计算方法的对比

Comparison of Four Methods for Calculating Surface Fluxeson Alpine Grassland at Naqu

利用中国科学院那曲高寒气候环境观测研究站2013年9月至2014年8月自动气象站(AWS)和涡动相关系统(EC)的观测资料,基于空气动力学法、地表能量平衡组合法、总体输送法以及涡动相关法,计算了高寒草地下垫面的湍流通量,并对不同方法计算结果间的一致性和差异性进行了分析。结果表明,不同方法计算的湍流通量特征具有明显的差异。地表能量平衡组合法满足能量平衡关系,但在早晨和傍晚层结转换期间,计算的湍流通量出现异常不稳定值;空气动力学法计算的湍流通量在整个观测期与涡动相关法计算的湍流通量相关性最高,但在大气稳定度参数接近0,计算结果不稳定;总体输送法计算的通量数据在地气温差为负值时发散明显,但该方法原理简单,适合在只有常规观测项目的业务气象站或在气象观测项目不全的野外台站使用。空气动力学法和地表能量平衡组合法与涡动相关法的湍流通量的平均偏差相对较小,而总体输送法平均偏差相对较大。研究方法和结果除了为这些方法的使用提供参考外,也为建立长时间通量序列提供了一个较为合理的依据,有助于深入了解高原地气相互作用。

The near-surface layer gradients observed data of wind speed, temperature and specific humidity com- bined with the radiative and soil heat fluxes have been widely applied in estimating the surface-air turbulent ex- change over decades. However, different methods may produce significant differences and errors in their results. In this paper, the observational data of automatic weather station （AWS） and eddy correlation system （EC） from Naqu Station of Plateau Climate and Environment in the Norther Tibetan Plateau from September 2013 to August 2014 were used to calculate turbulent fluxes by the eddy covariance, the aerodynamic method, the combi- nation methodand the mass transfer method and analysis the consistency and difference among the calculated re- sults. The results show that the characteristics of turbulent fluxes calculated by different methods have obvious differences. The combination method satisfies the energy balance relationship. However, the turbulent fluxes ap- pear to be abnormally unstable during the morning and evening. The turbulent fluxes calculated by the aerody- namic method have the highest correlation with the turbulent fluxes calculated by the eddy correlation method. But when the atmospheric stability parameter is close to zero, the calculation result is unstable. When the difference between the surface temperature and the air temperature is less than zero, the flux data calculated by the mass transfer method show obvious divergence. But this method is simple in principle and suitable for field sta- tions which have few observation instruments and incomplete meteorological observation stations. The mean devi- ation of the turbulent flux calculated by the aerodynamic method and the combination method is smaller, while the average deviation of the turbulent flux calculated by the mass transfer method is larger. The results of this study provide reference for the use of these methods. Besides, the results of this study provide a reasonable basis for the establishment of long time flux series. Finally this study will help us to understand the interaction between the surface and the atmosphere.