中文摘要：

利用科尔沁半干旱风沙草原区涡度相关观测数据,计算并分析了不同大气稳定度条件下湍流的功率谱和协谱。结果表明：经向风速与纬向风速的功率谱在大气不稳定层结、近中性层结、稳定层结条件下谱形均相似,并遵循-2/3定律;近中性层结条件下垂直风速的功率谱没有惯性子区,此时仪器对脉动信号的捕捉不够完全,稳定层结条件下垂直风速功率谱表明观测层产生了泄流和平流;CO2和H2O浓度的功率谱分析表明,红外气体分析仪对高频信号的响应能力能够满足实际观测的需要,其功率谱的谱峰随大气稳定度的增强而向高频转移;垂直风速与3种标量的协谱谱形相似,不同大气稳定度下协谱惯性子区长度随大气稳定度的增强而变短,且均符合-4/3定律,说明三维超声风速仪与红外气体分析仪的空间间隔不会对通量观测结果造成显著影响。

英文摘要：

By using eddy covariance method,this paper dealt with the power spectra and cospectra of turbulence under three atmospheric stability regimes,i.e.,unstable,near neutral,and stable,in Horqin semi-arid sandy grassland.The power spectra of longitudinal and lateral velocities under the three atmospheric stability regimes were similar,and in accordance with the-2/3 law.The power spectra of vertical wind speed had no inertial sub-ranges under near neutral atmospheric stratification,which indicated that the three-dimensional sonic anemomcter didn＇t totally capture the signal.Under the stable atmospheric condition,there were horizontal turbulence motions and molecular diffusions.Moreover,the power spectra of both CO 2 and H 2O illustrated that the open-path eddy covariance system could satisfy the estimation of turbulence fluxes over canopy,and the peaks of the power spectra were shifted to the high frequency end.The cospectra of vertical wind speed with three scalars were similar,with the inertial sub-ranges of cospectra becoming shorter from unstable to stable atmospheric conditions and conforming to the-4/3 law,which illustrated that the spatial separation of instruments didn＇t affect the observed fluxes.