大口径闪烁仪和涡动相关仪测量大气折射率结构常数的比较

Comparison of Large Aperture Scintillometer and Eddy-Covariance System Measurements with Structure Parameter of Refractive Index of Air

利用大理国家气候观象台大口径闪烁仪(Large Aperture Scintillometer,LAS)和涡动相关系统(Eddy-covariance System,EC)在洱海湖滨农田下垫面的同步观测资料,初步分析了两种仪器测量大气折射率结构常数C2n的异同特征。结果表明,两种仪器测量的C2n具有较好的相关性,相关系数达0.73。LAS测量的C2n数量级为10-17~10-14m-2/3,EC测量的数量级为10-16~10-13m-2/3。在典型晴天、多云和阴天条件下,两种仪器测量的有植被水田和无植被旱地的C2n均表现出明显的日变化特征,日出后1 h和日落前1 h左右出现最小值,中午前后达到最大值,而且这种日变化趋势基本一致。测量结果在数量级上的差异是由测量高度、测量方法、仪器噪声、天气状况、风速风向、净辐射通量和大气稳定状态等因素造成的。

Based on the observational data of Large Aperture Scintillometer(LAS) and Eddy- covariance System(EC) from Dali National Climate Observatory,the structure parameter of the refractive index of air( C2n)between LAS and EC measurement was analyzed.The results showthat there was a very good correlation between log C2 nvalues measured by two kinds of instruments with the correlation coefficient up to 0.73.The values of C2 nmeasured by LAS lay between 10-17 and 10-14m-2/3,and measured by EC lay between 10-16 and 10-13m-2/3.The diurnal variations of C2 nwere evident and the values of C2 nreached the maximum in the afternoon and the minimum in the sunrise and sunset for a clear,cloudy and overcast day in paddy field covered with vegetation and dry land covered with no vegetation.The diurnal variation tendency of C2 nmeasured by EC and LAS were consistent.However,the most values of C2 nmeasured by EC were 1 hour order bigger in magnitude than measured by LAS due to the effects of installation height, measurement method, noise level of electronics,sky condition,wind speed and direction,net radiation fluxes,atmospheric stability and so on,wherein the installation height was the major factor.