Gaoyuan qixiang (Feb 2022)
Study on the Characteristics of Atmospheric Turbulence Exchange in the Lower Reaches of the Lhasa River in the Eastern Qinghai-Xizang Plateau
Abstract
Matter and energy between the land and atmosphere are transported with turbulent movement.Eddy covariance technology is an important way to evaluate atmospheric resources.It plays an important role in turbulence characteristics and accurate flux observation research.In this study， we analyzed the characteristics and similarity of turbulence spectra under different atmosphere conditions in the growing and non-growing seasons using closed-path eddy covariance system of Caigongtang flux station for the underlying surface of the typical grassland in the lower reaches of the Lhasa River in the eastern Qinghai-Xizang Plateau from August to November， 2020.The results showed： （1） During the growing season from August to September， the average daily net ecosystem CO2 exchange （NEE） was -2.3 gC·m-2·d-1， and the average daily ET was 1.8 mm·day-1， During the non-growing season from October to November， the average daily NEE was 1.1 gC·m-2·d-1， and the average daily ET was 0.3 mm·day-1； （2） The normalized spectra of three-dimensional （u， v and w） direction of turbulent wind speed and temperature had obvious sub-regions of inertia， the slope of the spectra density curve conformed to the -2/3 law， and the normalized co-spectra of the vertical direction （w） turbulent wind speed and temperature， CO2 and H2O gas concentrations is higher than -4/3 law； （3） The daily variation of atmosphere stability during the growing and non-growing seasons was similar， mainly decreasing with the increase of momentum flux， but the normalized standard deviation （σ/u*） fitting results of wind speed in each direction were different.During the growing season， σu /u*，σv /u*，and σw /u* were 2.84， 2.73， and 1.07， respectively.During the non-growing season， the three increased to 3.23， 3.19， and 1.22， respectively.The increase in normalized standard deviation of horizontal wind speed was obvious during the non-growing season， so the parameterization scheme of the similarity law of turbulent wind speed during the growing and non-growing seasons should be considered separately.The closed-path eddy covariance system can better realize the flux observation in this study area， and this conclusion can provide the basis for the land surface parameterization scheme that considers the similarity of the turbulent wind speed during the growing and non-growing seasons， which helps to observe the atmospheric resources more accurately.
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