流动沙丘涡度相关通量的坐标旋转订正与对比研究

摘要/Abstract

摘要： 复杂下垫面导致近地面大气运动具有特殊的动力学和热力学特征，进而影响物质和能量的交换过程。以科尔沁流动沙丘7月份涡度数据为例，分析由于地形引起的风速、旋转角度β的变化，采用二次旋转法（DR）和平面拟合法（PF）对水热通量、数据质量对比分析，结果表明：（1）地形平缓区（180°~330°）垂直风速>0，β在1.677 3°左右；地形陡峭区（330°~180°）垂直风速<0，β在-1.648 6°左右。（2）DR法和PF法对潜热通量影响很大，分别增加17%和减小15%，DR法订正前后水热通量相关性均高于PF法。（3）DR法和PF法订正后的数据分别有89.6%和89.3%通过湍流发展的充分性检验；DR法订正前后摩擦风速相关性高于PF法；能量闭合率分别提高了3.47%和2.78%。（4）整个生长季中，6、8月订正后涡度数据质量有较好的提高。因此，DR法更适用于起伏较大的流动沙丘。研究结果充分考虑地形对涡度数据影响，为科尔沁沙地及具有相似地形的地区涡度数据的合理使用提供参考。

Abstract: The specific dynamics and thermodynamics characteristics of atmospheric motion near the ground are a result of the complex underlying surfacewhich affects the exchange process of matter and energy. The sandmeadow ecotone area of the Horqin sandy land is a typical region with complex terrain, and has unique eco-hydrological characteristics. At present, there are many laws to analyze flux by eddy covariance for the desert ecosystem, but the study for correction of eddy covariance flux is still very weak over the complex underlying surface in sandy land. Based on the observation data of July on mobile dune in Horqin Sandy Land, the paper firstly analyzed the changes of wind speed and the rotation angle of coordinate correction(β)which caused by terrain,then compared sensible and latent heat flux, the surface energy closure rate and data quality(the turbulence characteristics and wind friction velocity)corrected through Double rotation and Planar fit. Results show as follows:(1)In gentle topography area(200°-300°), vertical wind velocity(w)is over zero, and the average vertical wind velocity(W)is 0.163 m·s^-1; in steep topography area(330°-180°), w is less than 0, and W is -0.071 m·s^-1. (2) β corrected by Double rotation on gentle topography is around 1.677 3°;on steep topography,it is around -1.648 6° and has more concentrated dates. β corrected by Planar fit is around 0.2°.(3)Sensible heat fluxes(H)corrected by DR is in accord with measured value, while latent heat fluxes(LE)increasesby 17%. After corrected by PF, H and LE reduces by 4.5% and 15%, respectively. This indicates that both DR and PF have asignificant influence on LE. The R² of the correlation between H and corrected H, LE and corrected LE by DR are 0.988 2 and 0.870 8, respectively, which are both higher than thosecorrected by PF.(4)Analysis of data quality evaluation indexshow that there are 10.4% and 10.7% of the measure data of the turbulence characteristic beyond the scope of the theoretical value ±30%, after corrected by DR and PF. The consistency between measure data and theoretical value in steep topography area is poor. Wind friction velocity corrected by DR(R²=0.954)has higher correlation with the one before corrected(R²=0.933)than that corrected by PF(R²=0.933). The surface energy closure rate increases by 3.47% and 2.78% after corrected by DR and PF, respectively. Overall, the topography of mobile dune is quite uneven, plane fitted by planar fit cannot change with the variety of topography, therefore, for undulating mobile dunes, the performance of DR is better than PF.

Key words: mobile dune, eddy covariance, double rotation, planar fit, flux correction

中图分类号:

P931.3

王丹, 刘廷玺, 张圣微, 段利民, 马鹏飞, 陈小平. 流动沙丘涡度相关通量的坐标旋转订正与对比研究[J]. 干旱区地理, 2017, 40(5): 1038-1046.

WANG Dan, LIU Ting-xi, ZHANG Sheng-wei, DUAN Li-min, MA Peng-fei, CHEN Xiao-ping. Comparison of coordinate rotation correction methods for eddy covariance flux over mobile dune[J]. , 2017, 40(5): 1038-1046.

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