黑河下游绿洲近地层湍流输送特征研究

分析2003年9月5-27日在黑河下游额济纳绿洲取得的近地面层湍流观测资料,讨论无量纲湍流方差与稳定度参数Z/L的关系.无量纲风速分量σu/u*、σv/u*和σw/u*在不稳定层结与稳定度Z/L满足1/3次方时,符合Monin-Obkuhov相似理论.在近中性时,σu/u*、σw/u*值比平坦下垫面的略小些,σv/u*值比平坦下垫面的略大.无量纲温度脉动方差和湿度脉动方差在对流状态下与Z/L满足-1/3次方,在稳定和不稳定层结下,随|Z/L|减小而增大.地面热量以感热输送为主,感热通量峰值约为250 W/m2,潜热通量的峰值为170 W/m2;夜间潜热通量较小,感热通量则出现负值.动量通量日间平均在0.2-0.3 N/m2,峰值为0.31 N/m2.黑河下游绿洲柽柳林动力学粗糙度比HEIFE戈壁及其他绿洲下垫面的大,中性时z0m=0.47551 m.中性状态下动量整体输送系数CD=22.2×10-3,不稳定层结时平均值CD=10.3×10-3,稳定层结时平均值CD=7.2 × 10-3.热量整体输送系数CH,中性状态下CH=3.2 × 10-3,不稳定层结时平均值为CH=3.3×10-3,稳定层结时平均值为CH=2.7×10-3.

A study on turbulent characteristics of the surface layer in Ejina oasis of the lower reach of Heihe

The turbulent data observed in the Tamarisk scrub over Ejina oasis in the lower reaches of Heihe River from September 5 to 27, 2003 are used to investigate the relation between dimensionless turbulent speed variances and stability parameter Z/L. The results show that under the unstable stratified condition the stability parameter (Z/L) dependence of , , and can be fit to a power law with a power law index of 1/3, in accordance with the Monin-Obkuhov similarity theory. Under the near neutral condition, , / are slightly smaller/larger than their counterparts over the flat underlying surface. Under the convective condition, the stability parameter (Z/L) dependence of variances of dimensionless temperature and specific humidity fluctuations can be fitted to a power law with an index of -1/3, and under both the stable and unstable stratification the variance increases with the reduction of | Z/ L|. The sensible heat flux dominates the surface heat fluxes, with a peak value of about 250 W.m-2 for sensible heat and 170 W.m-2 for latent heat; and in night-time the latent heat flux is smaller, the sensible heat flux becomes negative. In day-time, the momentum flux ranges from 0.2 to 0.3 N.m-2 with a peak value of 0.31 N.m-2. The aerodynamic roughness length in the Ejina Tamarisk scrub is larger than those over the Gobi and other oasis underlying surfaces in the HEIFE, with =0.47551m under the neutral stratification. The bulk momentum transfer coefficient under the neutral, unstable, and stable stratification are 22.2×10-3, 10.3×10-3, and 7.2×10-3 and the corresponding values of the bulk heat transfer coefficient are 3.2×10-3, 3.3×10 -3,and 2.7×10 -3, respectively.