地形和湍流交换非均匀对边界层Ekman抽吸的影响.pdfVIP

南京大学学报(自然科学) 第43卷 第6期 Vo1．43，No．6 JOURNAL OF NANJING UNIVERSITY 2007年 l1月 NOV．，2007 (NATURAL SCIENCES) 地形和湍流交换非均匀对边界层Ekman抽吸的影响 郑启康，王 元 ，伍荣生 (南京大学大气科学系中尺度灾害性天气教育部重点实验室，南京，210093) 摘 要： 利用地转动量近似理论，讨论地形和湍流交换系数K存在水平不均匀的条件下，获得了边界 层顶Ekman抽吸的解析结果和动力特征．研究表明：在不考虑地形强迫情况下，湍流交换系数的水平变 化对Ekman抽吸有明显的影响，而且这种影响的强弱与Rossby数大小有关．而在地形与湍流交换系数 的共同作用下，地形的影响是边界层顶的垂直速度分布的主导性因素． 关键词： 地形，湍流交换系数，Ekman抽吸 中图分类号： P 404 The Effect of Inhomogeneous Terrain and Eddy Diffusivity on Ekman Pumping in the Planetary Boundary Layer Zheng Qi—Kang，Wang Yuan”，Wu Rong—Sheng (Key Laboratory of Mesoscale Severe Weather／MOE and Department of Atmospheric Sciences，Nanjing University，Nanjing，210093，China) Abstract： By using the framework of Geostrophic Momentum Approximation(GMA)，the coherent effect for both horizOntal variation of eddy diffusivity and the terrain on Ekman Pumping in the planetary boundary layer(PBL)is investigated．Under such theoretic consideration，the analytic solution of the Ekman Pumping and its dynamic characteristics has been obtained．The results showed that without the topographic effect，the sole effect of horizontal inhomogeneous eddy diffusivities play an important role to reshape the profile of Ekman Pumping as well as its vertical velocity；the strengthening and weakening of vertical velocity heavily depends on Rossby number．On the other hand，under the effect of inhomogeneous terrain，the inhomogeneous topographic effect is a dominating farce for the distribution of Ekman Pumping intensity，even the inhomogeneous eddy diffusivity is considered． Key words： terrain，eddy diffusivity，Ekman Pumping