夏季青藏高原低涡的切向流场及波动特征分析

从大气动力学原理出发,将高原低涡视为受热源强迫的边界层内涡旋,建立了柱坐标下满足梯度风平衡的低涡控制方程组,分析高原低涡切向流场的基本特征.在此基础上,通过求解线性化涡旋模式,得出高原低涡中各类波动的频散关系及其特征,同时定性讨论了热力作用对混合波动的影响以及混合波动与高原低涡流场特征的联系.使用中尺度数值模式WRF分...

Characteristics of the tangential flow field of the Tibetan Plateau vortices and associated waves

From the dynamic principle, the Tibetan Plateau vortices were assumed as the vortices in the boundary layer forced by diabatic heating and friction. In order to analyze the basic characteristics of tangential flow field of the vortices, the control equations for the vortices were then established in the column coordinate with the balance of gradient wind assumed. Based on this, the type of mixed waves and their dispersion characteristics were deduced by solving the linear model. In addition, the impact of diabatic heating on the mixed waves and the connection of mixed waves with the characteristics of flow field of the vortices were qualitatively discussed. Two Numerical simulations were also done by the WRF which was developed by the NCEP/NCAR. Among them one is an idealized large eddy simulation whose aim was to validate the tangential flow field deduced from the control equations. The other is the simulation of a Tibetan Plateau vortex on August 14, 2006 using the WRF with triple nested domains employed. The high resolution model output data were than analyzed. The results show that the tangential flow field of the Tibetan Plateau vortices is cyclonic convergence below the critical height and the intensity weakened with height, while there are anti cyclonic divergence flows above the critical height and the intensity increased with height. When the heating field is in the form of center heating, the cyclonic tangential flows increased with time below the critical height and the anti cyclonic tangential flow increased with time above the critical height; the intensity of the tangential flow field is increased below the critical height when there are cyclonic flows in the boundary layer, and the intensity of tangential flow field is decreased below the critical height when there are anti cyclonic flows in the boundary layer. The Tibetan Plateau vortices may contain the mixed Inertial Gravity Vortex Rossby waves and changes in the heating with radial and its radial gradient variation will have great impact on the mixed waves.