The influence of the Ekman friction on the dynamics of zonal flows (ZFs) has been studied within the framework of a quasigeostrophic model of the atmosphere with two horizontal boundaries (the underlying surface and the tropopause). It is assumed that these flows have zero potential vorticity and are caused by specified buoyancy distributions at the boundaries. It is shown that, in the case of periodic distributions, the oppositely directed vertical velocity profile of ZFs transforms into a unidirectional profile with a maximum velocity at the upper boundary and zero velocity at the lower boundary. During this transformation, the velocity at the upper boundary increases; i.e., the upper tropospheric ZFs intensify due to the Ekman friction. A similar intensification occurs also in the case of initial distributions of buoyancy of the frontal type, which induce a system of two oppositely directed jet flows located in the upper and lower halves of the atmospheric layer. Due to the Ekman friction, the axial velocity of the lower flow drops to zero and the velocity of the upper flow, gradually covering the entire troposphere, doubles. The resulting flow is a jet pressed against the upper boundary, which may be considered a prototype of a western upper tropospheric jet flow. The important structural features of such a jet, which are established within the framework of a complete nongeostrophic model, are associated with horizontal jet asymmetry and the formation of fronts (discontinuity surfaces) adjacent to the upper boundary.

中文翻译：

---

埃克曼摩擦和对流层上部纬向流的形成

已经在具有两个水平边界（下垫面和对流层顶）的大气准地转模型框架内研究了埃克曼摩擦对纬向流 (ZF) 动力学的影响。假设这些流动的潜在涡度为零，并且是由边界处指定的浮力分布引起的。结果表明，在周期性分布的情况下，ZFs 的反向垂直速度剖面转变为单向剖面，其上边界处速度最大，下边界处速度为零。在这个变换过程中，上边界处的速度增加；即，由于埃克曼摩擦，对流层上部 ZF 增强。在正面型浮力的初始分布的情况下也会发生类似的强化，这引起了位于大气层上半部和下半部的两个方向相反的射流系统。由于埃克曼摩擦，下部气流的轴向速度降至零，而逐渐覆盖整个对流层的上部气流的速度加倍。由此产生的气流是一股压在上边界上的射流，这可以被认为是西部对流层上部射流的原型。这种射流的重要结构特征是在完整的非地转模型框架内建立的，与水平射流的不对称性和与上边界相邻的锋面（不连续面）的形成有关。下部气流的轴向速度降至零，而逐渐覆盖整个对流层的上部气流的速度加倍。由此产生的气流是一股压在上边界上的射流，这可以被认为是西部对流层上部射流的原型。这种射流的重要结构特征是在完整的非地转模型框架内建立的，与水平射流的不对称性和与上边界相邻的锋面（不连续面）的形成有关。下部气流的轴向速度降至零，而逐渐覆盖整个对流层的上部气流的速度加倍。由此产生的气流是一股压在上边界上的射流，这可以被认为是西部对流层上部射流的原型。这种射流的重要结构特征是在完整的非地转模型框架内建立的，与水平射流的不对称性和与上边界相邻的锋面（不连续面）的形成有关。