Equilibration of a Baroclinic Planetary Atmosphere toward the Limit of Vanishing Bottom Friction
Equilibration of a Baroclinic Planetary Atmosphere toward the Limit of Vanishing Bottom Friction
复制标题
斜压行星大气向底部摩擦消失极限的平衡
DOI：
10.1175/jas-d-15-0329.1
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发表时间：
2016
影响因子：
3.1
通讯作者：
G. Vallis
中科院分区：
文献类型：
--
作者：
Junyi Chai;M. Jansen;G. Vallis
摘要本文讨论了在干燥原始方程环流模式中斜压大气能否在极小的底摩擦下达到平衡，以及如何达到平衡。该模型受牛顿温度弛豫作用于规定的温度分布，并受靠近下边界的线性摩擦的阻尼。当摩擦减小4个数量级时，摩擦的动能耗散逐渐变得可以忽略不计，而“能量回收”成为主导。在这个极限下，动能在最大尺度上被转换回势能，从而在没有明显摩擦耗散的情况下关闭了能量循环。在高层和低层大气中动量通量的符号相反：在高层大气中，涡旋将动量汇聚成西风急流；然而，在低层大气中，涡旋从西风急流中分离出动量。由经向涡旋动量通量驱动的二次环流增加了斜压性。
AbstractThis paper discusses whether and how a baroclinic atmosphere can equilibrate with very small bottom friction in a dry primitive equation general circulation model. The model is forced by a Newtonian relaxation of temperature to a prescribed temperature profile, and it is damped by a linear friction near the lower boundary. When friction is decreased by four orders of magnitude, kinetic energy dissipation by friction gradually becomes negligible, while “energy recycling” becomes dominant. In this limit kinetic energy is converted back into potential energy at the largest scales, thus closing the energy cycle without significant frictional dissipation. The momentum fluxes are of opposite sign in the upper and lower atmosphere: in the upper atmosphere, eddies converge momentum into the westerly jets; however, in the lower atmosphere, the eddies diverge momentum out of the westerly jets. The secondary circulation driven by the meridional eddy momentum fluxes thus acts to increase the baroclinicity of ...