Rayleigh Friction, Newtonian Cooling, and the Linear Response to Steady Tropical Heating*
Rayleigh Friction, Newtonian Cooling, and the Linear Response to Steady Tropical Heating*
复制标题
瑞利摩擦、牛顿冷却和稳定热带加热的线性响应*
DOI：
--
复制
发表时间：
2000
期刊：
影响因子：
--
通讯作者：
E. Sarachik
中科院分区：
文献类型：
--
作者：
Zhaohua Wu;D. Battisti;E. Sarachik
进行了一系列的研究，以检查热带大气对规定的稳定的，大规模的，升高的热源（即，持续降水的地区）。特别强调的是放在两个理想化的情况下，其中耗散是完全通过瑞利摩擦或牛顿冷却的表面风响应。从赤道β平面上的线性化方程出发，理论论证表明这两种模型的解存在质的差异。一个干的光谱原始方程模式的大气，并确认从分析研究中得到的结果。数值模拟和理论分析的结果一致表明，瑞利摩擦和牛顿冷却在热带大气中起着完全不同的作用。牛顿冷却使垂直方向的大气运动均匀化，在热源底部以下发现强烈的垂直均匀风。当瑞利摩擦占主导地位时，由热源驱动的环流被限制在热源所在的层中。它还表明，一个强大的Hadley环流与合理的强瑞利摩擦，但不是单独与牛顿冷却。最后，数值解的情况下，牛顿冷却均匀作用在垂直和瑞利摩擦包括在低层大气中粗略地模仿在边界层中的动量耗散。简单边界层的引入大大减少了在牛顿冷却单独情况下支持的表面循环。这些结果表明，如果热源位于边界层顶部以上，则不太可能由升高的热源驱动显著的表面环流。
A series of studies are performed to examine the response of the tropical atmosphere to a prescribed steady, large-scale, elevated heat source (i.e., a region of persistent precipitation). Special emphasis is placed on the surface wind response in two idealized cases in which dissipation is achieved exclusively by Rayleigh friction or by Newtonian cooling. Starting from the linearized equations on an equatorial beta plane, theoretical arguments are presented that suggest there are qualitative differences in the solutions of these two models. A dry spectral primitive equation model of the atmosphere is employed and confirms the results obtained from the analytical studies. The results from both the analytical study and the numerical simulations are consistent in showing that Rayleigh friction and Newtonian cooling play totally different roles in the tropical atmosphere. Newtonian cooling homogenizes the atmospheric motion in the vertical direction, and a strong, vertically uniform wind is found below the base of the heat source. When Rayleigh friction dominates, the circulation driven by the heat source is confined to the layer where the heat source is located. It is also shown that a strong Hadley circulation is associated with reasonable strong Rayleigh friction, but not with Newtonian cooling alone. Finally, the numerical solution is found for the case where Newtonian cooling acts uniformly in the vertical and Rayleigh friction is included in the lower atmosphere to mimic crudely the dissipation of momentum in the boundary layer. The introduction of the simple boundary layer dramatically reduces the surface circulation that was supported in the Newtonian cooling alone case. Together these results suggest a significant surface circulation is unlikely to be driven by an elevated heat source if it resides above the top of the boundary layer.