On the Maintenance of the Trade Winds
On the Maintenance of the Trade Winds
复制标题
关于信风的维护
DOI：
10.1111/j.2153-3490.1956.tb01231.x
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发表时间：
1956
期刊：
影响因子：
2
通讯作者：
J. Malkus
中科院分区：
文献类型：
--
作者：
J. Malkus
研究了下游贸易流的大尺度特征与小尺度对流运动的影响之间的关系。小规模过程通过非绝热加热和剪切应力的产生对整体循环施加限制。这些约束可以根据描述太平洋贸易北部部分的平均流量的理论模型来表述，该模型先前已进行过一些详细的观测研究。在具有非绝热加热的简化无摩擦模型中，流动在质量上表现出许多重要的特征，例如沉降、下游加速、增加的垂直风切变和压降。然而，只有在引入摩擦应力时，运动场和压力场才与观察到的加热在数值上相关。人们发现，无需采用直接测量即可描述较低行业中的摩擦应力分布，从而为模型提供后续的独立检查。本文的最后部分考虑了运动场、加热场和应力场之间可能的准稳态重排，这可能被视为系统关于其平均条件的缓慢波动的步骤。这样做是为了询问这些属性中任何一个属性的变化是否会导致其他属性的重新调整，从而恢复均值或加速偏离均值。尽管这种分析因缺乏有关加热和应力分布之间相互作用的知识而受到阻碍，但一项样本计算表明，加热的减少可以缓解沉降，因此有望恢复对流，从而恢复加热。由此可见，低层交易中小规模运动与大规模运动之间存在稳定耦合，这可能对维持流动的高度稳定性发挥作用。如果这个模型可以接受，那么风稳定性在对流层上方迅速消失的事实就得到澄清。 DOI：10.1111/j.2153-3490.1956.tb01231.x
A relation between the large-scale features of the lower trade stream and the effects of small-scale convective motions is investigated. The small-scale processes impose constraints upon the over-all circulation through non-adiabatic heating and the production of shearing stresses. These constraints may be formulated in terms of a theoretical model describing the mean flow in a section along the northern portion of the Pacific trade, which has previously been studied observationally in some detail. In a simplified frictionless model with non-adiabatic heating the flow exhibits qualitatively many of the important features of the trades, such as subsidence, and a downstream acceleration, increased vertical wind shear, and pressure drop. The motion and pressure fields become numerically related to the heating as observed, however, only upon the introduction of frictional stresses. It is found possible to describe the frictional stress distribution in the lower trades without resorting to direct measurements, which thus provide a later independent check of the model. The last sections of the paper consider possible quasi-steady rearrangements between the fields of motion, heating, and stress which might be regarded as steps in the slow fluctuations of the system about its average condition. This is done to inquire whether changes in any one of these properties will produce readjustments in the others acting to restore the mean or to accelerate the departure from it. Although such an analysis is handicapped by lack of knowledge concerning the interaction between the heating and stress distributions, one sample calculation suggests that a reduction of heating acts to relieve the subsidence and might thus be expected to restore the convection and thereby the heating. A stable coupling between small- and large-scale motions in the low-level trades is thus indicated, which may play a role in maintaining the high steadiness of the flow. The fact that the wind steadiness vanishes rapidly above the convective layer is clarified if this model is acceptable. DOI: 10.1111/j.2153-3490.1956.tb01231.x