A numerical model of the sudden stratospheric warming mechanism
A numerical model of the sudden stratospheric warming mechanism
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平流层突然变暖机制的数值模型
DOI：
10.1029/jc079i033p04989
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发表时间：
1974
影响因子：
--
通讯作者：
J. Geisler
中科院分区：
文献类型：
--
作者：
J. Geisler
发展了一个简单的数值模式来研究行星波和纬向流的相互作用，这被认为是平流层突然变暖的原因。该波是由等温大气底部的启动强迫产生的，并垂直传播到初始纬向气流廓线中，该廓线随后响应于该波垂直结构的水平热通量而随时间演变。模型的主要假设是β平面几何，并忽略了波动方程中演变的纬向流的纬向依赖性。结果表明，松野数值处理中增温事件的机制包含在该模式中，而不是基于这些简化假设。对不同模式参数值的积分表明，增温的某些特征与耗散以及波浪强迫的性质、幅度和持续时间有关。然后，我们利用该模型详细地分析了强迫波和瞬变自由模的线性叠加引起的振荡位涡输送行为，并确定这是触发非线性反馈产生变暖事件的机制。这种振荡的幅度是是否发生变暖的决定性因素。另一组模型运行显示了发生变暖所需的时间与初始纬向气流剖面的相关性。这表明，当初始纬向气流构型为其中一个自由模是静止的时，波的共振强迫对于变暖的产生并不是特别有利。
A simple numerical model is developed to study the planetary wave and zonal flow interaction that is thought to be responsible for a sudden stratospheric warming. The wave is generated by switch-on forcing at the base of an isothermal atmosphere and propagates vertically into an initial zonal flow profile that subsequently evolves in time in response to vertically structured horizontal heat flux by the wave. The principal model assumptions are β plane geometry and neglect of latitudinal dependence of the evolving zonal flow in the wave equation. Results indicate that the mechanism responsible for the warming event in a numerical treatment by Matsuno that is not based on these simplifying assumptions is contained in this model. Integrations for different values of model parameters show the dependence of certain features of the warming on dissipation and on the nature, amplitude, and duration of the wave forcing. We then use the model to analyze in detail the behavior of oscillating potential vorticity transport arising from linear superposition of the forced wave and transient free modes and establish this as the mechanism that triggers the nonlinear feedback that produces the warming event. The amplitude of this oscillation is the decisive factor in whether or not a warming occurs. A further set of model runs shows the dependence of the time it takes for a warming to occur on the initial zonal flow profile. These show that resonant forcing of the wave, occurring when the initial zonal flow configuration is such that one of the free modes is stationary, is not particularly favorable for the production of a warming.