The Physical Mechanism of CISK and the Free-Ride Balance
The Physical Mechanism of CISK and the Free-Ride Balance
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CISK 的物理机制与搭便车平衡
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
J. McBride
中科院分区：
文献类型：
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作者：
K. Fraedrich;J. McBride
摘要将非绝热加热和绝热冷却平衡的“搭便车”假设引入到Charney和Eliassen经典的两能级条件不稳定性模型中，研究了它的性质。当加热幅度超过修正的静态稳定性(S−aξ)时，搭便车模型被发现给出了Cask型不稳定性。搭便车解决方案在结构上与CISK解决方案非常相似，不同的是搭便车增长率与规模无关。对经典CISK模型的考察表明，在不稳定有效的尺度范围内，它的增长率也与尺度无关，并且在这个尺度范围内，搭便车和经典模型本质上是相同的。这导致了对CISK的新的物理解释。考虑到积雨云的加热率与低层涡度成正比(通过Ekman抽运效应)，从平衡和低空涡度的角度解释了CISK机制。
Abstract The properties of the “free-ride” assumption of balance between diabatic heating and adiabatic cooling are investigated by incorporating it into the classical two-level CISK (Conditional Instability of the Second Kind) model of Charney and Eliassen. The free-ride model is found to give a CISK-type instability when the heating amplitude exceeds the modified static stability (s−aξ). The free-ride solution is very similar in structure to the CISK solution, except that the free-ride growth rate is independent of scale. Inspection of the classical CISK model reveals that its growth rate is also independent of scale over the range of scales for which the instability is efficient, and over this range of scales the free-ride and the classical models are essentially identical. This leads to a new physical interpretation of CISK. Given that the cumulonimbus heating rate is proportional (through the Ekman pumping effect) to the low-level vorticity, the CISK mechanism is interpreted in terms of a balance and...