Noninstantaneous Wave-CISK for the Interaction between Convective Heating and Low-Level Moisture Convergence in the Tropics
Noninstantaneous Wave-CISK for the Interaction between Convective Heating and Low-Level Moisture Convergence in the Tropics
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DOI：
10.1175/jas-d-19-0003.1
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发表时间：
2019-06
影响因子：
3.1
通讯作者：
Yan Liu;Z. Tan;Zhaohua Wu
中科院分区：
文献类型：
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作者：
Yan Liu;Z. Tan;Zhaohua Wu
使用具有第二类波浪条件不稳定性 (CISK) 参数化的全局干燥原始方程模型研究热带对流加热和热力强迫环流之间的相互作用。结果表明，无论收敛水分的直接消耗比例如何，深层对流加热都很难通过低水平的水分收敛来维持自身。相反，当分数较大时，浅对流加热及其强制循环表现出小尺度的优先生长。由于“CISK灾难”主要来自于常规波-CISK中水分-对流反馈的瞬时特征，因此提出了非瞬时波-CISK，它突出了对流加热积累和/或收敛水分消耗的积累-消耗（AC）时间尺度。在新浪潮CISK中，一旦水分汇聚，潜热就会在AC时间尺度内逐渐释放。从这个意义上说，对流加热不仅与当前时间的瞬时水汽辐合有关，而且还与AC时间尺度过去一段时间内发生的水汽辐合有关。非瞬时波-CISK可以保证更大尺度上对流加热和/或水汽辐合的发生，进而有利于长波的生长，从而解决CISK灾难问题。在新波CISK和2天AC时间尺度下，模拟的对流加热驱动系统与观测到的对流耦合开尔文波具有很大的相似性。
The interaction between tropical convective heating and thermally forced circulation is investigated using a global dry primitive-equation model with the parameterization of wave-conditional instability of the second kind (CISK). It is demonstrated that deep convective heating can hardly sustain itself through the moisture convergence at low levels regardless of the fraction of immediate consumption of converged moisture. In contrast, when the fraction is large, shallow convective heating and its forced circulation exhibit preferred growth of small scales. As the “CISK catastrophe” mainly comes from the instantaneous characters of moisture–convection feedback in the conventional wave-CISK, a noninstantaneous wave-CISK is proposed, which highlights the accumulation–consumption (AC) time scale for the convective heating accumulation and/or the converged moisture consumption. In the new wave-CISK, once moisture is converged, the release of latent heat takes place gradually within an AC time scale. In this sense, convective heating is not only related to the instantaneous moisture convergence at the current time, but also to that which occurred in the past period of the AC time scale. The noninstantaneous wave-CISK could guarantee the occurrence of convective heating and/or moisture convergence at larger scales, and then favor the growth of long waves, and thus solve the problem of CISK catastrophe. With the new wave-CISK and AC time scale of 2 days, the simulated convective heating-driven system bears a large similarity to that of the observed convectively coupled Kelvin wave.