Gravity-wave dynamics of the hierarchical structure of Super cloud clusters.
Gravity-wave dynamics of the hierarchical structure of Super cloud clusters.
复制标题
超级云团层次结构的重力波动力学。
DOI：
10.2151/jmsj1965.78.4_301
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发表时间：
2000
影响因子：
3.1
通讯作者：
Y. Hayashi
中科院分区：
文献类型：
--
作者：
A. Numaguti;Y. Hayashi
利用一个简单的二维云高湿过程模式，成功地模拟了东移热带超级云团（SCC）和嵌入西移准周期云团（QPCC）的层次结构。模型结果清楚地显示了云活动的生命周期。云区开始为低层的浅云，发展为深对流，成为头重脚轻的云，并衰减。引力波包被激发的增长和衰减的这个云和传播的东西。向西传播的重力波与云活动耦合，形成向西移动的QPCC。另一方面，向东传播的波并不立即与深对流活动相耦合。深对流云只有在对流层中低层充分增湿冷却后才发展。新的对流云团准周期性地出现在东部，导致QPCC的包层东移，形成一个东移的SCC。这表明，由加热的增长和衰减与头重脚轻的垂直廓线的两个垂直模式的重力波的激发是必要的这种层次结构。特别是浅层重力波单元引起的净向上位移对新QPCC的产生有重要作用。虽然在没有东西不对称的外部来源的非旋转大气中，向东移动的SCC和向西移动的SCC都是可能的，但是在存在一些外部不对称性的情况下，例如β效应、平均纬向风切变或由于WISHE（wind-induced surface heat exchange）效应引起的潜热通量的不对称性，可以选择向东移动的SCC。
The hierarchical structures of eastward-moving tropical super cloud clusters (SCC) and embedded westward-moving quasi-periodic cloud clusters (QPCC) are successfully simulated by a simple longitude-height two-dimensional model with simple moist processes. The model results clearly show a life cycle of cloud activity. The cloud area starts as a low-level shallow cloud, develops into deep convection, becomes a top-heavy cloud, and decays. Gravity-wave packets are excited by the growth and decay of this cloud and propagate both eastward and westward. The westward-propagating gravity waves are coupled with cloud activity and form westward-moving QPCC. On the other hand, the eastward propagating waves are not immediately coupled with deep convective activity. A deep convective cloud develops only after the low and middle troposphere is sufficiently moistened and cooled. The quasi-periodic emergence of the new convective cloud to the east results in the eastward movement of the envelope of QPCC, forming an eastward-moving SCC. It is suggested that the excitation of gravity waves of two vertical modes by grow and decay of the heating with top-heavy vertical profile is essential to this hierarchical structure. Especially, the net upward parcel displacement due to the shallow gravity-wave cell have a important role in the generation of new QPCC. Although both eastward-moving SCC and westward-moving SCC are possible in a non-rotating atmosphere with no external origins of east-west asymmetry, eastward-moving SCC can be selected under existence of some external asymmetry, such as the beta effect, mean zonal wind shear, or asymmetry of latent heat flux due to WISHE (wind-induced surface heat exchange) effect.