Convectively Generated Gravity Waves During Solstice and Equinox Conditions
Convectively Generated Gravity Waves During Solstice and Equinox Conditions
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DOI：
10.1029/2019jd031582
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
C. Heale;T. Lund;D. Fritts
中科院分区：
文献类型：
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作者：
C. Heale;T. Lund;D. Fritts
先前的研究表明，尽管同心波和半同心波在夏季的同心波很容易在平流层中观察到，但在春分月比冬至月更容易观察到中间层同心波模式。本文采用三维非线性模型模拟了平均春分和夏至条件下对流重力波的传播和耗散，探讨了波浪破碎对这些同心模式的影响。研究发现，在春分月份，相对较弱的大气风和切变意味着波浪在破裂之前可以向上传播到较低的热层。相反，在夏至的几个月里，强烈的纬向风和切变会导致中间层的原位断裂，从而导致同心模式的破坏。当同心圆模式的西部传播部分被平流层风过滤时，东部传播部分迅速转变为中间层的湍流，使其在冬至月份不太可能观察到同心圆模式。同心模式在春分月份更为完整，因为波浪只被风过滤得很弱，在中间层发生的原位破裂相对较少。然而，原位断裂并不影响平流层的模式，平流层的形态主要由风过滤决定。这也有助于解释为什么同心和半同心模式在夏季平流层中观察到，而在中间层中却不经常观察到。
Previous studies suggest that mesospheric concentric wave patterns are more observable in the equinox months than solstice months, despite concentric and semiconcentric waves being readily observed in summer months in the stratosphere. This study uses a 3‐D nonlinear model to simulate the propagation and dissipation of convectively generated gravity waves under averaged equinox and solstice conditions to investigate the influences of wave breaking upon these concentric patterns. It is found that the relatively weak atmospheric winds and shears during the equinox months means that waves can propagate up to the lower thermosphere before breaking. In contrast, strong zonal winds and shears in the summer solstice months lead to in situ breaking in the mesosphere, which causes disruption to the concentric pattern. While the western propagating portion of the concentric pattern is filtered by the stratospheric winds, the eastern propagating portion rapidly transitions to turbulence in the mesosphere making it less likely to observe concentric patterns in the solstice months. The concentric pattern is more complete in the equinox months because the waves are only weakly filtered by winds and relatively little in situ breaking occurs in the mesosphere. However, in situ breaking does not affect the pattern in the stratosphere, where the morphology is primarily dictated by wind filtering. This also helps explain why concentric and semiconcentric patterns are observed in the summer stratosphere but not regularly in the mesosphere.