Isolating the Effects of Moisture Entrainment on Convectively Coupled Equatorial Waves in an Aquaplanet GCM
Isolating the Effects of Moisture Entrainment on Convectively Coupled Equatorial Waves in an Aquaplanet GCM
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DOI：
10.1175/jas-d-18-0098.1
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发表时间：
2018-08
影响因子：
3.1
通讯作者：
Simon C. Peatman;J. Methven;S. Woolnough
中科院分区：
文献类型：
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作者：
Simon C. Peatman;J. Methven;S. Woolnough
大气环流模式中对流参数化方案的湿度卷吸率影响对流耦合波的模拟。然而，目前还不清楚这是由卷吸对波浪的影响直接引起的，还是通过相关的影响（如对基本状态的影响）间接引起的。因此，使用水行星模型，我们采用了一种新的框架，其中我们夹带的加权平均的解决湿度场和规定的纬向对称场，与权重控制的解耦参数。因此，我们可以改变夹带率的基本状态湿度独立夹带的湿度扰动，同时最大限度地减少变化的基本状态。因此，我们隔离的水分卷吸波的影响。提高夹带率增加了所有纬向波数和频率的光谱功率，增加了向东向西的功率比。开尔文波的速度随着夹带的增加而减小，这可以部分地由基本状态湿度的相关变化来解释。增加去耦参数降低了开尔文波相对于背景的光谱功率，只有长波仍然突出时，夹带几乎完全解耦的解决水分场，这表明在湿度波结构所需的对流组织成短波结构。对于长波，东向西功率比的增加，夹带率的增加不能解释的变化与波结构的耦合在湿度，但与基本状态的变化是一致的。
The rate of humidity entrainment in the convective parameterization scheme in a general circulation model affects the simulation of convectively coupled waves. However, it is unclear whether this is caused directly by the effects of entrainment on waves or indirectly through associated impacts such as on the basic state. Therefore, using an aquaplanet model, we employ a novel framework in which we entrain a weighted average of the resolved humidity field and a prescribed zonally symmetric field, with the weighting controlled by a decoupling parameter. Hence, we can vary the entrainment rate of basic-state humidity independently of the entrainment of humidity perturbations, simultaneously minimizing changes in the basic state. Thus, we isolate the effect of moisture entrainment on the waves. Enhancing the entrainment rate increases spectral power over all zonal wavenumbers and frequencies, with an increase in the ratio of eastward-to-westward power. The Kelvin wave speed decreases as entrainment increases, which can be partially accounted for by an associated change in basic-state humidity. Increasing the decoupling parameter reduces spectral power in Kelvin waves relative to the background, with only long waves still prominent when entrainment is almost fully decoupled from the resolved moisture field, suggesting the wave structure in humidity is required for convection to organize into short-wave structures. For long waves, the increase in the ratio of eastward-to-westward power as entrainment rate increases cannot be explained by the changes in the coupling with the wave structure in humidity but is consistent with the changes in the basic state.