Characterization of Moist Processes Associated With Changes in the Propagation of the MJO With Increasing CO(2).
Characterization of Moist Processes Associated With Changes in the Propagation of the MJO With Increasing CO(2).
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DOI：
10.1002/2017ms001040
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发表时间：
2017-12
影响因子：
6.8
通讯作者：
Wu J
中科院分区：
文献类型：
--
作者：
Adames ÁF;Kim D;Sobel AH;Del Genio A;Wu J
通过分析一系列NASA GISS模型模拟中MJO的湿静态能量收支，研究了导致MJO传播和维持变化的过程，作为对CO2增加的响应。它被发现在MJO传播的变化是由几个关键过程。水平水分平流，MJO传播的一个关键过程，被发现主要是由于平均水平水分梯度的增加，以提高。确定平流风异常，MJO水平尺度和干静稳定度的强度的条款，被发现表现出相反的趋势，在很大程度上抵消。此外，降低了沉淀对柱水分变化的敏感性，即，对流水分调节时间尺度的延长也会阻碍增强的传播。Adames和Kim的色散关系解释了所有这些过程，预测MJO的加速率为1.33% K−1，这与模拟中的实际相速度变化一致。对于有助于MJO维护的过程，它被发现，阻尼垂直MSE平流减少，由于垂直湿度梯度的增加。这种较弱的阻尼几乎被云辐射反馈的较弱维持所抵消，从而使线性湿度模式理论的增长率几乎不随变暖而变化。此外，估计的增长率被发现是一个小的，负值，这表明在模拟中的MJO是一个弱阻尼模式。Adames和Kim的水汽模式框架被用来理解MJO对GISS GCM中CO2增加的响应。水汽模式框架成功地预测了MJO的相速度随变暖的增加速率。在较暖的气候中，MJO的加速是由于平均状态、水汽对流耦合和MJO尺度的变化。
The processes that lead to changes in the propagation and maintenance of the Madden‐Julian Oscillation (MJO) as a response to increasing CO2 are examined by analyzing moist static energy budget of the MJO in a series of NASA GISS model simulations. It is found changes in MJO propagation is dominated by several key processes. Horizontal moisture advection, a key process for MJO propagation, is found to enhance predominantly due to an increase in the mean horizontal moisture gradients. The terms that determine the strength of the advecting wind anomalies, the MJO horizontal scale and the dry static stability, are found to exhibit opposing trends that largely cancel out. Furthermore, reduced sensitivity of precipitation to changes in column moisture, i.e., a lengthening in the convective moisture adjustment time scale, also opposes enhanced propagation. The dispersion relationship of Adames and Kim, which accounts for all these processes, predicts an acceleration of the MJO at a rate of ∼3.5% K−1, which is consistent with the actual phase speed changes in the simulation. For the processes that contribute to MJO maintenance, it is found that damping by vertical MSE advection is reduced due to the increasing vertical moisture gradient. This weaker damping is nearly canceled by weaker maintenance by cloud‐radiative feedbacks, yielding the growth rate from the linear moisture mode theory nearly unchanged with the warming. Furthermore, the estimated growth rates are found to be a small, negative values, suggesting that the MJO in the simulation is a weakly damped mode. The moisture mode framework of Adames and Kim is used to understand the MJO's response to increasing CO2 in the GISS GCM The moisture mode framework successfully predicts the rate of MJO's phase speed increase with the warming The acceleration of the MJO in a warmer climate is due to the changes in the mean state, moisture‐convection coupling, and the MJO's scale