Global-scale convective aggregation: Implications for the Madden-Julian Oscillation
Global-scale convective aggregation: Implications for the Madden-Julian Oscillation
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DOI：
10.1002/2015ms000498
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发表时间：
2015-12-01
影响因子：
6.8
通讯作者：
Randall, David A.
中科院分区：
文献类型：
--
作者：
Arnold, Nathan P.;Randall, David A.
先前的工作表明，对流会在辐射对流平衡的云系统解析模型模拟中自组织，并且有人提出，马登-朱利安振荡（MJO）的对流包络线可能会通过更大范围内的类似过程来组织。在这里，我们基于具有全局统一 SST 的 SP-CAM 模拟来支持该假设。在没有旋转的情况下，对流会自组织成被干燥区域包围的大型（约 4000 公里）簇，而在类似地球的旋转下，该模型会产生强大的 MJO。人们发现非旋转聚集和 MJO 具有相似的湿静态能量预算，两者都受到非绝热反馈的支持，特别是云-长波相互作用。机制否认实验表明，与高云相关的长波加热异常对于非旋转聚集至关重要，并放大了 MJO。使用传统 CAM 进行的模拟显示，MJO 较弱，非旋转聚集趋势也较弱，并且发现 MJO 活性和聚集强度都随着深对流参数化中夹带率的增加而增加。
Previous work has shown that convection will self-organize in cloud-system-resolving model simulations of radiative-convective equilibrium, and it has been suggested that the convective envelope of the Madden-Julian oscillation (MJO) may be organized by similar processes on a much larger scale. Here we present support for that hypothesis based on simulations with SP-CAM with globally uniform SST. Without rotation, convection self-organizes into large (approximate to 4000 km) clusters surrounded by dry regions, while with Earth-like rotation the model produces a robust MJO. The nonrotating aggregation and MJO are found to have similar budgets of moist static energy, both being supported by diabatic feedbacks, particularly cloud-longwave interaction. Mechanism denial experiments show that longwave heating anomalies associated with high clouds are essential to the nonrotating aggregation, and amplify the MJO. Simulations using the conventional CAM show a weaker MJO and a much weaker tendency for nonrotating aggregation, and both MJO activity and aggregation intensity are found to increase with the entrainment rate in the deep convection parameterization.