Congestus Mode Invigoration by Convective Aggregation in Simulations of Radiative-Convective Equilibrium.
Congestus Mode Invigoration by Convective Aggregation in Simulations of Radiative-Convective Equilibrium.
复制标题
在辐射-对流平衡模拟中对流聚合对密集模的激发。
DOI：
10.1029/2022ms003045
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发表时间：
2022-07
影响因子：
6.8
通讯作者：
Hartmann, Dennis L.
中科院分区：
文献类型：
--
作者：
Sokol, Adam B.;Hartmann, Dennis L.
关键词：
本文研究了热带对流的拥堵模式在辐射-对流平衡(RCE)数值模拟中的表现。我们从参与RCE模型对比项目(RCEMIP)的云解析模型集合和一个新的二维RCE模拟集合中获得了见解。大约一半的RCEMIP模式产生了不同于深部和浅部模式的拥挤环流。在这两个集合中，稠密环流随着大尺度对流聚集而增强，而在2D集合中，这是以以边界层顶部为中心的浅环流为代价的。由于凝结使对流层上层干燥，从而使潮湿的拥堵气流经历强烈的辐射冷却，因此发生了拥堵增强。降温会产生分歧，促进持续的充血颠覆(积极的反馈)。这一机制与地面边界层顶部辐射冷却驱动浅层环流基本相似。凝结和拥堵增强也与整个对流层静力稳定性的增强有关，但模拟试验表明，增强稳定性并不是拥堵增强所必需的；相反，增强本身通过影响辐射冷却的垂直廓线而有助于稳定度的增加。如前所述，卷吸冷却的变化也被发现在增强稳定性方面起着重要作用。当存在时，拥挤环流对平均RCE大气状态有很大的影响；因此，它们在模式中的不一致表示以及它们对真实热带大气的影响值得进一步研究。RCE中拥堵模式的表示在不同模式之间有很大差异。拥堵模式被大尺度对流聚集所激活对流层稳定性因拥堵增强和卷吸冷却减少而随着聚集而增加
This study examines how the congestus mode of tropical convection is expressed in numerical simulations of radiative‐convective equilibrium (RCE). We draw insights from the ensemble of cloud‐resolving models participating in the RCE Model Intercomparison Project (RCEMIP) and from a new ensemble of two‐dimensional RCE simulations. About half of the RCEMIP models produce a congestus circulation that is distinct from the deep and shallow modes. In both ensembles, the congestus circulation strengthens with large‐scale convective aggregation, and in the 2D ensemble this comes at the expense of the shallow circulation centered at the top of the boundary layer. Congestus invigoration occurs because aggregation dries out the upper troposphere, which allows moist congestus outflow to undergo strong radiative cooling. The cooling generates divergence that promotes continued congestus overturning (a positive feedback). This mechanism is fundamentally similar to the driving of shallow circulations by radiative cooling at the top of the surface boundary layer. Aggregation and congestus invigoration are also associated with enhanced static stability throughout the troposphere, but a modeling experiment shows that enhanced stability is not necessary for congestus invigoration; rather, invigoration itself contributes to the stability increase via its impact on the vertical profile of radiative cooling. Changes in entrainment cooling are also found to play an important role in stability enhancement, as has been suggested previously. When present, congestus circulations have a large impact on the mean RCE atmospheric state; for this reason, their inconsistent representation in models and their impact on the real tropical atmosphere warrant further scrutiny. Representation of the congestus mode in RCE varies greatly across models The congestus mode is invigorated by large‐scale convective aggregation Tropospheric stability increases with aggregation due to congestus invigoration and reduced entrainment cooling