Physical mechanisms controlling the initiation of convective self‐aggregation in a General Circulation Model
Physical mechanisms controlling the initiation of convective self‐aggregation in a General Circulation Model
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大气环流模型中控制对流自聚集引发的物理机制
DOI：
10.1002/2015ms000571
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发表时间：
2015
影响因子：
6.8
通讯作者：
S. Bony
中科院分区：
文献类型：
--
作者：
D. Coppin;S. Bony
云分辨模式表明，在一定条件下，辐射-对流平衡(RCE)可能变得不稳定，导致大气自发组织成干湿区，并导致对流聚集。在这项研究中，我们表明，这种“自聚集”行为也出现在用IPSL-CM5A-LR大气环流模式(GCM)进行的非旋转RCE模拟中，并且这种“自聚集”行为表现出对海表面温度(SST)的强烈依赖。我们研究了在该模型中控制自聚集启动的物理机制，以及它们对温度的依赖。在低海温时，自聚集的开始主要受低云辐射效应和浅层环流的耦合以及在无深对流的地区形成“辐射驱动冷池”的控制，而在高海温时，主要受对流区内地面通量和环流之间的耦合控制。在中等温度下，自聚集的发生不那么自发，并且取决于初始条件，但它可以通过这两种机制的组合而发生。通过与环流和地面通量的耦合，低层云的辐射效应在这两种启动机制中都起着关键作用，边界层云对地面温度的敏感性在很大程度上解释了对流自聚集的温度依赖性。在任何SST，自由对流层中云辐射效应的存在对于对流聚集的启动、增长和维持都是必要的。
Cloud‐resolving models have shown that under certain conditions, the Radiative‐Convective Equilibrium (RCE) could become unstable and lead to the spontaneous organization of the atmosphere into dry and wet areas, and the aggregation of convection. In this study, we show that this “self‐aggregation” behavior also occurs in nonrotating RCE simulations performed with the IPSL‐CM5A‐LR General Circulation Model (GCM), and that it exhibits a strong dependence on sea surface temperature (SST). We investigate the physical mechanisms that control the initiation of self‐aggregation in this model, and their dependence on temperature. At low SSTs, the onset of self‐aggregation is primarily controlled by the coupling between low‐cloud radiative effects and shallow circulations and the formation of “radiatively driven cold pools” in areas devoid of deep convection, while at high SSTs it is primarily controlled by the coupling between surface fluxes and circulation within convective areas. At intermediate temperatures, the occurrence of self‐aggregation is less spontaneous and depends on initial conditions, but it can arise through a combination of both mechanisms. Through their coupling to circulation and surface fluxes, the radiative effects of low‐level clouds play a critical role in both initiation mechanisms, and the sensitivity of boundary layer clouds to surface temperature explains to a large extent the temperature dependence of convective self‐aggregation. At any SST, the presence of cloud‐radiative effects in the free troposphere is necessary to the initiation, growth, and maintenance of convective aggregation.
影响因子：
6.8
作者：
Tobin I
通讯作者：
Tobin I