The sensitivity of convective aggregation to diabatic processes in idealized radiative-convective equilibrium simulations
The sensitivity of convective aggregation to diabatic processes in idealized radiative-convective equilibrium simulations
复制标题
理想化辐射对流平衡模拟中对流聚集对非绝热过程的敏感性
DOI：
10.1002/2015ms000511
复制
发表时间：
2016
影响因子：
6.8
通讯作者：
Holloway C
中科院分区：
文献类型：
--
作者：
Holloway C
英国气象局统一模型的理想化显式对流模拟在辐射对流平衡中表现出自发的自聚集，如在先前研究的其他模型中所见。这种自聚集与辐射、地面通量和对流之间的反馈有关，并且这种组织与柱水汽场的演变密切相关。根据Wing和Emanuel（2014），对柱积分冻结湿静力能（MSE）的空间方差的预算进行分析，揭示了直接辐射反馈（包括显着的云长波效应）在自聚集的初始发展和聚集状态的维持中占主导地位。在聚合的中间阶段，低层环流似乎确实将MSE从干燥地区输送到潮湿地区，但这种环流主要是由其他相反符号的平流效应平衡的，并且是由对流加热（而不是辐射）的水平异常强迫的。对于固定的辐射冷却、固定的表面通量或两者的敏感性研究都没有显示出从均匀初始条件的完全自聚集，尽管固定的表面通量不会分解初始化的聚集状态。一项敏感性研究显示，关闭雨水蒸发的自聚集速度更快，而这种变化加上固定的辐射冷却仍然显示出强烈的自聚集，支持Muller和Bony（2015）中发现的"水分记忆"效应。有趣的是，即使在295和290 K的海面温度（SST）模拟中也会发生自聚集，直接辐射反馈主导MSE方差的预算，与以前的一些研究结果相反。
Idealized explicit convection simulations of the Met Office Unified Model exhibit spontaneous self‐aggregation in radiative‐convective equilibrium, as seen in other models in previous studies. This self‐aggregation is linked to feedbacks between radiation, surface fluxes, and convection, and the organization is intimately related to the evolution of the column water vapor field. Analysis of the budget of the spatial variance of column‐integrated frozen moist static energy (MSE), following Wing and Emanuel (2014), reveals that the direct radiative feedback (including significant cloud longwave effects) is dominant in both the initial development of self‐aggregation and the maintenance of an aggregated state. A low‐level circulation at intermediate stages of aggregation does appear to transport MSE from drier to moister regions, but this circulation is mostly balanced by other advective effects of opposite sign and is forced by horizontal anomalies of convective heating (not radiation). Sensitivity studies with either fixed prescribed radiative cooling, fixed prescribed surface fluxes, or both do not show full self‐aggregation from homogeneous initial conditions, though fixed surface fluxes do not disaggregate an initialized aggregated state. A sensitivity study in which rain evaporation is turned off shows more rapid self‐aggregation, while a run with this change plus fixed radiative cooling still shows strong self‐aggregation, supporting a “moisture‐memory” effect found in Muller and Bony (2015). Interestingly, self‐aggregation occurs even in simulations with sea surface temperatures (SSTs) of 295 and 290 K, with direct radiative feedbacks dominating the budget of MSE variance, in contrast to results in some previous studies.