A ∼50 km resolution atmospheric general circulation model (GCM) is used to investigate the impact of radiative interactions on spatial organization of convection, the model's mean state, and extreme precipitation events in the presence of realistic boundary conditions. Mechanism-denial experiments are performed in which synoptic-scale feedbacks between radiation and dynamics are suppressed by overwriting the model-generated atmospheric radiative cooling rates with its monthly varying climatological values. When synoptic-scale radiative interactions are disabled, the annual mean circulation and precipitation remain almost unchanged, however tropical convection becomes less aggregated, with an increase in cloud fraction and relative humidity in the free troposphere but a decrease in both variables in the boundary layer. Changes in cloud fraction and relative humidity in the boundary layer exhibit more sensitivity to the presence of radiative interactions than variations in the degree of aggregation. The less aggregated state is associated with a decrease in the frequency of extreme precipitation events, coincident with a decrease in the dynamical contribution to the magnitude of extreme precipitation. At regional scales, the spatial contrast in radiative cooling between dry and moist regions diminishes when radiative interactions are suppressed, reducing the upgradient transport of energy, degree of aggregation, and frequency of extreme precipitation events. However, the mean width of the tropical rain belt remains almost unaffected when radiative interactions are disabled. These results offer insights into how radiation-circulation coupling affects the spatial organization of convection, distributions of clouds and humidity, and weather extremes.

中文翻译：

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调查高分辨率大气 GCM 中对流聚集的原因和影响

约 50 公里分辨率的大气环流模型 (GCM) 用于研究辐射相互作用对对流的空间组织、模型的平均状态和存在现实边界条件的极端降水事件的影响。进行了机制否认实验，其中通过用每月变化的气候值覆盖模型生成的大气辐射冷却速率来抑制辐射和动力学之间的天气尺度反馈。当天气尺度辐射相互作用被禁用时，年平均环流和降水几乎保持不变，但热带对流变得不那么聚集，自由对流层的云量和相对湿度增加，但边界层中的两个变量都减少。边界层中云量和相对湿度的变化对辐射相互作用的存在比聚集程度的变化更敏感。较少聚集状态与极端降水事件频率的减少有关，同时与对极端降水量级的动力学贡献的减少相一致。在区域尺度上，当辐射相互作用被抑制时，干燥和潮湿区域之间辐射冷却的空间对比度会减小，从而减少能量的上升传输、聚集程度和极端降水事件的频率。然而，当辐射相互作用被禁用时，热带雨带的平均宽度几乎不受影响。