Robust atmospheric river response to global warming in idealized and comprehensive climate models
Robust atmospheric river response to global warming in idealized and comprehensive climate models
复制标题
理想化综合气候模型中大气河流对全球变暖的稳健响应
DOI：
10.1175/jcli-d-20-1005.1
复制
发表时间：
2021
影响因子：
4.9
通讯作者：
Wu, Zheng
中科院分区：
文献类型：
--
作者：
Zhang, Pengfei;Chen, Gang;Ma, Weiming;Ming, Yi;Wu, Zheng
大气河流（ARs）是一种狭窄的强水汽输送，在中纬度地区的极向水汽输送中占了很大的比重。虽然研究已经在观测和综合气候模式中描述了AR特征和相关的气候变暖水文影响，但AR统计变化的基本动态（如频率、长度、宽度）尚未得到很好的理解。在这里，我们研究了AR对全球变暖的响应，结合了理想和综合气候模式。为此，我们开发了一个理想化的大气GCM，具有类似地球的全球环流和水文循环，其中水蒸气和云被模拟为具有简单云微物理和降水过程的被动示踪剂。尽管模型物理简单，但它合理地再现了观测到的单个AR的动力结构、AR的统计特征和AR气候学的空间分布。在气候变暖条件下，理想模式产生的AR变化与RCP8.5下CESM大集合模拟结果相似，包括AR尺寸扩大、登陆水汽输送增强和AR频率增加，证实了气候模式先前报道的全球变暖条件下AR变化。此外，随着气候变暖，AR频率最大值的纬度向极地移动。进一步分析表明，热力效应（即水汽增加）主导了AR统计和频率变化，而动力效应和热力效应都有助于AR向极移。这些结果表明，气候变暖的AR变化可以理解为受大尺度大气环流调节的被动水蒸气和云示踪剂，而对流和潜热反馈则是次要的。
Atmospheric rivers (ARs), narrow intense moisture transport, account for much of the poleward moisture transport in midlatitudes. While studies have characterized AR features and the associated hydrological impacts in a warming climate in observations and comprehensive climate models, the fundamental dynamics for changes in AR statistics (e.g., frequency, length, width) are not well understood. Here we investigate AR response to global warming with a combination of idealized and comprehensive climate models. To that end, we developed an idealized atmospheric GCM with Earth-like global circulation and hydrological cycle, in which water vapor and clouds are modeled as passive tracers with simple cloud microphysics and precipitation processes. Despite the simplicity of the model physics, it reasonably reproduces observed dynamical structures for individual ARs, statistical characteristics of ARs, and spatial distributions of AR climatology. Under climate warming, the idealized model produces robust AR changes similar to CESM large ensemble simulations under RCP8.5, including AR size expansion, intensified landfall moisture transport, and an increased AR frequency, corroborating previously reported AR changes under global warming by climate models. In addition, the latitude of AR frequency maximum shifts poleward with climate warming. Further analysis suggests that the thermodynamic effect (i.e., an increase in water vapor) dominates the AR statistics and frequency changes while both the dynamic and thermodynamic effects contribute to the AR poleward shift. These results demonstrate that AR changes in a warming climate can be understood as passive water vapor and cloud tracers regulated by large-scale atmospheric circulation, whereas convection and latent heat feedback are of secondary importance.