Understanding Causes and Effects of Changes in the Atmospheric Circulation

随着人类活动使地球变暖，迫切需要了解对特定地区的影响。大气中的空气循环对区域气候有很大的影响：上升的空气通常会产生降水，而下降的空气通常非常干燥。随着地球变暖，大气环流的强度和空间结构正在发生变化，对降水和干燥的区域模式产生重要影响。关于造成这些环流变化的物理机制以及这些变化将在多大程度上影响区域气候，仍存在许多问题。因此，我提出了一个研究计划，以发展对这些机制的基本理解。这种理解将对气候模型产生宝贵的改进，并提高对气候模型预测的信心。在此资助期间，我提出的计划的主要目标是：目标1：检查循环机制驱动极端降水的长期变化，使用一个国家的最先进的高分辨率模型局限于128公里128公里的区域。这种配置使我们能够更好地控制区域模型的物理输入，从而产生新的发现，这些输入的特征对极端降水的区域变化最重要。目标二：比较观测估计和区域气候模式模拟中极端降水事件期间涡旋运动（"涡旋"）的空间结构。这项工作将对模型捕捉与真实的世界极端降水有关的大气环流关键特征的能力进行关键性检验。目标三：测试环流和降水变化对气候模式参数的敏感性，这些参数近似于称为“对流上升气流”的小尺度垂直运动。“当前一代的全球气候模型很难准确模拟对流上升气流的影响，我们的工作将发现模拟极端降水变化的可能后果。目标4：审查云和大气环流之间产生双向相互作用或"耦合"的机制。不同的气候模式产生不同的云-环流耦合强度，这反过来又强烈影响大气环流如何在空间中长期变化，对区域降水产生重要影响。这些目标是在区域气候变化模式预测方面取得变革性改进的重要步骤。我过去在这一领域的工作已经促进了与加拿大联邦和市政府的接触，加拿大国内外的一系列利益相关者（例如政策制定者，结构工程师，农业行业，保险公司）将感受到拟议工作的影响，这些利益相关者对预测和适应区域气候变化有着浓厚的兴趣。

As human activities warm the planet, there is an urgent need to understand the consequences for specific regions. Circulation of air in the atmosphere exerts a strong influence over regional climate: ascending air typically generates precipitation, whereas descending air is typically very dry. As the planet warms, the strength and spatial structure of the atmosphere's circulation is changing, with important consequences for regional patterns of precipitation and dryness. Many questions remain about the physical mechanisms responsible for these circulation changes and the extent to which these changes will influence regional climate. Thus, I am proposing a research program to develop the fundamental understanding of these mechanisms. Such understanding will produce valuable improvements in climate models and greater confidence in climate model projections. For this funding period, the key objectives of my proposed program are: Objective 1: Examine the circulation mechanisms driving long-term changes in extreme precipitation using a state-of-the-art high-resolution model confined to a 128 km by 128 km region. Such a configuration gives us more control over physical inputs to the regional model, thus generating new discoveries regarding what characteristics of those inputs are most consequential for regional changes of extreme precipitation. Objective 2: Compare the spatial structure of swirling motions ("eddies") during extreme precipitation events in observational estimates and simulations of regional climate models. Such work will provide a critical test of models' ability to capture key characteristics of the atmospheric circulation relevant for extreme precipitation in the real world. Objective 3: Test the sensitivity of circulation and precipitation changes to climate model parameters that approximate small-scale vertical motions called "convective updrafts." The current generation of global climate models struggle to accurately simulate the effects of convective updrafts, and our work will discover possible consequences for the simulation of extreme precipitation changes. Objective 4: Examine mechanisms that produce two-way interaction, or "coupling," between clouds and the atmospheric circulation. Different climate models produce different cloud-circulation coupling strength, and this in turn strongly influences how the atmospheric circulation shifts in space over the long-term, with important consequences for regional precipitation. These objectives serve as important steps towards making transformative improvements in model projections of regional climate change. My past work in this area has already stimulated engagement with federal and municipal government in Canada, and the impact of the proposed work will be felt by a range of stakeholders inside and outside Canada (e.g. policymakers, structural engineers, the agriculture industry, insurance companies) with strong interest in anticipating and adapting to regional climate change.