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区域的影响。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，对区域降水和干旱模式产生了重要影响。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，仍然存在许多问题。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。这样的理解将对气候模型产生有价值的改进，并对气候模型预测产生更大的信心。在这一资助期内，我提议的方案的主要目标是：目标1：利用限制在128公里乘128公里区域的最先进的高分辨率模式，研究驱动极端降水长期变化的环流机制。这样的配置使我们对区域模式的物理输入有了更多的控制，从而产生了关于这些输入的哪些特征对区域极端降水变化最重要的新发现。目的2：在区域气候模式的观测估计和模拟中，比较极端降水事件期间涡旋运动(“涡”)的空间结构。这项工作将对模型捕捉与现实世界极端降水有关的大气环流关键特征的能力进行关键测试。目标3：测试环流和降水变化对气候模式参数的敏感度，气候模式参数近似于称为“对流上升气流”的小尺度垂直运动。当前一代的全球气候模式难以准确模拟对流上升气流的影响，我们的工作将发现极端降水变化模拟可能产生的后果。目标4：研究在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在长期内如何在空间转移，从而对区域降水产生重要影响。这些目标是对区域气候变化模型预测作出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攸关方(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，他们对预测和适应区域气候变化有着强烈的兴趣。

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.