Convective storms, tropical circulation and climate change

这是一个数学和理论项目，将探索严重风暴和大气中大规模环流之间的关系。对流风暴主导着热带地区的能量平衡，但它们与环流的耦合是全球预测中最重要的不确定性之一。热带大陆降雨的数值预测有很大的误差，在印度和非洲等地区，大量人口容易受到气候波动的影响。我们将首先使用经典的Rayleigh-Benard对流模型，修改为包括多云大气对流的简单表示（“Rainy-Benard”，RyB），以探索深层次的问题。这个简单的“Rainy-Benard”问题具有真实的热带对流中的一些特征，并将使我们能够探索对流-环流相互作用的基本数学控制。RyB的预算和平衡状态是什么？这些是如何对边界条件的变化（气候变化强迫，如热辐射、海面温度或土地使用）作出反应的？在表示陆地和海洋上的对流和降雨时，是否存在区域差异？我们将利用新一代非常高分辨率的大气模拟与气象局的业务天气和气候预测模型，以测试从RyB开发的理论。这些模型模拟将用于测试和改进我们的数学模型，并描述云的潜热加热如何在几公里的尺度上影响数千公里尺度上大陆和海洋的降雨模式。我们与英国气象局建立了合作伙伴关系，该项目将与那里的同事合作进行，有机会定期访问气象局。该项目还将受益于与我们合作的几个英国和国际项目的联系，例如EUREC 4A。该项目的主要成果将是从理论上更好地了解云潜热加热功能在热带对流场中的作用，以及这种功能如何影响对流驱动大规模环流并与之相互作用的能力。这方面的知识是了解气候系统对气候边界条件变化的反应方式所必需的。最终，如果这项工作取得成功，它将影响有关区域气候变化的政策和决策。预计这项工作将涉及下列活动：Rainy-Benard系统理论对流状态的理想化模拟;理想化模拟的扩展，以考虑物理过程，如：行星旋转;辐射冷却;蒸发冷却;可变表面条件;对流允许模式模拟热带对流的统计特性的定量分析（例如平衡和能量收支），使用相同的理论框架。探索使用机器学习进行统计特性参数估计的潜力。分析理论/理想化和对流允许模式的低分辨率版本，从而为未来在低分辨率气候模式中更好地表示对流提出建议。

This is a mathematical and theoretical project which will explore the relationship between severe storms and large-scale circulation in the atmosphere. Convective storms dominate the energy balance of the tropics, but their coupling with the circulation represents one of the foremost uncertainties in global prediction. Numerical predictions of rainfall over the tropical continents have substantial errors, in regions such as India and Africa where large populations are vulnerable to fluctuations in the climate.We will first use the classic Rayleigh-Benard convection model, modified to include a simple representation of cloudy atmospheric convection ("Rainy-Benard", RyB), to explore deep questions. This simple "Rainy-Benard" problem shares a number of characteristics seen in real tropical convection, and will allow us to explore the underlying mathematical controls convection-circulation interaction. What are the budgets and equilibrium states of RyB? How do these respond to changes in boundary conditions (climate-change forcings like thermal radiation, sea surface temperate or land use)? Are there regional differences, when representing convection and rainfall over land and sea?We will exploit the new generation of very high-resolution atmospheric simulations with the Met Office's operational weather and climate prediction model, to test the theories developed from RyB. These model simulations will be used to test and refine our mathematical models and describe the ways in which latent heating in clouds, on scales of a few kilometres, influences patterns of rainfall over continents and oceans on scales of many thousand kilometres.We have an established partnership with the UK Met Office, and this project will be conducted in collaboration with colleagues there, with opportunities to visit the Met Office periodically. The project will also benefit from links with several UK and international projects in which we are partners, such as EUREC4A. The primary project outcome will be improved theoretical understanding of the role of cloud latent heating functions in fields of tropical convection, and the way in which this influences the capacity of the convection to drive and interact with large-scale circulations. This knowledge is needed to understand the way in which the climate system responds to changes in its climatic boundary conditions. Ultimately, if the work is successful, it will influence policy and decision-making around regional climate change. It is expected that the work will involve the following activities.Idealised modelling of theoretical convective regimes in the Rainy-Benard system.Extension of the idealised modelling to consider physical processes such as: planetary rotation; radiative cooling; evaporative cooling; variable surface conditions; or interaction with tropical waves and jets.Quantitative analysis of statistical properties of convection-permitting model simulations of tropical convection (e.g. equilibria and energy budgets), using the same theoretical framework.Potential to explore the use of machine learning for parameter estimation of statistical properties.Analysis of low-resolution versions of both the theoretical/idealised and convection-permitting models, leading to recommendations for better future representation of convection in low-resolution climate models.