Convective storms, tropical circulation and climate change

这是一个数学和理论项目，将探索强风暴和大气大范围环流之间的关系。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不确定的因素之一。在印度和非洲等人口众多、易受气候波动影响的地区，对热带大陆降雨量的数值预测存在很大误差。我们将首先使用经典的Rayleigh-Benard对流模型，该模型经过修改，包含了多云大气对流的简单表示(Rainy-Benard，RYB)，以探索更深层次的问题。这个简单的“Rainy-Benard”问题分享了真实热带对流中的一些特征，并将使我们能够探索基本的数学控制对流-环流相互作用。RYB的预算和均衡状态是什么？它们如何应对边界条件的变化(如热辐射、海面温带或土地利用等气候变化压力)？在表示陆地和海洋上的对流和降雨时，是否存在地区差异？我们将利用英国气象局业务天气和气候预测模型的新一代非常高分辨率的大气模拟，来测试从RYB发展起来的理论。这些模型模拟将用于测试和改进我们的数学模型，并描述几公里尺度的云中潜热如何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，并有机会定期访问气象局。该项目还将受益于与几个英国和国际项目的联系，我们是这些项目的合作伙伴，例如EUREC4A。项目的主要成果将是从理论上更好地理解云潜热函数在热带对流场中的作用，以及这种作用如何影响对流驱动大尺度环流并与之相互作用的能力。这些知识是理解气候系统对其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，它将影响围绕区域气候变化的政策和决策。预计这项工作将涉及以下活动：Rainy-Benard系统中理论对流系统的理想化模拟。理想化模拟的扩展，以考虑物理过程，例如：行星自转；辐射冷却；蒸发冷却；可变表面条件；或与热带波和急流的相互作用。对允许对流的统计特性的量化分析。使用相同的理论框架，对热带对流的模拟(例如平衡和能量收支)。探索使用机器学习来估计统计特性的参数的潜力。分析理论/理想化和允许对流的模型的低分辨率版本，导致建议在低分辨率气候模式中更好地表示对流。

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.