Breaking the tropical convection "dead-lock": Scale interactions of deep convection and tropical circulation

打破热带对流“僵局”：深层对流与热带环流的尺度相互作用

• 批准号: 2743337
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2743337
• 关键词: Breaking; tropical; convection; dead; lock

This project will analyse the properties of tropical convective storms and larger-scale tropical waves, in state of the art models and in observations. The work will advance our understanding of the Earth's climate system, through analysis of scale interactions in tropical atmospheric dynamics. Working closely with the Met Office and making use of their new "k-scale" modelling capability, we will address long-standing problems in the understanding of climate circulation. The interaction of moist convection with larger-scale circulations is a limiting factor for predictions across time scales. The coupling of convection with circulation under climate change is highlighted as a grand challenge in the "Clouds, Circulation and Climate Sensitivity" Grand Challenge of the World Climate Research programme (WCRP). Past projects have shown the value of explicitly modelling convection over large domains in allowing new insights to this difficult problem. The tropics are the "engine room" of Earth's climate: solar heating is maximised in equatorial regions at the land and ocean surface, and transmitted higher into the atmosphere by convection. Tropical convection is dominated by cumulonimbus storms that not only deliver rainfall, but generate intense atmospheric heating, which is then communicated to the wider atmosphere by waves. For decades the representation of these moist convective storms has provided a "deadlock" in weather and climate modelling, as it has been impossible to model them directly in a global model due to their small scale. This is one major reason why skill of numerical weather prediction is low in the tropics, and climate change projections of rainfall are very uncertain, for major climatic systems like the monsoons. Increased computer power is now removing this "dead-lock". Tropical convection is intrinsically chaotic, but some predictability and organisation of the convection is provided by larger-scale propagating waves, by interaction with continental-scale circulations such as monsoons, and through processes at the land and sea surface. Understanding how moist convection interacts with larger scale flows is made much more challenging by the fact that the cumulonimbus storms that generate ascent and rainfall in the tropics are not explicitly resolved in global models, which have grid-spacings of approximately 10s or 100s of kilometres. This means their effects are normally represented by simplifications known as parametrisations, which lead to significant errors in the way that storms interact with their environment. For the first time, computational power enables us to run global or pan-tropical simulations that have a small enough grid-spacing (approximately 1 to 5 km) to explicitly capture these storms.The project will address the following scientific objectives:(1) How moist convection interacts with tropical waves, how this is affected by the representation of convection, and the implications for predictions.(2) How moist convection influences the water and energy balance of large regions.(3) Evaluating the role of clouds and convective processes in a changing climate.We anticipate that the work will include:Analysis of cloud and storm properties in the k-scale simulations, and their relationship to "drivers" in large-scale winds and thermodynamics;Comparison of modelled behaviour with satellite and surface-based observations;Diagnosis of tropical wave modes and their modulation by the convection;Use of properties such as vorticity to quantify "scale interactions" between convection and waves;Focus on key aspects of storm life-cycles, such as initiation, intensification, propagation and circulation.The results will guide the development and use of the weather and climate prediction models of the future. By capitalising on unique new simulations from the Met Office's operational model.

该项目将在最先进的模式和观测中分析热带对流风暴和较大规模热带波的特性。这项工作将通过分析热带大气动力学中的尺度相互作用，促进我们对地球气候系统的理解。我们将与气象局密切合作，利用他们新的“k尺度”模拟能力，解决长期存在的气候环流理解问题。湿对流与更大尺度环流的相互作用是跨时间尺度预测的限制因素。在世界气候研究计划的“云、环流和气候敏感性”大挑战中，气候变化下的对流与环流的耦合被强调为一项重大挑战。过去的项目已经显示了对大区域对流进行明确建模的价值，这使得人们能够对这个难题有新的见解。热带地区是地球气候的“引擎室”：陆地和海洋表面的赤道地区的太阳热量最大，并通过对流传播到更高的大气中。热带对流以积雨云风暴为主，它们不仅提供降雨，而且产生强烈的大气加热，然后通过波浪传递到更广泛的大气。几十年来，这些潮湿对流风暴的表现在天气和气候模拟方面造成了“僵局”，因为由于其规模较小，不可能直接在全球模式中对它们进行模拟。这是热带地区数值天气预报技术低的一个主要原因，对于季风等主要气候系统来说，对降雨量的气候变化预测非常不确定。增强的计算机能力现在正在消除这种“死锁”。热带对流本质上是混乱的，但一些对流的可预测性和组织是由更大规模的传播波提供的，通过与季风等大陆尺度环流的相互作用，以及通过陆地和海洋表面的过程。由于在全球模式中没有明确地解决在热带产生上升和降雨的积雨云风暴这一事实，理解湿对流如何与更大规模的气流相互作用变得更加困难，因为全球模式的网格间距约为10s或100s公里。这意味着它们的影响通常表现为被称为参数调整的简化，这会导致风暴与环境相互作用的方式出现重大错误。计算能力首次使我们能够运行具有足够小的网格间距(大约1到5公里)的全球或泛热带模拟来明确地捕捉这些风暴。该项目将解决以下科学目标：(1)湿对流如何与热带波相互作用，对流的表示如何影响这一相互作用，以及对预报的影响。(2)湿对流如何影响大区域的水和能量平衡。(3)评估云和对流过程在变化的气候中的作用。我们预计这项工作将包括：在k尺度模拟中分析云和风暴的特性，以及它们与大尺度风和热力学中的“驱动力”的关系；模拟的行为与卫星和地面观测的比较；热带波模式的诊断和对流对它们的调制；利用涡度等属性来量化对流和波之间的“尺度相互作用”；重点关注风暴生命周期的关键方面，如启动、加强、传播和环流。结果将指导未来天气和气候预测模型的开发和使用。通过利用英国气象局运营模型中独特的新模拟。