COntinental COnvective OrganisatioN and rainfall intensification in a warming world: Improving storm predictions from hours to decades (COCOON)

变暖世界中的大陆对流组织和降雨强度：将风暴预测从几小时提高到几十年（COCOON）

• 批准号: NE/X017419/1
• 负责人: Cornelia Klein
• 金额: $ 94.32万
• 依托单位: UK CENTRE FOR ECOLOGY & HYDROLOGY
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX017419%2F1
• 关键词: COntinental; COnvective; OrganisatioN; rainfall; intensification

Some of the most pressing questions in atmospheric and climate science today focus on how thunderstorms will respond to changes in the atmospheric environment. How will extreme rainfall change with climate change? And how do internal storm processes and dynamics affect these changes? Nowhere is the challenge more urgent than in (sub-)tropical regions where large thunderstorm clusters, so-called Mesoscale Convective Systems (MCSs) frequently cause severe weather and flooding, but population resilience is low due to poverty and staggering economies. To estimate and plan for future storm impacts, we need to understand and model how storm dynamics will respond (and are already responding) to atmospheric changes, and whether there are internal, dynamical mechanisms that may intensify rainfall extremes beyond purely thermodynamical considerations linked to increased moisture in a warmer atmosphere. In most affected regions, MCSs provide crucial water supplies for crops, livestock and people, contributing 50-90% to total rainfall but are likewise associated with severe weather that affects millions around the globe. A situation that will only worsen as temperatures continue to rise. And yet, in spite of the societal importance of MCSs, we still do not know why in particular their sub-daily rainfall extremes can frequently surpass expected intensities. The fact that the relative importance of external (e.g. atmospheric humidity, wind shear, temperature) and internal drivers (storm circulations, updraught speeds and size) of rainfall maxima remain unclear also hampers our ability to estimate global warming effects. Climate model assessments of driver contributions so far do not exist as conventional global climate models with coarse resolutions ~100km have major difficulties representing processes in the MCS scale range, which they can neither explicitly resolve nor satisfactorily parametrise, i.e. they do not 'see' MCSs. Over the last decade however, there have been rapid advances in the use of high-resolution (<10 km) regional convection-permitting (CP) models for climate prediction. Not having to rely on convective parametrisations, CP models produce more realistic peak rainfall intensities even compared to medium-resolution models, and can simulate realistic MCSs. However, even state-of-the-art CP models still operate in the "grey-zone" of 1-10km where internal storm circulations are only partly resolved. Consequences of the neglect of sub-grid processes are still under investigation and shortcomings need to be put under scrutiny.By combining earth observation data with emerging state-of-the-art CP climate model simulations, my project investigates how the scale of convection (contiguous cloud shields, embedded convective core scales, updraught size) affects MCS rainfall extremes and lifetimes over land. Based on earth observation data, my work will discover whether scales of continental convective organisation have changed within the last 20-30 years, and what processes are key to determining such trends. This will also explore whether MCS interactions with land features and atmospheric environments change as a function of convective scale. I will furthermore challenge CP models with the identified processes and develop process-based model benchmarking approaches, testing how trustworthy CP models are in capturing rainfall intensification mechanisms in a future climate. The findings will be used to trial methods for improved storm nowcasting and for improved estimates of future MCS rainfall extremes based on multiple lines of evidence that will crucially include convective scales. Thus, my project will bring a step-change in our understanding of how global warming drives convective scale changes, how rainfall and scales are linked, and whether scale information can improve extreme rainfall predictions on weather to climate timescales.

当今大气和气候科学中一些最紧迫的问题集中于雷暴将如何应对大气环境的变化。气候变化会如何变化？内部风暴过程和动态如何影响这些变化？没有比在（亚）热带地区更紧迫的挑战，在这些地区，大型雷暴群集，所谓的中尺度对流系统（MCS）经常造成恶劣的天气和洪水，但由于贫困和惊人的经济体，人口弹性较低。为了估计和计划未来的风暴影响，我们需要了解并模拟风暴动态如何应对大气变化（并且已经在响应）对大气变化的反应，以及是否存在内部动力学机制，这些机制是否会加剧极端降雨量，而不是纯粹的热力学考虑因素，与较温暖的大气中的水分增加有关。在大多数受影响的地区，MCS为农作物，牲畜和人们提供关键的水供应，对总降雨贡献了50-90％，但同样与恶劣天气有关，这会影响全球数百万。随着温度继续升高，这种情况只会加剧。然而，尽管MCS具有社会重要性，但我们仍然不知道为什么特别是他们的每日降雨极端经常超过预期的强度。外部（例如大气湿度，风剪，温度）和内部驱动因素（风暴循环，上升速度和大小）的相对重要性仍然不清楚，这一事实尚不清楚，也妨碍了我们估计全球变暖效应的能力。到目前为止，驾驶员贡献的气候模型评估尚未存在，因为〜100公里的常规全球气候模型在MCS量表范围内代表过程中遇到了重大困难，它们既不能明确解决也不令人满意地参数，即他们没有“参见” MCSS。然而，在过去的十年中，使用高分辨率（<10 km）区域对流 - 渗透模型（CP）模型来进行气候预测，这一进步迅速。 CP模型不必依靠对流参数，即使与中分辨率模型相比，CP模型也会产生更现实的峰值降雨强度，并可以模拟现实的MCS。但是，即使是最先进的CP模型仍在1-10公里的“灰区”中运行，其中内部风暴循环仅部分解决。 Consequences of the neglect of sub-grid processes are still under investigation and shortcomings need to be put under scrutiny.By combining earth observation data with emerging state-of-the-art CP climate model simulations, my project investigates how the scale of convection (contiguous cloud shields, embedded convective core scales, updraught size) affects MCS rainfall extremes and lifetimes over land.根据地球观察数据，我的工作将发现大陆对流组织的量表在过去20 - 30年内是否发生了变化，哪些过程是确定此类趋势的关键。这还将探索MCS与土地特征和大气环境的相互作用是否随对流量表的函数而变化。我将使用确定的过程挑战CP模型并开发基于过程的模型基准方法，并测试值得信赖的CP模型在未来气候下捕获降雨强化机制时如何捕获降雨。这些发现将用于试验改善风暴象征的方法，并根据多种证据，对未来MCS极端的估计进行了改进，这些证据将包括至关重要的对流量表。因此，我的项目将使我们对全球变暖驱动器如何变化，降雨量和规模的联系以及规模信息是否可以改善天气对气候时间标准的极端降雨预测的理解，使对流量表变化，降雨量和规模如何变化，对对流量表的变化发生变化，降雨量和规模如何变化。