Land Impacts on Mesoscale Convective Systems

土地对中尺度对流系统的影响

• 批准号: NE/W001888/1
• 负责人: Christopher Taylor
• 金额: $ 92.19万
• 依托单位: UK CENTRE FOR ECOLOGY & HYDROLOGY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 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=NE%2FW001888%2F1
• 关键词: Land; Impacts; Mesoscale; Convective; Systems

Mesoscale Convective Systems (MCSs) are among the most powerful storms in the world, and in many places are the dominant cause of hazards such as high winds, lightning, flash flooding and tornadoes. Across the tropics, MCSs account for 80% of extreme rainfall days. They result from thunderstorms that organize into a single large complex hundreds of km wide, which travel across the land for hours, in some cases days, causing extraordinary downpours along their path. They are particularly prevalent in certain "hotspot" regions including Northern Argentina and India, West and Central Africa, and the US Great Plains, where a combination of warm, moist air and favourable winds support their development. In these hotspot regions, an understanding of how MCSs will change as the world warms is urgently needed in order to build climate-resilient homes, roads, bridges and dams. Conventional climate models lack sufficient spatial resolution to realistically simulate these storms. There has however been a revolution in high-resolution climate models over the past 5 years, enabled by increasing computer power. New "Convection Permitting Models" (CPMs) can represent MCSs and are starting to deliver improved predictions and better understanding of how MCSs respond to their environment.We know that spatial patterns in vegetation and soil humidity affect air temperature, moisture and wind flows, and that these changes can affect where (or indeed whether) a powerful MCS develops. For example, contrasts between tropical forests and deserts control surface temperature differences across the continents, creating MCS hotspot regions through favourable wind conditions. Those surface temperature differences are already increasing due to global warming, and have been implicated in a tripling of the most intense West African MCSs over just 35 years, contributing to a dramatic rise in flash flooding there. We also know that the land surface affects individual MCS tracks. Evidence, again from West Africa, shows that MCSs are steered away from the saturated soils created by previous storms. This feedback makes predicting the track of a hazardous storm easier, though we do not know how strong the effect is in other regions of the world.This project will focus on how MCSs are affected by patterns of soil moisture and vegetation, through analysis of both satellite observations and CPMs. The work will discover how strong land effects are across the different hotspots of the world, and what processes are key to determining that strength. Experiments with a CPM will identify the surface patch sizes, ranging from 10s to many 100s km, which have the biggest impact on MCSs. Satellite data will be analysed to detect how MCS intensity and lifetime have been affected in regions with recent land use change (e.g. irrigation, deforestation, urbanisation). The work will explore how, as the world warms, and contrasts between wet and dry areas get stronger, the feedback between soil moisture patchiness and MCSs is changing. This matters because the feedback may amplify trends towards more extreme rain and longer gaps between storms. Identified observation-based relationships between the land and MCSs will also be used to scrutinise theoretical understanding and to evaluate the fast-emerging next generation of CPMs. This will include analysis of the world's first year-long global simulation from a land-atmosphere-ocean CPM able to capture the kilometre-scale motions within MCSs.Overall, the project will make substantial advances in understanding of how the land affects this powerful type of storm, with observations and model studies from across the world. The results will provide underpinning knowledge to improve prediction of storm hazards, informing decision making across weather to climate change time-scales.

中尺度对流系统（MCS）是世界上最强大的风暴之一，在许多地方是大风、闪电、山洪和龙卷风等灾害的主要原因。在整个热带地区，MCS占极端降雨日数的80%。它们是由雷暴形成的，形成一个数百公里宽的大型复合体，在陆地上传播数小时，有时甚至数天，沿途沿着特大暴雨。它们在某些“热点”地区特别普遍，包括阿根廷北方和印度、西非和中非以及美国大平原，温暖、潮湿的空气和有利的风共同支持它们的发展。在这些热点地区，迫切需要了解MCSs将如何随着世界变暖而变化，以便建造具有气候适应能力的房屋，道路，桥梁和水坝。传统的气候模式缺乏足够的空间分辨率来真实地模拟这些风暴。然而，在过去5年里，由于计算机能力的提高，高分辨率气候模型发生了革命。新的“对流许可模型”（CPM）可以代表MCS，并开始提供更好的预测，更好地了解MCS如何对其环境做出反应。我们知道，植被和土壤湿度的空间格局会影响空气温度、湿度和风流动，这些变化会影响强大MCS的发展位置（或是否发展）。例如，热带森林和沙漠之间的差异控制着各大洲的表面温度差异，通过有利的风力条件创造了MCS热点区域。由于全球变暖，这些地表温差已经在增加，并且在短短35年内，西非最强烈的MCS增加了两倍，导致那里的山洪暴发急剧增加。我们还知道，陆地表面会影响单个MCS轨迹。同样来自西非的证据表明，MCS被引导远离先前风暴造成的饱和土壤。这种反馈使预测危险风暴的路径变得更加容易，尽管我们不知道这种影响在世界其他地区有多强。本项目将通过分析卫星观测和CPM，重点研究MCS如何受到土壤水分和植被模式的影响。这项工作将发现世界上不同热点地区的土地效应有多强，以及什么过程是决定这种强度的关键。CPM的实验将确定的表面补丁大小，从10秒到许多100公里，这对MCS的影响最大。将对卫星数据进行分析，以查明在最近土地使用发生变化（如灌溉、毁林、城市化）的地区，MCS强度和寿命如何受到影响。这项工作将探索如何，随着世界变暖，潮湿和干燥地区之间的对比变得更强，土壤水分斑块和MCS之间的反馈正在发生变化。这很重要，因为反馈可能会放大更极端降雨和风暴间隔更长的趋势。确定的基于观测的土地和MCS之间的关系也将用于审查理论理解和评估快速出现的下一代CPM。这将包括分析世界上第一个为期一年的全球模拟，该模拟来自陆地-大气-海洋CPM，能够捕捉MCS内的超尺度运动。总体而言，该项目将通过来自世界各地的观测和模型研究，在了解陆地如何影响这种强大类型的风暴方面取得实质性进展。研究结果将提供基础知识，以改善风暴灾害的预测，为整个天气到气候变化时间尺度的决策提供信息。

项目成果

Untangling the importance of dynamic and thermodynamic drivers for wet and dry spells across the Tropical Andes

阐明热带安第斯山脉干湿期动态和热力学驱动因素的重要性

• DOI: 10.1088/1748-9326/acb72b
• 发表时间: 2023
• 期刊: Environmental Research Letters
• 影响因子: 6.7
• 作者: Klein C

Farmers' first rain: investigating dry season rainfall characteristics in the Peruvian Andes

农民的第一场雨：调查秘鲁安第斯山脉的旱季降雨特征

• DOI: 10.1088/2515-7620/ace516
• 发表时间: 2023
• 期刊: Environmental Research Communications
• 影响因子: 2.9
• 作者: Klein C

Classification of large-scale environments that drive the formation of mesoscale convective systems over southern West Africa

• DOI: 10.5194/wcd-4-773-2023
• 发表时间: 2023-09
• 期刊: Weather and Climate Dynamics
• 作者: F. Nkrumah;Cornelia Klein;K. A. Quagraine;Rebecca Berkoh-Oforiwaa;N. Klutse;Patrick Essien;G. M. Quenum;Hubert Azoda Koffi

The Representation of Soil Moisture-Atmosphere Feedbacks across the Tibetan Plateau in CMIP6

• DOI: 10.1007/s00376-023-2296-2
• 发表时间: 2023-08
• 期刊: Advances in Atmospheric Sciences
• 影响因子: 5.8
• 作者: J. Talib;O. Müller;E. J. Barton;C. Taylor;P. Vidale

Dry-to-Wet Soil Gradients Enhance Convection and Rainfall over Subtropical South America

干湿土壤梯度增强南美洲亚热带地区的对流和降雨

• DOI: 10.1175/jhm-d-23-0031.1
• 发表时间: 2023
• 期刊: Journal of Hydrometeorology
• 影响因子: 3.8
• 作者: Chug D