Tracking Storms and Extreme Rainfall over Brazil in Convection-Permitting Simulations of Present and Future Climate (Ref: 4256)

巴西非常容易受到自然灾害的影响，其中70%是水文气象性质的灾害，如洪水和干旱(Alves等人，2020年)。该区域的极端降水经常与有组织的风暴系统有关，例如中尺度对流系统(Silva和Berberg，2006年)。巴西上空未来风暴和降水的变化可能会产生重大影响，但高度不确定，部分原因是当前一代的全球气候模式(CMIP6模式)运行在水平网格分辨率上，太粗糙，不能明确表示对流风暴。最近在南美洲完成了新的千米级、允许对流的分辨率的前沿气候模拟。巴西各地的降雨系统是在多个尺度上组织起来的，从局部中尺度对流到整个大陆的热带-温带云带。允许对流的模拟可能比更粗分辨率的模拟更真实地代表巴西气候的许多要素，特别是这些对流系统。这可能是更可靠地诊断未来对流风暴极端变化的关键。项目目标和方法本项目将评估风暴及其相关降水在最先进的对流允许模式(CPM)气候模拟中的表现。这将包括与现代观测的比较，对气候变化的反应的分析，以及与对现代气候和对气候变化的反应的较粗分辨率模拟的比较。特别关注人口稠密的巴西南大西洋辐合带(SACZ)地区，在那里，大规模的热带-温带相互作用是产生有组织的系统和降水的关键(Ambrizzi和Ferraz，2015)。本项目将使用多种风暴跟踪方法来捕捉从对流尺度到中纬度风暴尺度的系统在巴西上空的轨迹。本项目将重点回答以下研究问题，但也将在整个学习过程中受到学生自己想法的强烈影响：1)巴西上空的风暴在目前的CPM运行中表现如何？这将包括分析有组织系统的启动、传播、规模和其他特征，以及它们与降水和降水极值的关系2)巴西上空的风暴如何应对CPM运行中的气候变化？本课程将研究有组织系统的变化及其与降水的关系。我们还将探索这些变化的驱动因素，例如湿度和大范围环流的变化。3)模式分辨率如何影响当今和未来气候中巴西上空的风暴？CPM的结果将与CMIP6模拟和/或含参数对流的区域气候模拟的风暴跟踪和降水分析进行比较。

Brazil is highly vulnerable to natural disasters, 70% of which are hydro-meteorological in nature, such as floods and droughts (Alves et al., 2020). Extreme precipitation in the region is frequently associated with organised storm systems such as mesoscale convective systems (Silva and Berbery, 2006). Future changes in storms and precipitation over Brazil are likely to have large impacts but are highly uncertain, partly because the current generation of global climate models (CMIP6 models) run at horizontal grid resolutions that are too coarse to explicitly represent convective storms.New cutting-edge climate simulations at kilometre-scale, convection-permitting resolution have recently been completed over South America. Rainfall systems across Brazil are organised at multiple scales from local mesoscale convection through to continent-wide tropical-extratropical cloud bands. The convective-permitting simulations are likely to represent many elements of Brazilian climate more realistically than coarser resolution simulations, especially these convective systems. This may be key to more robust diagnosis of future changes in convective storm extremes.Project Aims and MethodsThis project will assess the representation of storms and their associated precipitation in state-of-the-art convection-permitting model (CPM) climate simulations. This will include a comparison with present-day observations, analysis of the response to climate change, and a comparison with coarser resolution simulations of both the representation of present-day climate and the response to climate change.A particular focus will be the heavily populated South Atlantic Convergence Zone (SACZ) region of Brazil, where large-scale tropical-extratropical interactions are key to producing organised systems and precipitation (Ambrizzi and Ferraz, 2015). Multiple storm-tracking approaches will be used to capture systems from the convective scale through to the mid-latitude storm scale as they track over Brazil.This project will focus on answering the following research questions, but will also be strongly influenced by the student's own ideas over the course of the studentship:1) How well are storms over Brazil represented in the present-day CPM runs? This will include analysis of the initiation, propagation, size and other characteristics of organised systems, together with their relationship to precipitation and precipitation extremes.2) How do storms over Brazil respond to climate change in the CPM runs? Changes to organised systems and their relationship to precipitation will be examined. We will also explore the drivers of these changes, e.g. changes in moisture and large-scale circulation.3) How does model resolution affect storms over Brazil in present-day and future climates? CPM results will be compared with a storm tracking and precipitation analysis of CMIP6 simulations and/or regional climate simulations with parametrised convection.