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

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 Methods
This 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.