CFI Workshop on Urban Rainfall in a Warming World

Abstract

This presentation is in two parts. First, we answer the question, what evidence do we have for changes in sub-daily rainfall for Australia? Following this, we pose the question, how do we incorporate these changes in design flood estimation?

Strong changes in sub-hourly rainfall are detected in observed extreme rainfall across Australia. But for longer durations there is little to no change signal in the observed rainfall, albeit a change signal detected in regional climate model projection. Increases are shown to be greater for rarer extremes, with less of a change signal detected for more frequent events. The range of results suggests that no one line of evidence is likely to provide all the information necessary for decision making under climate change, particularly for the rarest extremes, which show the greatest increase. Building on this research, Australia has implemented a new set of engineering guidelines that practitioners will use across the continent whereby both extreme rainfalls and antecedent conditions are factored for climate change. While this presentation is focused on the Australian experience, evidence is presented that will be applicable for the diverse changes in extreme rainfall across the globe.

Presenter:

Dr. Conrad Wasko

University of Sydney, Australia

Speaker Profile

Dr Conrad Wasko is a Sydney Horizon Fellow at the University of Sydney. His research focuses on understanding the effects of climate change on extreme rainfall and flooding. He has published over 70 papers in international peer reviewed journals and is cited by the Intergovernmental Panel on Climate Change. His work on updating Australia’s guidelines on flood estimation for climate change earned him the Batterham Medal from the Australian Academy of Technological Sciences and Engineering.

Abstract:

To properly manage urban flood risk, we need to estimate very rare but still possible rainfall events on sub-daily or even sub-hourly temporal scales. For example, we need to estimate magnitudes that are expected to occur on average every 100 or 200 years only based on a few decades of observations. The problem is typically approached by using statistical tools from extreme value theory, completely neglecting the physics behind precipitation. I will showcase some fundamental flaws in these traditional approaches and layout the theory to derive new statistical models of extreme precipitation that are based on physics. I will present applications of these new models in diverse climatic settings and describe some possible ways to include physical covariates in the description of the extremes of interest. This is a natural way for including the impacts of climate change directly in the formulation of our models.

Presenter:

Dr. Francesco Marra

University of Padova, Italy

Speaker Profile

Francesco Marra graduated in Physics at the University of Bologna and got a PhD in Hydrology at the University of Padova. He was a Lady David Postdoctoral Fellow at the Hebrew University of Jerusalem and permanent researcher at the National Research Council of Italy. He is now Assistant Professor of atmospheric physics at the University of Padova. His main research interests include precipitation physics, climatology and statistical hydrology, with a special focus on extreme precipitation and its impacts.

Abstract:

Singapore, a rapidly urbanising tropical city-state, faces increasing flood risks due to impervious surfaces, cloudbursts, and climate change. This study analyzes the spatiotemporal patterns of urban flooding in Singapore, identifying 108 transient flood events—all associated with short-duration, high-intensity cloudbursts. We propose the term burst flooding to describe urban floods driven by such extreme precipitation events. Our analysis reveals a clustering of cloudbursts during November–December in La Niña years, underscoring the influence of large-scale climate variability on local flood hazards. To enable real-time monitoring, we developed an AI-based detection system fusing traffic camera feeds and social media imagery. This hybrid approach achieves 92% precision in flood localization, leveraging existing urban infrastructure for scalable, low-cost sensing. By integrating computer vision with crowd-sourced data, the framework bridges gaps in traditional sensor networks, offering cities a tool for adaptive flood management amid climate extremes.

Presenter:

Dr. Jingyu Wang

Nanyang Technological University

Speaker Profile

Dr. Wang Jingyu is an assistant professor in the Humanities & Social Studies Education Academic Department, NTU. Before joining NTU, he worked as a postdoctoral associate at the Department of Atmospheric Sciences & Global Change, Pacific Northwest National Laboratory, observing and simulating mesoscale convective systems and the related natural hazards of tornado and hail. Jingyu received his Ph.D. degree in Atmospheric Sciences (with a minor degree in Hydrology) from the University of Arizona, with the focus of in-situ observation of cloud microphysics using research aircraft.

Abstract:

Urbanization in coastal areas is a global phenomenon. These coastal cities continue to grow and attract infrastructure investments but also suffer from flooding-related vulnerabilities. Cities face a dual flood risk: growing threats from severe thunderstorms and internal vulnerabilities from sprawl and impervious landscapes that exacerbate runoff and drainage challenges. This talk will discuss the current understanding of urban thunderstorms, and how urban heat, city size, and even shape can affect flood risks for cities. Building on this scientific understanding, the opportunities now available through integration of AI/ML techniques and satellite datasets through City Digital Twin frameworks to develop engineering solutions will also be discussed. A successful collaboration between academia, city municipal operations, and community partners to build an integrative partnership through City CoLabs will be discussed.

Presenter:

Professor Dev Niyogi

The University of Texas at Austin, USA

Speaker Profile

Dr. Dev Niyogi is William Stamps Farish Chair Professor at the Department of Earth, and Planetary Sciences in the Jackson School of Geosciences at the University of Texas at Austin. He is also an affiliated faculty in the Civil Architectural and Environmental Engineering, the Oden Institute of Computational Science and Engineering, as well as the LBJ School of Public Affairs. Professor Niyogi also holds a UNESCO Chair in Open Sustainable Innovative Solutions focusing on AI, Water, and Cities.  He also is an Emeritus Professor at Purdue University, former State Climatologist, and has been a visiting Professor and researcher with global research and academic mentoring. He is Editor and associated editor of various journals, published over 300 peer reviewed journal papers, that have been cited over 30,000 times. The India Meteorological Society recognized him recently with a Fellowship and the American Meteorological Society awarded him the Landsberg Award for “ decades of leadership and pathbreaking discoveries related to assessing urban climate extremes, their prediction, and mitigation using data - model integration, and local to global partnerships”. He is currently working on using data - driven approaches to translate the scientific work undertaken into decision tools and portals with a particular focus on sustainable cities.

Abstract:

In light of rapid urban growth and global climate change, understanding how these factors interact to affect extreme rainfall is crucial for the resilience of cities. This presentation explores the impacts of climate change and urbanization on extreme rainfall patterns, drawing on high-resolution data and modeling from two major Asian cities: Shanghai and Singapore. The results reveal that urbanization can significantly enhance convective rainfall, driven by urban-surroundings hydrothermal differences and diurnal cycles, while climate-induced sea surface temperature warming plays a dominant role in shaping the structure and intensity of typhoons. In rapidly urbanizing tropical cities, extreme rainfall events are characterized by smaller spatiotemporal scales and rapid attenuation. Moreover, their total rainfall amount, spatial extent, and temporal persistence have increased in response to changing environmental conditions. This work highlights a clear intensification of urban extreme rainfall and underscores the urgent need for adaptive planning to mitigate future climate risks.

Presenter:

Dr. Qi Zhuang

National University of Singapore

Speaker Profile

Dr. Qi Zhuang is a Research Fellow in the Department of Civil and Environmental Engineering (CEE) at the National University of Singapore. She received her Ph.D. in Civil Engineering from Tongji University, China, in 2025, which included two years as a visiting scholar at the University of Lausanne, supported by the China Scholarship Council (CSC). Her research focuses on urban hydrometeorology, with particular interest in the interactions among climate change, urbanization, and extreme rainfall variability.

Abstract:

Designing urban drainage systems that can cope with future extreme rainfall requires understanding how urbanization and climate change interact to influence storm intensity and flood risk. Using weather radar observations and numerical simulations, we quantified how city size affects extreme rainfall properties, revealing a clear, non-linear relationship between urban growth and rainfall intensification driven primarily by urban heat island effects, across diverse cities and climates. We then examined the compound influence of urbanization and climate change, showing that their combined effect can markedly exceed impacts estimated from climate change alone. Building on these insights, we developed new modeling strategies to generate synthetic extreme storms for future city and climate scenarios, explicitly incorporating projected intensification. Coupled with hydrodynamic models, these storms enable robust assessments of future urban flood hazards, providing actionable knowledge to support the design of flood-resilient cities.

Presenter:

Dr Nadav Peleg

University of Lausanne

Switzerland

Speaker Profile

Since 2021, Assistant Prof. Nadav Peleg has led the Hydrometeorology and Surface Processes group at the University of Lausanne. His research investigates hydrometeorological processes across spatial and temporal scales, with a focus on how climate change and urbanization alter extreme rainfall and flooding at both catchment and urban scales. Working in Switzerland and internationally, he develops and applies stochastic and physically based models to advance understanding of these dynamics and support climate-resilient water management and urban planning.

Round-Table Discussion – Storm Design in a Changing Climate

Panellist:

• Dev Niyogi
• Conrad Wasko
• Francesco Marra
• Dr Nadav Peleg

Moderator: Prof. Vladan Babovic (NUS)