Public defence in Water and Environmental Engineering, MSc. (Tech.) Ville Lindgren

Title of the thesis: Spatial precipitation information in hydrology: Addressing hydroclimate variability and generating spatially distributed design storm ensembles

Thesis defender: Ville Lindgren
Opponents: Assistant Professor Athanasios Paschalis, University of Cyprus, Cyprus; and Assistant Professor Pekka Rossi, University of Oulu, Finland
Custos: Professor Harri Koivusalo,Aalto University School of Engineering, Department of Built Environment

Adaptive models that incorporate hydroclimate variability can enhance climate adaptation and support resilient built environments.

Water is essential for life, and precipitation brings water from the atmosphere to the ground in various forms, such as rain, hail, and snow. Precipitation plays a critical role in the water cycle and is of great interest in hydrology and meteorology. While previous studies have extensively covered average hydroclimatic conditions in Finland, less attention has been given to understanding variability around these averages. Traditional rain gauges provide accurate local rainfall measurements but lack the spatial information, which is crucial for understanding an area's hydrological response to precipitation. Weather radars address this gap by providing detailed spatiotemporal data, which can enhance hydrological assessments and improve our understanding of rainfall dynamics.

This doctoral thesis investigates historical changes in hydroclimate variability in Finland and evaluates the benefits of radar-based rainfall information via rainfall simulations and hydrological assessments. This research contributes to enhance understanding about design storms, uncertainties in rainfall-runoff modelling, and spatiotemporal rainfall variability. Enhanced knowledge of rainfall patterns supports water resource management and flood risk mitigation, thereby advancing sustainable societal development and increasing resilience against shifts in climate variability and extreme events, like floods and droughts.

The thesis identifies spatial and temporal shifts in hydroclimate variability in Finland, revealing areas with consistent patterns of change. Comparing these results with previous studies shows that trends in average hydroclimate conditions do not always align with changes in variability. The thesis also introduces a rainfall simulation model and a novel approach to quantify variability and uncertainty of rainfall events. This approach facilitates more thorough assessments of the hydrological impacts of spatiotemporal rainfall characteristics. The approach demonstrates the advantages of spatial rainfall information, showing how temporally similar rain events can result in drastically different accumulations at local scales due to varying spatial patterns. Additionally, the alignment and speed of advancing rain event can significantly affect event duration and accumulations.

Evaluating hydroclimate variability alongside average conditions provides a comprehensive view of extreme events. Understanding past and present hydroclimatic conditions enables better predictions of future scenarios, which are essential for planning and decision-making processes. Further development of realistic and adaptive models can assist in simulating current and future hydroclimatic conditions, supporting informed decision-making and fostering resilient infrastructure and sustainable societies.

Keywords: hydroclimate variability; precipitation; rainfall; weather radar; pySTEPS; rainfall simulation; design storm; ensemble simulation; SWMM

Thesis available for public display 7 days prior to the defence at Aaltodoc. 

Contact information: www.linkedin.com/in/ville-valtteri-lindgren; ville.va.lindgren@gmail.com; ville.v.lindgren@aalto.fi