Urban microclimates have a great impact on the thermal comfort of city inhabitants, with the Urban Heat Island (UHI) and the Subsurface Urban Heat Island (SUHI) effects posing a growing challenge under the accelerating impacts of climate change. This thesis focuses on investigating the UHI and SUHI effects and exploring potential mitigation strategies within a controlled urban environment, specifically the ”Heat Square” at The Green Village in the Delft University of Technology. The Heat Square serves as an experimental urban environment designed to analyse various urban cooling measures. To capture the spatial and temporal variations in soil temperature within the Heat Square, Distributed Temperature Sensing (DTS) technology was deployed. DTS measures high-resolution temperature data, which allows for detailed analysis of the soil temperature response to different cooling scenarios, including the implementation of green infrastructure, shading, and reflective surfaces. These in-situ measurements were then compared with urban microclimate modeling results using ENVI-met, a Computational Fluid Dynamics (CFD) tool for modeling urban microclimatic conditions. ENVI-met, along with other urban microclimate models, can predict the impact of urban design on local temperature and thermal comfort indices. The findings of this research highlight the significant potential of green infrastructure and shading as effective strategies to mitigate the UHI effect. Specifically, the introduction of vegetation and shading elements resulted in noticeable reductions in both surface and air temperatures as well as Mean Radiant Temperature (Tmrt) within the urban environment. These findings were supported by performing simulations of different urban scenarios of the Heat Square. However, the study also highlighted challenges in accurately modeling urban microclimates, as shown by discrepancies between the DTS measurements and ENVI-met simulations. These differences suggest the need for further refinement of model parameters to better approximate the complexities of real-world urban environments. Overall, this thesis contributes to the broader understanding of urban cooling measures and their role in enhancing the resilience of cities to climate change. The insights gained from this research are intended to inform urban planning and design practices, promoting the development of more sustainable and climate-resilient urban spaces as well as the applicability of urban microclimate monitoring tools. Future research should focus on refining the ENVI-met model of the Heat Square to enhance its accuracy in properly simulation real-life responses of the urban environment to climatic variations. Additionally, exploring a broader range of urban cooling strategies, including water-based solutions and varying surface materials, could broaden knowledge on heat mitigation strategies. Studying soil thermal responses in other urban environments with DTS would also be valuable for studying indirect effects of the SUHI effect. Collaborations between researchers, urban planners, and policymakers are important to ensure that scientific findings are translated into practical applications that increase climate adaptability of urban environments.

Driven by global temperature increase and changing precipitation patterns, the intensifying hydrological cycle is expected to introduce more frequent and severe streamflow droughts. These changes will have a profound impact on agriculture, ecosystems and water management. This study analysed the spatial and temporal changes in streamflow droughts across 386 Mediterranean river basin from 1970 to 2019, focusing on their drought characteristics: duration, severity, intensity, maximum deficit, inter-arrival time, recovery rate and decline rate. The river basins were categorized into seven climatic regimes, and each was analysed for changes in these drought characteristics. Streamflow droughts were quantified
using the Threshold Level Method, defining drought events as periods in which daily streamflow is below a set threshold. To identify patterns, trends were assessed across four fixed time periods, along with multi-temporal analyses for both annual and seasonal changes. The analysis showed that annual streamflow droughts, although becoming longer, are getting slightly less severe and intense across the majority of river basins. However, distinct seasonal and regional variations were found. Between 1988 and 2019, winter and spring streamflow droughts experienced a decrease in duration and severity (up to -30% for winter) across the entire study area. On the other hand, regional differences were observed for summer and fall. During this same time period, summer and fall streamflow droughts in the Pyrenees, Southern France, Italy and Croatia have become much longer, more severe and more intense (20-40% for summer), whereas Central and Southern Spain experienced decreasing duration and drought deficit volumes. The implications of increasing streamflow drought conditions on the water availability in Mediterranean river basins is severe, which highlights the need for better understanding and water management of streamflow droughts.

Understanding wind profiles in urban areas is vital for various applications including urban planning and environmental science. This study aims to characterise the modification of wind profiles in The Heat Square through anemometer observations, focusing on the influence of building morphology. Previous studies have endorsed methodologies that consider building height variability. Still, our results suggest that rule-of-thumb morphometric methods based on average building height offer closer anemometric estimates in this specific urban setting. Unfortunately, the lack of inertial sublayer (ISL) wind speed measurements constrains the generalizability of our findings. Additionally, sub-optimal anemometer installation height poses another limitation to the study. Despite these constraints, the results should serve as reasonable estimates for modelling efforts concerning heat flux and heat stress. The study strongly recommends further research to address existing limitations, aiming to generate more reliable field estimates, particularly for The Heat Square and The Green Village.