Abstract
This thesis investigates extreme events, focusing on heatwaves, droughts, and their interactions with terrestrial water storage (TWS), land use land cover (LULC), and large-scale atmospheric processes. Utilizing advanced multivariate bias-corrected climate models, we analyze the spatiotemporal variability of Heatwave characteristics, revealing an intensification of heatwave attributes and earlier onsets across multiple regions. Notably, precipitation modulates heatwave frequency by 57% in Western South Africa, while the Tropical Northern Atlantic index influences global heatwave frequency by 80% in Northern South America. The interaction between hydrometeorological extremes and atmospheric dynamics highlights regional fingerprints such as the critical role of monsoon winds and vertically integrated vapor transport in modulating heatwave frequency and intensity.Furthermore, human thermal stress from heatwaves, quantified using the Universal Thermal Climate Index (UTCI), is analyzed across different LULC categories, revealing significant regional disparities. For instance, primary forests in the Southern Hemisphere exhibit a strong negative correlation with UTCI values, reducing daytime surface temperatures and mitigating thermal stress. Conversely, urbanization and cropland expansion are associated with increased thermal stress, particularly in tropical regions. We project future thermal stress trends under Shared Socioeconomic Pathways (SSPs), showing a pronounced increase in heat stress exposure, with rural populations in regions like East Africa and South Asia experiencing up to 20 million person-days of heatwave exposure under SSP 245 and over 60 million person-days under SSP 585. Urban areas, however, face unique challenges due to the urban heat island effect, which exacerbates heatwave severity and duration.
We also examine the cascading impacts of heatwaves on water resources and human thermal stress, demonstrating that high TWS does not always mitigate heatwave severity due to localized accessibility constraints and timing mismatches. These findings underscore the feedback mechanisms between moisture availability, temperature anomalies, and heatwave propagation. Additionally, vegetation health indices (VHIs), including the Vegetation Condition Index (VCI) and Temperature Condition Index (TCI), reveal that low VCI and TCI values correlate strongly with unfavorable moisture and thermal conditions, contributing to drought development and vegetation stress. Collectively, these findings advance the understanding of extreme climate events' multiscale interactions and provide a robust framework for developing targeted mitigation and adaptation policies aligned with the objectives of the United Nations Sustainable Development Goals, particularly SDG13.
| Date of Award | 23 Apr 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Xuan WANG (Supervisor), Wen ZHOU (External Co-Supervisor) & Mei Yee Kenneth LEUNG (Co-supervisor) |
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