Future droughts in Great Britain: from weather to Wensum

Reyniers, Nele (2023) Future droughts in Great Britain: from weather to Wensum. Doctoral thesis, University of East Anglia.

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Abstract

Droughts can cause enormous damages and are changing under anthropogenic climate change. In this thesis, climate and hydrological models were used to investigate projected future droughts in Great Britain, emphasising the contributions of methodological and modelling choices to the resulting projections and their uncertainty. First, non-negligible biases were found in the regional climate model projections of UKCP18, the latest set of regional climate projections for the UK (UKCP18-RCM), and therefore, two bias adjustment methods were applied successfully. The ensemble projects wetter, warmer winters and hotter, drier summers, but with more complex changes for different temperature and precipitation indices, including different changes in the extreme ends of their ranges. These changes are well-preserved after bias-adjustment, but the change factor approach failed to capture changes in some precipitation metrics. From these data, projected changes in drought characteristics were derived using two contrasting drought indicators, the Standardised Precipitation Index (SPI) and the Standardised Precipitation Evapotranspiration Index (SPEI). Projected increases in drought frequency and extent, and the dominant contribution of future summer droughts to annual-scale deficits, are far greater based on the SPEI than based on the SPI, highlighting the important role of increased evaporative demand for future droughts. The largest changes were found for extreme droughts. Finally, an ensemble of hydroclimatic impact model chains was calibrated for the Wensum catchment. Detailed evaluation using multiple criteria strongly reduced the uncertainty in the streamflow drought frequency projections, especially the contribution from hydrological modelling choices. Increasing streamflow drought frequency was projected for the Wensum, with greater increases for more severe droughts and higher levels of global warming. This resulted from both a lengthening of individual drought events (especially for moderate droughts) and an increase in the number of events (primarily for more severe droughts). This work concludes with recommendations for future hydrological climate change impact studies.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Depositing User:	Nicola Veasy
Date Deposited:	15 Apr 2024 10:11
Last Modified:	15 Apr 2024 10:11
URI:	https://ueaeprints.uea.ac.uk/id/eprint/94906
DOI:

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