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Technical University of Crete (TUC) 2010

Extreme hydrometeorological phenomena and the impact of climatic change : application in the region of Crete, Greece

Koutroulis, Aristeidis of Georgios

Titre : Extreme hydrometeorological phenomena and the impact of climatic change : application in the region of Crete, Greece

Ακραία υδρομετεωρολογικά φαινόμενα και επίδραση της κλιματικής μεταβολής στην εξέλιξή τους : εφαρμογή στην περιοχή της Κρήτης

Auteur : Koutroulis, Aristeidis of Georgios

Etablissement de soutenance : Technical University of Crete (TUC)

Grade : Doçtor of Philosophy (PhD) 2010

Résumé
Climate change is expected to have a significant impact on the hydrologic cycle, creating changes in flood and drought occurrence. The Mediterranean has been described as one of the main climate change “hot-spots”, with recent simulations showing a collective picture of substantial drying and warming. Analysis of climate models data indicates that today’s extreme events will intensify, i.e., precipitation on average is likely to be less frequent but more intense and droughts are likely to become more frequent and severe in some regions. The present Doctoral thesis aims in the study of extreme hydrometeorological phenomena in the region of Crete. At a first step, floods and drought events were analyzed focusing in the peculiar Mediterranean environment, describing relative climatic tendencies. The state-of-the-art Ensembles dataset was employed to assess the impact of the changing climate on basic hydrometeorological parameters for the island of Crete at basin scale. Data analysis for the period 1970-2100 reveals an overall decreasing precipitation trend which, combined with a temperature rise, leads to substantial reduction of water availability. Secondly, the seasonality of the hydrometeorologic characteristics of floods that occurred in Crete during the period 1990-2007 is presented. Hydrological characteristics were analyzed using seasonality indices. Moving to finer spatial scales, a holistic approach for estimating flash flood peak discharge, hydrograph, and volume in poorly gauged basins, where the hydrological characteristics of the flood are partially known, due to stage gauge failure, is applied for the analysis of the 13th January 1994 flash flood event at Giofiros river basin, Crete. At a next step, a new modified drought index, named SN-SPI (Spatially Normalized-Standardized Precipitation Index), has been developed for assessing meteorological droughts. The SN-SPI is a variant index to SPI (Standardized Precipitation Index) and is based on the probability of precipitation at different time scales, but it is spatially normalized for improved assessment of drought severity. Results of this index incorporate the spatial distribution of precipitation and produces improved drought warnings. This index is applied in the island of Crete. A 30-year long average monthly precipitation dataset from 130 watersheds of the island is used by the above indices for drought classification in terms of its duration and intensity. The ability of ensemble Regional Climate Models to reproduce basic hydrometeorological variables for local impact studies is examined. Optimum weighting and bias correction methods are applied for the extraction of hydrologic time series used in impact studies for floods and droughts. Study results improve the current knowledge regarding the mechanisms of extreme hydrometeorological events and promote observation and forecasting strategies.

Mots clés : Climate changes ; Extreme events ; Hydrometeorology ; Floods ; Droughts ; Crete

Présentation

Page publiée le 15 novembre 2022