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Μελέτη επιπτώσεων κλιματικής μεταβολής σε βασικές υδρολογικές παραμέτρους και ο ρόλος του μεροληπτικού σφάλματος

Gryllakis Emmanouil

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Summary

The study of the potential impacts of climate change in water resources aims to provide the required information needed for human adaptation. Adaptation measures aim to reduce the human and physical systems vulnerability to changes in climate. The basic tool for the climate research is the climate models. Climate models can simulate the past climate, while when they are forced with appropriate future emission scenarios they can provide a projection of the future climate. However climate projections cannot be used to impact studies in their native form, due to the systematic errors that they exhibit. Thus, it is a necessary process to correct those biases in order to make the climate model data appropriate for impact models that are calibrated against observations. In the presented dissertation, a new methodology of statistical bias adjustment of precipitation data was developed. The methodology was tested for its performance in the results of a GCM, while the results of the methodology were compared against another widely used, state of the art methodology. It was found that the developed methodology improved the precipitation bias correction in the mean but also in the upper percentiles, comparing to the other method.Moreover, the broader used, state of the art climate experiments CMIP3 and CMIP5, NARCCAP, EURO CORDEX 44, EURO CORDEX 11 and North America CORDEX, were assessed for their ability to represent the precipitation and temperature regime over Europe and North America. A comprehensive assessment of the different regional and global climate experiments using multiple performance indicators revealed the most skillful experiment to simulate the past climate, for each study area.The climate information was used to assess the effect of the projected climate change over four selected watersheds with and without adjusting the bias in precipitation and temperature. The comparison shown that the bias correction increased the performance of the hydrological simulations against the observed flow data, while it reduced the uncertainty among the different climate simulations. Then a trend analysis was performed in order to examine the degree that each bias adjustment methodology could affect the long term – annual trend in the precipitation and temperature. It was found that the developed precipitation bias adjustment methodology could affect in a limited degree the trend of change in the precipitation. The trend change in temperature was also small. Nonetheless, the combined change of the aforementioned variables, may affect the trend in the flow in a larger degree.Then, the change in seasonality was examined for the best-performing climate experiments for each case study area. Finally the change in extreme precipitation events was examined for its influence in extreme runoff events under the change in climate.

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