Drought Characterization and Propagation Under Changing Climate

Abstract

As recurrent and severe climate events, droughts pose significant threats to water resources, food security, and ecosystems. This thesis aims to comprehensively analyze drought events, focusing on their characterization and propagation under changing climate conditions. The research employs the Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized Soil Moisture Index (SSMI) as key indicators for quantifying drought severity and soil moisture conditions. Both stationary and non-stationary parameters are calculated, encompassing various approaches such as trend analysis using moving block bootstrap and time-sliding window methods. This enables the identification of patterns and trends in drought events, contributing to a better understanding of their temporal dynamics. To enhance the characterization of droughts, the study incorporates the application of run theory, enabling the determination of drought periods, development periods, recovery periods, and instantaneous speed. This detailed analysis provides valuable insights into the duration and intensity of drought events, facilitating more effective drought management strategies. Moreover, the thesis explores the propagation of drought events by analyzing the lag between SPEI and SSMI drought events. This investigation sheds light on the transition of meteorological drought to agricultural drought and helps in identifying the factors influencing drought propagation. Advanced software tools including MATLAB and R Studio are utilized for data analysis, enabling accurate calculations of parameters and the development of stationary and non-stationary standardized indices. The study incorporates data from diverse sources, ensuring a comprehensive analysis that captures the complexity of drought events under changing climate conditions. The analysis revealed interesting trends in the location parameter and scale parameter values for both meteorological and agricultural drought. Positive and negative trends were observed in different months, indicating variations in drought severity and variability throughout the year. Additionally, the non-stationary approaches, such as the non-stationary Standardized Precipitation Evapotranspiration Index (NSPEI) and non-stationary SSMI (NSSMI), demonstrated improved performance in capturing drought conditions by considering the non-stationarity of the data. The examination of event duration, development period, recovery period, severity, development speed, and recovery speed provided valuable information on the temporal characteristics of drought events. While there were variations across different regions, the average values generally indicated relatively short durations, moderate propagation rates, and slower recovery processes for drought events. The findings of this research contribute to the advancement of knowledge in water resources planning and management. The comprehensive understanding of drought characterization and propagation obtained through this study can assist policymakers, water resource managers, and stakeholders in making informed decisions to mitigate the adverse impacts of droughts. Furthermore, the research outcomes will aid in the development of sustainable practices to address the challenges posed by droughts in a changing climate.