Meso-Scale Spatiotemporal Analysis of Future Drought Characteristics in Northern Thailand Under Climate Change and Variability

Abstract This study examines the spatio-temporal characteristics of drought under climate change and variability in northern Thailand, located within the Southeast Asian monsoon region, using the 3-month standardized precipitation evapotranspiration index (SPEI-3). The analysis is conducted utilizing a high-resolution gridded dataset derived from the statistical downscaling of an optimally selected ensemble of five global climate models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6), under the SSP2-4.5 and SSP5-8.5 scenarios. The study spans the historical period (1981–2014) and three future periods: near future (2026–2050), mid-future (2051–2075), and far future (2076–2100). The results indicate increasing trends in precipitation, mean temperature, and potential evapotranspiration across both scenarios, with more pronounced changes under SSP5-8.5. The SPEI-3 index reveals a decreasing trend in drought severity throughout the 21st century, with the most significant reductions projected for the far future under SSP5-8.5. Spatial analysis found distinctly decrease drought for the far future in Southwest and West of Northern Thailand under SSP2-4.5 and SSP5-8.5, respectively. However, yearly variations are different in different areas. In the far future under SSP2-4.5, yearly variations increase in the Northeast but decrease in the Southeast. Under SSP5-8.5, yearly variations increase in the central region but decrease in the Northern and Southeast areas. Spatial variability analysis using spatial SD shows a decrease in the near future but an increase in the far future. Meanwhile, future drought frequency and duration are expected to decline relative to the historical baseline, though certain areas may experience localized increases. Drought peaks demonstrate scenario-dependent variations. Under SSP2-4.5, the highest drought severity is projected in the far future for upper northern Thailand, whereas SSP5-8.5 indicates peak severity in the near future for lower northern Thailand. Significant spatial differences in drought characteristics were observed, underscoring the importance of accounting for local mesoscale climatic effects and climate variability in drought studies. These findings offer critical insights into future drought conditions in northern Thailand, emphasizing the need for policymakers to develop and implement targeted adaptation measures to address climate change's impacts effectively.