Exploring Climate Variability and Soil Moisture Dynamics to Refine Drought Quantification in East Asia Monsoon Regions

Drought extremes in hydrological systems are closely tied to soil moisture dynamics. However, the influence of climate variability on soil moisture, particularly in the East Asia monsoon region, remains insufficiently explored. This study examines soil moisture in Taiwan, combined with satellite data, to investigate the impacts of summer monsoons. For instance, the positive phase of the Pacific-Japan Pattern has been identified as a key driver of interannual extremes in compound heat and drought events. These phenomena are exacerbated by soil moisture deficiencies, which intensify dry conditions, elevate air temperatures, and result in significant societal and agricultural damage. This research focuses on the linkage between drought characteristics and climate variability from a soil moisture perspective, in contrast to traditional indices in Taiwan that predominantly rely on rainfall data. Advanced analytical approaches, such as AutoEncoder (AE) and Principal Component Analysis (PCA), were utilized to enhance drought quantification by integrating satellite observations with high-resolution downscaled datasets. PCA results emphasize the critical role of interannual internal modes, like the Pacific-Japan Pattern, in driving drought conditions. However, discrepancies observed between AE and PCA outcomes highlight the need for further investigation into nonlinear relationships underlying drought dynamics.