Spatial Heterogeneity of Surface Soil Grain Size in Central Asia and Its Response to Seasonal Atmospheric Circulation Dynamics

Surface soil grain-size distribution (GSD) is a fundamental terminal record of aeolian processes and land-surface erodibility. However, a macro-scale understanding of GSD spatial heterogeneity and its quantitative coupling with seasonal atmospheric circulation dynamics in Central Asia remains insufficient. Based on an extensive dataset of 325 surface soil samples across Kazakhstan, Uzbekistan, Kyrgyzstan, and Tajikistan, this study systematically investigates the GSD patterns and their climatic drivers. Our results reveal a pronounced spatial gradient: coarse-textured soils dominate the northwestern and eastern desert plains, whereas fine-grained sediments are sequestered in the southeastern mountain-basin systems. We demonstrate that this heterogeneity is rigorously governed by seasonal wind regimes: the Siberian High directs coarse particle entrainment and transport during spring, while the mid-latitude westerlies and local topographic modulation (e.g., the Tian Shan and Pamir barriers) control the fine-grained sorting continuum. Furthermore, the desiccated Aral Sea bed serves as a distinctive anthropogenic dust source, perturbing regional natural sorting patterns. These findings provide critical empirical constraints for dust emission modeling and underscore the sensitivity of Central Asian land surfaces to shifting atmospheric circulation patterns.