Snow Cover Inversion Driven by Dzud Events in Mongolia from 2000 to 2024

Amid global climate change and extreme weather conditions, sudden dzud events in arid grassland regions inflict severe disasters on herders, livestock, transportation, and the economy. In particular, Mongolia experiences frequent dzud events in recent years, bringing devastating consequences. However, studies on the spatiotemporal distribution characteristics of snow cover during dzud events in Mongolia remain relatively scarce and fail to adequately explain the anomalous features and impacts of extreme snowfall. Therefore, this study examined the spatiotemporal distribution characteristics of snow in the five most severe dzud events in Mongolia from 2000 to 2024. We utilized the Normalized Difference Snow Index (NDSI) extraction method based on 500 m resolution MODIS10A1 data, with the results validated against 10 m resolution Sentinel-2 imagery. The study produces several interesting results: (1) Snow cover in Mongolia generally increases from south to north with rising terrain elevation. Although its interannual variation is highly unstable, a slight decreasing trend is observed over the past 25 years. (2) Significant regional differences form a fan-shaped snow distribution pattern centered around 45–52° N, with trend analysis indicating intensification in the west and weakening in the east, except for extreme weather events. (3) During dzud events, the snow cover fraction (SCF) generally exceeds the multi-year average, exhibiting a pronounced and abrupt rise, while snow cover and livestock mortality fluctuate in synchrony. By revealing the spatiotemporal distribution patterns of snow during dzud years in Mongolia, this research provides an evidence-based reference for the understanding of extreme winter climatic events and disaster risk reduction in arid grassland regions.