Spring snowmelt flood disasters in Altay, Northwest China: Spatio-temporal distribution and mechanisms

Study region: Altay region in Northwest China. Study focus: The frequency, intensity, and impacts of spring snowmelt flood disasters have changed significantly. However, there is still a limited understanding of snowmelt floods and their causes in Altay. In this study, we focus on the essential characteristics of 49 spring snowmelt flood disasters and explore the related atmospheric circulation anomalies and local thermal conditions that contributed to extreme temperature rises, triggering warming-type flood events. New hydrological insights for the region: From 1984-2018, spring warming-type snowmelt floods predominated in Altay. These floods were associated with a deep high-pressure system over northern Central Asia, which intensified and shifted northward leaing to positive geopotential height anomalies. Additionally, southeasterly anomalies at 850 hPa significantly influenced these events. Zonal cross-sections of average air temperature and vertical circulation anomalies exhibit positive and descending motion anomalies, with the 0 degrees C layer height rises. The thermal conditions in spring show distinct characteristics, including enhanced upward energy flux from the surface, which favors to local warming in both March and April. In May, downward motion due to reduced cloud cover, resulting in an increase in net shortwave radiation flux reaching the surface. These results provide valuable insights for further exploration of the precursor signals associated with snowmelt floods in the Altay.