Spring Snowmelt Flood Disasters in Altay, Northwest China: Spatio-Temporal Distribution and Mechanisms

Study region : the Altay region in Northwest ChinaStudy focus : The occurrence frequency, intensity and impacts of spring snowmelt flood disasters have changed remarkably. Nonetheless, the understanding of snowmelt floods and their causes remains inadequate in Altay. In this study, we focus on the essential characteristics of 49 spring snowmelt flood disasters and investigate the associated atmospheric circulation anomalies and local thermal conditions of temperature extreme raised processes triggered warming-type flood events.New hydrological insights for the region : The spring warming-type snowmelt flood is dominated in Altay during 1984–2018. The floods associated with a deep high-pressure system over northern Central Asia that intensified and shifted northward, and affecting positive geopotential height anomalies. In addition, the anomalous southeasterly winds at 850 hPa were also notable factors. The zonal air temperature exhibited positive anomalies, and that extended to the upper troposphere. Also, the 0℃ layer height rose. The thermal condition exhibits different characteristics in the spring months, the upward energy flux from the surface was enhanced, favoring local warming in both March and April. In the May flood, the total cloud cover decreased which increased the net shortwave radiation flux reaching the surface and thus lead the temperature increase anomalous. These results provide valuable insights for prediction flood risk by depend on the related physical background of snowmelt floods in Altay.