Spatiotemporal Variation of Snow Cover Frequency in the Qilian Mountains (Northwestern China) during 2000–2020 and Associated Circulation Mechanisms

Linking snow cover frequency (SCF) and atmospheric circulation is vital for comprehension of hemispheric-scale change mechanisms accurate forecasting. This study combined MODIS imagery with meteorological observations to investigate the variation annual SCFs in Qilian Mountains. Results indicated that more than 80% SCF distributed at high elevations mostly on northern slopes, greater west east. Abrupt increase was not detected; however, significant (0.05 confidence level) quasi-3-year quasi-5-year periods potential connection monsoons. Topographically, increased decreased valleys. Moreover, significantly a rise slope below 23° then between 45°, it aspect from 70° 200° 310°. Annual Mountains dominated by precipitation rather temperature. In years SCFs, southeasterly winds associated an anticyclone over southeastern China southwesterly cyclone Iranian Plateau brought warm moisture across northwestern China, favoring snowfall Meanwhile, cold outbreaks Arctic into mid-latitudes are conducive maintaining cover. However, low air might be difficultly transporting out region due strengthening polar vortex. water vapor less mean state divergence Mountains, which conduced