Climatological Analysis of Variability in Snow Cover Features Across Iran During 1981–2022

Abstract

The present study aimed to conduct a climatological analysis of snow cover variability in Iran using daily snow cover data collected from meteorological stations between 1 January 1981, and 31 December 2022. Stations were selected based on the criterion of having at least one day of snowfall over 1 cm in depth during the study period. The analysis focused on nine key indices: First snow cover day (FSC), last snow cover day (LSC), snow cover duration (SCD), mean duration of continuous snow cover (SCDmean), maximum duration of continuous snow cover (SCDmax), snow-free days (SFD), snow spell duration index (SSDI), number of snow cover events (NSC) and depth of snow cover (DSC). The temporal analysis revealed substantial variability in the FSC, ranging from October 10th in regions above 2000 m in the northwest to January 30th along the Iranian coast of the Caspian Sea. The LSC also varied from January 20 to April 20 in the low-elevation regions of the Zagros in the south to April 20 in the Alborz in the North. Moreover, the SCD was over 160 days a year in the Alborz mountain in the north. Spatial analysis indicated a significant correlation between snow cover indices and elevation, longitude and latitude in Iran's mountainous regions. Results indicated a notable increase in FSC in most parts of the country, alongside a decreasing trend in LSC. On average, FSC advanced by 2 days per decade towards winter, while LSC shifted approximately −0.82 days per decade towards winter. Additionally, SCD, NSC, DSC and SSDI exhibited decreasing trends while SFD increased.