The effect of climate change on snowfall and its prediction in Hamadan county

This research aimed at investigating and predicting snowing changes in Hamedan region using MODIS satellite data and images, harmonic analysis and micro-scaled atmospheric data. The study used Hamadan station data, satellite images and the NDSI index during the 30 years (1992 to 2022), analyzed the trend of snowfall changes, and modeled and predicted for the next 20 years. The analysis of satellite images and the NDSI index showed that the snow cover in Hamadan city has significantly decreased. This amount, compared to the area of the city, has decreased from about 20% of the snow cover to about 7% over the decade. Also, the variance value in the first harmonic coefficient during the statistical period is about 75%, which refers to seventy-five percent of snowfall in the region. The variance of the second harmonic coefficient is 20 percent, which implies the effect of Alvand Mountain and the height of the region on snowfall. In recent years, this amount has reached 27 percent, indicating a decrease in large-scale synoptic systems' contribution. It also shows climate changes and warmer winters. The maximum snowfall in the first harmonic is 16.2 centimeters, which has decreased to 13.2 centimeters in recent years. In recent years, the phase angle or the time of maximum snowfall has changed from mid-fall to early winter. The LARS micro-scale model was used to predict and scale the data of the atmospheric general circulation model (HadGEM2-ES) and the Coupled Model Inter-comparison Project (CMIP5). The results showed that Hamadan has been facing a decrease in snowfall and warmer winters in recent years.