Variability and trends in the duration and depth of snow cover in Poland in the 20th century

This study investigates the changes and variability of the number of days with snow cover of ≥1 cm depth and the seasonal maximum snow cover depth at 66 meteorological stations throughout Poland, spanning a period of 50 (1948–49 to 1997–98) to 108 (1895–96 to 2002–03) winter seasons. A slight decreasing trend was observed with snow cover characteristics in most of Poland during the second half of the 20th century, but no change was distinguished for the longer periods. The snow cover changes are related to circulation changes, and particularly to the increased frequency of western advection over Poland. However, the scale of the snow cover change is not proportional to the air temperature changes, which have been found in many previous studies to display an increasing statistically significant trend in winter. An increasing trend of snow cover in the last 50 winter seasons is observed in areas with abundant snow cover only, i.e. in northeastern Poland (snow cover depth) and in the mountains (snow cover duration). In lowland areas of Poland the snow cover duration indicates an 8 year periodicity. The year‐to‐year variability of snow cover has been increasing, particularly during the second half of the 20th century.