Climatology of snowfall/total precipitation days over Turkey

Abstract

Annual and regional trend of snowfall/total precipitation days (S/P) have been examined by using observation collected from 237 meteorological stations evenly distributed over Turkey. Precipitation data have been analyzed as snow and rain separately. The annual Mann-Kendall trend test has been applied to the ratios of snowfall days to total precipitation days. In the study, only winter season has been used in order to account for days with snowfall. The months for which the percentage of snowy days less than 1% of total snowy days have not been considered as winter months. During the study period, 23 different precipitation periods have been determined for the meteorological stations. The annual Mann-Kendall trend test revealed that 65 stations have decreasing trends. Following trend test applied on the basis of individual station, stations were separated into four groups in terms of their altitudes. Then, regional trend test was applied to the grouped stations. According to the results of the regional Mann-Kendall test, a decreasing trend has been observed for all regions. In order to explain the variations of the S/P days in time, we conducted the same procedure of trend analysis for temperature data. According to the trend results, statistically significant increases in winter temperatures were observed for all regions. This revealed the fact that the decrease in S/P days can be explained by the increasing trend in the temperature variations.