Weather types in Sosnowiec (Poland) during the period 1999-2013

The study presents the structure of weather types for the city of Sosnowiec during the period 1999-2013. The analysis was carried out on the basis of daily thermal data (the average daily air temperature, the minimum and maximum daily air temperature), cloudiness and precipitation. The data was obtained from a meteorological station belonging to the Department of Climatology at the Faculty of Earth Sciences at the University of Silesia. Weather types were established according to weather type classification after Woś (2010). 48 weather types were specified on the basis of a combination of 3 selected meteorological elements (temperature, cloudiness, precipitation). The number of days in the year and the frequency of particular thermal weather types, weather subtype, weather classes and weather types were characterized, and the changeability of weather types was analyzed. Furthermore, sequences of days with specific weather types were described. The analysis conducted has lead to the conclusion that, during the research period, the weather structure for the city of Sosnowiec was characterized by a great number of weather types observed, with relatively low frequency of occurrence. Weather throughout the year was dominated by warm weather types (3--, 2--, 2--), with weather marked as 310 – very warm, moderately cloudy, without precipitation (12.9%) recorded as the most frequent, followed by 221 – moderately warm, very cloudy, with precipitation (11.6%), and 210 – moderately warm, moderately cloudy, without precipitation (11.4%)as the least frequent one. A diversification in the number of particular classification units in consecutive years of the examined 15-year period does not display significant variability. Short sequences of 2 and 3 days dominated the selected sequences of specific weather types.