INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. 21: 467–481 (2001) DOI: 10.1002/joc.620 INFLUENCE OF SYNOPTIC SITUATIONS ON THE PRECIPITATION IN KRAKO ´ W (POLAND) ROBERT TWARDOSZ a, * and TADEUSZ NIEDZ ´ WIEDZ ´ b,c a Department of Climatology, Jagiellonian Uniersity, Grodzka 64, 31 -044, Krako ´w, Poland b Department of Climatology, Uniersity of Silesia, Bedzinska 60, 41 -200 Sosnowiec, Poland c Institute of Meteorology and Water Management, Borowego 14, 30 -215 Krako ´w, Poland Receied 3 May 2000 Reised 3 October 2000 Accepted 13 October 2000 ABSTRACT The impact of the synoptic situations on the occurrence of precipitation in Krako ´ w is analysed. Daily records of precipitation from the period 1873–1999 were used, as well as the calendar of synoptic situations by T. Niedz ´wiedz ´. The study presents annual and long-term variations of daily precipitation, frequency of the synoptic situations, and frequency of precipitation for particular situations. For the 21 types of synoptic situations, the following characteristics were defined: average daily precipitation and its effectiveness ratio, maximum precipitation and the probability of occurrence of days with or without precipitation. Most precipitation occurs during the advection of air masses from the west and during the cyclonic trough, which is related to high frequency of occurrence of such situations. From among 21 synoptic situations, the following ones are the most favourable for the development of abundant precipitation: northeastern cyclonic situation (NEc), north cyclonic situation (Nc), cyclonic trough (Bc) and centre of low pressure (Cc). Copyright © 2001 Royal Meteorological Society. KEY WORDS: circulation patterns; daily precipitation; Poland; synoptic situations 1. INTRODUCTION In climatological literature, precipitation, as well as air temperature, is considered to be an important index of climatic changes caused, for example, by the increase in the carbon dioxide content of the atmosphere (Bradley et al., 1987). Precipitation is a discontinuous element in time and space, largely conditioned by local situation. Analysis of long-term data for a particular site gives us information on point, past climatic conditions, and forms the basis for all climatic forecasts. The Meteorological Station at the Climatology Department of the Jagiellonian University in Krako ´w is one such important centre, with a continuous series of records. It is one of the longest series of measurements in central Europe, taken at the same place since the late eighteenth century (Figure 1). Owing to the length of the series, Krako ´ w station is a reference site for the analysis of the evolution of climate in central Europe (Obre ˛bska-Starklowa, 1993), especially as the precipitation variability in Krako ´ w in certain periods correlates with precipitation changes in other stations of the region (Twardosz, 1996). To date, the studies concerning precipitation variability in Europe have not taken into account the Krako ´ w series (Dahlstro ¨ m, 1994; Scho ¨ nwiese and Rapp, 1997). Measurements of precipitation amounts in Krako ´ w began in August 1849, and have continued since at the same location. Since the station’s foundation in 1792, the results of many visual observations were gathered, including precipitation occurrence. Relying on the close statistical interdependencies between the number of days with precipitation and the precipitation amounts, the monthly and annual totals for the * Correspondence to: Department of Climatology, Jagiellonian University, Grodzka 64, 31-044, Krako ´w, Poland; e-mail: rtwardo@grodzki.phils.uj.edu.pl Copyright © 2001 Royal Meteorological Society