The use of hierarchical cluster analysis for grouping atmospheric precipitation in Poland

The aim of this study is to present the application of statistical methods to assess the possibility of grouping precipitation according to their elevation above sea level and precipitation levels in the temperate climate of Poland. The country was divided into regions with similar levels of precipitation using cluster analysis by Ward’s method. The study was performed with meteorological data on average monthly precipitation of 53 meteorological stations from 1981 to 2010. The selection of stations was dictated by the need to consider the variability in amounts of annual precipitation throughout the country. The data was used to calculate average annual precipitation total as well as average precipitation total in the summer half-year (from May to October) and the winter half-year (from November to April) for Poland, from 1981 to 2010. Statistical method was performed and six clusters were generated, for the elevation of the stations and average annual precipitation as well as average precipitation for hydrological half-years. The average annual precipitation for the clusters ranged from 530 mm (cluster 5) to 820 mm (cluster 2). The average precipitation for the winter hydrological half-year ranged from 190.1 mm (cluster 1) to 288.8 mm (cluster 5). The average precipitation for the summer hydrological half-year ranged from 326.3 mm (cluster 5) to 605 mm (cluster 2). The conclusions from the analysis carried out in the study are that: (1) grouping by means of Ward’s method can be used to distinguish homogeneous areas with the same levels of precipitation; (2) both precipitation and the elevation, at which meteorological stations are located, are the basis for distinguishing clusters in Ward’s method.