2. Data and analysis2.1. Climatolog

2. Data and analysis
2.1. Climatological data
In this study, the climatological data used in the analysis concern monthly values of air temperature and precipitation from 28 meteorological stations for the period 1951 to 2000. The 22 meteorological stations concern stations that belong in the Hellenic National Meteorological Service (HNMS), while the data of the rest stations from neighboring countries were acquired from the climatic base “Monthly Climatic Data for the World”. The use of data from stations abroad was considered in order to improve the spatial interpolation in the region of Greece. The homogeneity of the air temperature and precipitation data of our stations has also been studied in previous publications and they are considered homogeneous (Peterson et al., 1998, Xoplaki et al., 2000, Xoplaki et al., 2004, Feidas et al., 2004, Feidas et al., 2007, Nastos and Matzarakis, 2008 and Philandras et al., 2008). In the process, the mean monthly and annual values for each decade (1951–1960, … 1991–2000) were calculated. The geographical distribution of the meteorological stations is shown in Fig. 1. Specifically, the processing of climatic data was done by using the statistical package R-project and the Geographical Information Systems (GIS, ArcInfo 9.2).