Principal component analysis of precipitation in Thessaly region (Central Greece)

Characteristics of the precipitation pattern are determined for Thessaly region in central
Greece by using the Principal Component Analysis (PCA). Mean monthly precipitation data
from 75 meteorological stations are used covering a 35 year period (1960-1994). The first two
principal components (PCs), which describe 87.7% of the total variance, are taken into
consideration. It is demonstrated statistically that PC1 is related to the frequency of the
cyclones crossing the area, while PC2 is related to the anticyclonic and non-gradient surface
weather types and cold pools aloft. This means that PC1 explains the annual amounts of
precipitation and PC2 the summer thundery rainfalls. The spatial distribution of precipitation is
studied afterwards. Using the PCs scores, homogeneous precipitation sectors are determined
over the territory of which the annual pattern of precipitation is discussed.
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