Decadal changes in extreme daily precipitation in Greece

P T Nastos,C S Zerefos

doi:10.5194/adgeo-16-55-2008

Abstract

Abstract. The changes in daily precipitation totals in Greece, during the 45-year period (1957–2001) are examined. The precipitation datasets concern daily totals recorded at 21 surface meteorological stations of the Hellenic National Meteorological Service, which are uniformly distributed over the Greek region. First and foremost, the application of Factor Analysis resulted in grouping the meteorological stations with similar variation in time. The main sub groups represent the northern, southern, western, eastern and central regions of Greece with common precipitation characteristics. For representative stations of the extracted sub groups we estimated the trends and the time variability for the number of days (%) exceeding 30 mm (equal to the 95% percentile of daily precipitation for eastern and western regions and equal to the 97.5% percentile for the rest of the country) and 50 mm which is the threshold for very extreme and rare events. Furthermore, the scale and shape parameters of the well fitted gamma distribution to the daily precipitation data with respect to the whole examined period and to the 10-year sub periods reveal the changes in the intensity of the precipitation.

Highlights

A great scientific interest with respect to extreme precipitation events and their economic, social and ecological implications has been aroused especially during the last decades (Karl et al, 1995; IPCC, 2001; Zhang et al, 2001)
The results show that the shape parameter of the precipitation gamma distributions remains rather stable in this period of study, independent of the total precipitation, while the scale parameter, which characterizes the scale of the intensity of the daily precipitation, is most variable (Fig. 5)
The analysis of the extreme daily precipitation totals in Greece demonstrates the existence of positive trends, not statistically significant (0.05 c.l.), observed in daily precipitation totals exceeding 30 and 50 mm at the eastern and southeastern regions of the country

Summary

Introduction

A great scientific interest with respect to extreme precipitation events and their economic, social and ecological implications has been aroused especially during the last decades (Karl et al, 1995; IPCC, 2001; Zhang et al, 2001). According to IPCC (2001), extreme precipitation is difficult to reproduce, especially for the intensities and patterns of heavy rainfall which are heavily affected by the local scale. For this reason, it is necessary to study heavy and extreme precipitaCorrespondence to: P. Regional differences are relatively high, annual precipitation trends in the 20th century, for a number of stations in Europe, exhibit a clear general positive trend for northern Europe, with the exception of Finland, and a negative for southern Europe and the Mediterranean (IPCC, 2001). Regional differences are relatively high, annual precipitation trends in the 20th century, for a number of stations in Europe, exhibit a clear general positive trend for northern Europe, with the exception of Finland, and a negative for southern Europe and the Mediterranean (IPCC, 2001). Anagnostopoulou et al (2006) studying the cyclones in the Mediterranean region, found that the Hadley Center

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Results

Conclusion