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Title: SPATIAL AND TEMPORAL ANALYSIS OF PAN EVAPORATION IN GREECE

Author: G. Kitsara, J. Floros, G. Papaioannou, and P. Kerkides

Year: 2009

Publisher: European Water Resources Association (EWRA)

Description:

During the ongoing efforts for validating or invalidating the accelerating hydrological cycle, pan evaporation has come to the light, as an index of potential evaporation, often used together with precipitation measurements to obtain the surface moisture balance, and estimate its variability. Several studies have reported declines in pan evaporation rate throughout the Northern and Southern hemisphere for various periods since the 1950s. At individual sites, both increases and decreases in pan evaporation have also been reported. In this study, temporal analysis of daily pan evaporation measurements (Epan), Penman (ETp) and Penman-Monteith (ETp-m) evapotranspiration estimates, is presented for 16 stations in Greece, during the period 1979-1999. The high correlation between Epan and ETp-m on a yearly basis and the similarity in their annual time evolutions (in almost all stations of the study) indicate that pan evaporation can be used as an index of potential evapotranspiration in Greece, as has been reported in the literature for other regions. Furthermore, trends in Epan are examined, in order to investigate if they can represent the ETp-m trends as well. The decreasing Epan trend, reported widely in the literature, is confirmed in Greece for 10 stations, during the warm season only. In contrast, almost all stations indicate negative rainfall trends on annual, warm and cold season basis. When all stations are considered ‘as a whole’, annual, and cold season pan evaporation estimates show insignificant increases while rainfall trends are negative.