REFERENCE CROP EVAPOTRANSPIRATION OVER GREECE

Monthly evapotranspiration (ET) estimates for 31 locations in Greece are calculated by the Penman, Priestley-Taylor and Thornthwaite methods. The analysis of 27 years of routine meterological data indicates that annual amounts of ET obtained by Priestley-Taylor or Thornthwaite methods do not generally agree very well with Penman ET (ET(PEN)) predictions. There are some advantages of using Priestley-Taylor over Thornthwaite method but both underestimate ET compared with Penman estimates. Priestley-Taylor's and Thornthwaite's monthly estimates are very close to ET(PEN) for the wet stations and underestimate ET(PEN) to a great degree for the medium wetness and dry stations. The methods give widely different results during the winter months and during the dry season when the "etesians" (high local winds) prevail, especially in Eastern Greece.