Spatial variability of reference evapotranspiration in Greece
Optimal interpolation using geostatistical techniques, such as kriging, can be used for contouring and mapping of regionalized variables. In this study spatial variability of reference evapotranspiration over Greece is investigated using geostatistics. An exponential semivariogram model with only one pair of drift coefficients is used as the most appropriate fitted theoretical model. Kriging estimates of reference evapotranspiration rates and kriging variance have been conducted at 380 locations covering the Greece in a square grid mesh of 50 km. The results are used to plot contour maps of mean monthly and annual total reference evapotranspiration rates as well as contour maps of the kriging variance. Mapping of reference evapotranspiration and of kriging variance all over Greece is implemented as an agroclimatic parameter. The plotted results have been used to identify the spatial characteristics of evapotranspiration along several directions. Moreover, the impact of the main topography and climatic features in Greece to the analysis results is examined. Verification of the reference evapotranspiration kriging estimates is also performed. Numerous comparisons show that the results of the verification procedure are acceptable, thus suggesting that geostatistics can be used for the description of the spatial variability and for agroclimatic mapping of reference evapotranspiration over large regions with complex terrain such as Greece. Moreover, the analysis results and mapping of reference evapotranspiration can be used for agroclimatic purposes and design. (C) 2002 Elsevier Science Ltd. All rights reserved.