Pennan's relerence evapotranspirationeslirnateswithsinPleslOWcO$tifl5lrUmefltsfOrfam1e

Abstract

The estiniates ol Penman's reterence evapotranspiralion (ETo) obtained froni observations of wet and dry bulb therrnometers, sunshine recorder and anemometer were compared lo Pennan's estimates obtained from values of class A pan and Piche evaporimeters and maximum and minimum airthemiometers. In the later, global solar radialion was obtained trom a simple linear regression between global solar radiaifon measured with a piranometer and class A pan evaporation, with a R 2 = 0,66. The R2 between the two es' timates was 0,93. ETo estimates lrorn class A evaporation were less correlated with Penman's esímales using the traditional insbuments with a R 2 = 0,73. The proposed methodology requires much cheaper inslruments than lhe traditionally ones used lorthis purpose and are very simple to be managed by farniers,