Estimating Eto using Penman-Monteith FAO model with minimum data integrated with a Geographic Information System

Abstract

The objective of this work was to evaluate Et_oPM using limited climate data integrated with a Geographic Information System in the Jaguaribe basin, Ceará State, Brazil. Regional climate modeling system PRECIS (Providing Regional Climates for Impacts Studies), using boundary conditions of the Hadley Centre Atmospheric Model version 3 - HadAM3, nested to the Hadley Centre Regional Circulation Model - HadRM3P, was used. Monthly time series for minimum and maximum temperature and rainfall were generated for the 1961-1990 period. Variables were analyzed according to spatial variability using kriging geostatistics methodology. A validation was performed, correlating Et_oPM estimated with minimum data and with a complete dataset from a reference weather station by linear regression. Average annual estimated Et_oPM was 1,719 mm, mapped over the target region. It was demonstrated that the limited data methodology worked satisfactory for the region (linear coefficient of 0.95, determination coefficient of 0.902, errors less than 0.45 mm day^-1 and root square error of 0.067 mm day^-1).