Calibration of the potential evapotranspiration product "MOD16A2" for the Argentinian Pampas Region

Evapotranspiration (ET) is the hydrological variable with the greatest relevance in the Argentina Pampas Region (APR), because through this process a large part of the water that enters as precipitation is lost from the system. Knowing the spatial variability of the ET is essential to be able to include it in hydrological models. An alternative is the use of satellite products. In previous papers, the MOD16A2 product of potential ET (ETp) was evaluated, comparing it with in situ data of twenty-four stations distributed in the APR in 2012, 2013 and 2014, with a total of 3,094 pairs of analyzed data, observing a higher over estimation of 50% throughout the period which could be attributed to the error in the term of net radiation in the ETp equation. Using the same database, in this paper the systematic error found in the MOD16A2 product was corrected by means of a linear regression, using 60% of the data pairs ETp (MOD16A2) of in situ data to calibrate the model and the remaining 40% for its validation. The results showed a decrease in the mean square error of 2.4 to 0.6 mm day(-1) and the mean absolute error of 2.2 to 0.5 mm day(-1). After correction, the MOD16A2 product improves significantly and can be used for hydrological purposes at the basin scale. It is recommended for evaluating the method in large basins and in other regions of the world to determine if there are systematic errors, and eventually correct them following the procedure proposed here.