Solar radiation and evapotranspiration in northern Mexico estimated from remotely sensed measurements of cloudiness

Components of a satellite-based system for estimating the crop water requirements of irrigated vegetation were brought together, applied, and tested against field data. The operational framework for obtaining cloud cover was developed and applied, using hourly sampled, l-km resolution, GOES-7 data as received in rear time in Obregon, Mexico. The cloud-screening procedure was used to derive half-hourly estimates of solar radiation from satellite data for the Yaqui Valley irrigation scheme near Ciudad Obregon in Sonora, Mexico for the period November 1998-March 1999. Estimates were made on a 4-km grid using a high-resolution development of the Global Energy and Water-Cycle Experiment Surface Radiation Budget (GEWEX/SRB) algorithm applied with GOES-West satellite data. The values derived from the satellite data were, on average, about 9% lower than field measurements made at two sites located in the irrigated region. After re-calibration, the estimates derived from GOES-West were used to compute evapotranspiration using the Makkink equation and locally derived crop coefficients. The results show that it is possible to make high resolution near real-time estimations of crop evaporation for cotton and wheat, the two most important crops grown in the Yaqui Valley.