Abstract
The suitability of two simple empirical equations for the estimation of clear sky radiation was investigated. Results indicated that latitude and altitude were sufficient to estimate the empirical equation coefficients and that the estimates of evapotranspiration using the derived values of clear sky radiation were sufficiently accurate for irrigation scheduling or hydrologic modeling purposes. It was also found that there was a significant change of approximately 10% in the calibration of NOAA instruments between 1972 and 1977.
