SUNLIGHT, A Program to Calculate Sunshine Duration Parameters for Evapotranspiration Models

The program, SUNLIGHT, was designed and developed to determine the theoretical sunshine duration and related parameters needed to estimate evapotranspiration of crops by means of solar radiation equations. The software was written in Gw-Basic Version 2-02 to be used in a PC-DOS compatible environment. Inputs required are the latitude of the site, in degrees, and a selected period of time. Outputs are (i) mean solar declination for the period, (ii) mean value of the cosin magnitude of the sun declination parameter, (iii) average sunshine duration in light-hours per day, (iv) parameter percent of the number of light-hours per day related to annual total, (v) sunshine duration expressed as the total number of light-hours for the given period, and (vi) percent of light-hours for the study period related to the annual total