Solar net radiation over a bare wet field at Giza, estimated on the basis of its close relationship with global radiation

Abstract

A comparison was made between daytime, night-time and daily net radiation measured in different seasons over a bare wet field at Giza, and the corresponding values of net radiation over irrigated short vegetation and global radiation. Close linear relationships were obtained in all cases. The relations with daytime and daily global radiation were applied to monthly averages of daily global radiation for a 10-year period, to obtain monthly averages of daily and daytime net radiation over the bare wet field. The annual variations of these variables, together with night-time net radiation obtained as the difference between these values, are described. Seasonal and annual values of these parameters, together with monthly, seasonal and annual values of the ratios of net radiation over the wet field to global radiation, and of net radiation over the same field to net radiation over irrigated short vegetation were also given. The corresponding values of the ratio daytime/daily net radiation over the wet field were also obtained to give an idea of the diurnal variation of net radiation in the different seasons. Brief information was also given about the highest and lowest values of net radiation during the day, and their times of occurence.