The diffuse fraction of hourly solar radiation for Amman/Jordan

This paper presents various correlations of the hourly clearness index K-t with the hourly diffuse fraction K-d on a horizontal surface for Amman/Jordan. The first correlation is based on Orgill and Hollands method, but using weighted averages. The second correlation is based on hourly integrated values of K-t's and K-d's without any grouping. A refinement of the latter correlation is attempted by including a random shock. (C) 1998 Elsevier Science Ltd. All rights reserved.