On examining daily QP/RS ratios (Fig. 2a) under cloudless skies a minimum value of 1.738 on 12/4/00 and a maximum of 2.02 mol MJ1 on 20/2/00 occur. The respective minimum and maximum values with overcast skies are 1.913 on 8/12/00 and 2.383 mol MJ1 on 16/12/01. In general, a minimum daily ratio value of 1.702 on 4/1/00 and a maximum one up to
2.388 mol MJ1 on 6/4/00 occur. The mean daily QP/ RS ratio for the whole experimental period is found to be 1.960 mol MJ1 with a standard error of the mean (S.E.) 0.044 mol MJ1, while over an individual year a mean daily ratio value of 1.967 0.031 in 2000 and 1.978 0.036 mol MJ1 in 2001, respectively, occur. The present findings are in line with Alados et al. (1996) and Jacovides et al. (2004) results for Almeria, Spain and the island of Cyprus, respectively, both sites in the
Mediterranean basin. Interestingly, comparing individual mean ratio values for May 2000–2001, 1.970 0.036 and 1.981 0.026 mol MJ1, respectively, the relative difference was as low as 0.6%; this verifies earlier mentioned remarks relating predominant wind flow patterns versus low dust-aerosol loads over the site. Further, on examining daily ratio QPd/Rd values (Fig. 2b) under clear skies a minimum value of 1.841 on 21/1/00 and a maximum of 3.204 mol MJ1 on 20/2/00 occur, whereas the respective minimum and maximum values for overcast skies were 1.447 on 11/1/01 and 2.316 mol MJ1 on 19/4/01. In general, daily ratios (QPd/Rd) range between 1.415 on 24/8/01 and 3.854 mol MJ1 on 27/1/00. The mean daily ratio value over the examined period is found to be 2.389 0.24 mol MJ1, while over an individual year mean ratio values of 2.377 0.25 in 2000 and 2.398 0.22 mol MJ1 in 2001, respectively, occur.