Abstract :
Nine correlations have been developed in this paper to estimate the monthly average diffuse radiation for Dakar, Senegal.
A 16-year period data on the global (H) and diffuse (H ) radiation, together with data on the bright sunshine hours (N), the d
fraction of the sky’s cloud cover (Ne/8), the water vapour pressure in the air (e) and the ambient temperature (T ) have been
used for that purpose. A model inter-comparison based on the MBE, RMSE and t statistical tests has shown that estimates in
any of the obtained correlations are not significantly different from their measured counterparts, thus all the nine models are
recommended for the aforesaid location. Three of them should be particularly selected for their simplicity, universal
applicability and high accuracy. Those are simple linear correlations between K¯ and N¯/N¯, N¯e/8 or K¯. Even presenting d d t
adequate performance, the remaining correlations are either simple but less accurate, or multiple or nonlinear regressions
needing one or two input variables.
2003 Elsevier Ltd. All rights reserved.
