Estimation of Turbidity and Global Radiation over Jeddah in Spring@@@تقدير العكارية وإشعاع القبة السماوية فوق مدينة جدة في فصل الربيع

AUXTHAl'T. An experiment was performed for estimation of turbidity over Jeddah during Spring (March, April and May 1993). The measurements include direct. diffuse and global radiation. on clear days. The data are also incorporated ill a radiation model for estimation of different components a t'solar radiation over Jeddah, The results showed thai the turbidity and consequently the amount of aerosols in the atmosphere was maximum in April. This was accompanied by a strong south to southwest wind. The coefficient of turbidity (/f) reached (0. 9) on 6 April. a very turbid dUY . On this day. the wave length exponent ( IX) approached zero. The diurnal variation of the turbidity showed an increase started at noon and extended all afternoon The average Spring turbidity in Jedduh is (0.18). The results of the model indicate that rbe average percentage difference between the measured and the calculated direct. diffuse and global radialion are 8%. 15% and 5% respectively. The model used was successful. with an over all precision for direct and global radiation of 10% for Jeddah, This gives confidence that this model probably with some improvements. can be used for estimating global radiation over Jcddah on clear days when measurements of this parameters are not available.