Solar radiation reduction by water and dust in the Area of Thessaloniki

In the present work, an attempt is made to present the realistic condition of the atmosphere over the city of Thessaloniki by comparing the direct solar radiation reaching the city centre with the solar radiation reaching the rural areas. The comparison is made possible by making use of the values of direct solar radiation and of turbidity factors, such as the Linke turbidity factor Tg or the Angstrom turbidity coefficient β. The values of direct solar radiation which were measured inside the city were significantly lower than the ones measured out in the rural area. It has been found that the direct solar radiation in the city exhibits a reduction of the order of 10–20%. The reduced values of direct solar radiation measured inside the city are sometimes due to the increased concentration of dust particles and sometimes due to the increased quantities of water vapour coming from Thermaikos bay and diffused in the atmosphere.