Time variation in solar radiation in the negev, israel and its possible relation to the el chichon volcanic dust cloud

Extensive measurements of solar radiation at Sede Boqer, Israel revealed considerable changes in the direct and diffuse solar irradiance on clear days beginning in September 1982. The direct beam irradiance showed a consistent decrease of about 10 per cent compared to clear‐day values of the previous year. The diffuse irradiance data showed an increase of about 50 per cent and the ratio between diffuse and global irradiance increased by 63 per cent. The prominent effects were observed from autumn 1982 to spring 1983. Weak effects were still noticeable in winter 1983/1984 although a tendency of back to ‘normal’, though not quite, is evident in spring and summer 1984. Another interesting result of the analysis is that only very small changes in global irradiance were evident. These observations may be attributed to the El Chichon dust cloud since they are in accord with various types of measurements made of the dust cloud in other areas of the world.