This research aims to calculate the solar radiation attenuation due to aerosols in the atmosphere of Thailand. The investigation was based on comparison of the clear day solar radiation obtained from measurements and from the model which excludes the effect of aerosols. The solar radiation attenuation obtained from this investigation was used to formulate a model relating the aerosol attenuation to the collected visibility data. Then the model was employed to calculate the aerosol attenuation at eighty-five meteorological stations nationwide where visibility data are available. Results obtained from the calculation show that the aerosol attenuation varies by time of year. In the dry season is high and in the rainy season is low. The average for the year was 0.1673 ± 0.0022.
