Abstract:
Measurement of diffuse and direct solar irradiance can be used to determine the aerosol optical properties such as an aerosols optical depth (AOD), single scattering albedo (SSA), and volume size distribution (Vol), in the atmosphere. In this study, i-skyradiometer at Observatory for Atmospheric Research at Phimai, Thailand are used to observed these properties. The period of data is between 2006-2007, Skyrad.pack V4.2 program with double precision method was used for data analysis. In 2006, on select wavelength : 500 nm, it clears that AOD and SSA value are very high in two periods, March and September. They are lower in June to July and December to January. The highest monthly average of AOD is 0.75 in March and the lowest is 0.28 in June. The highest monthly average of SSA is 0.94 in October and the lowest is 0.87 in May and June. In 2007, as in 2006, AOD and SSA value is very high in two periods, March and September. They are lower in June to July and December to January. The highest monthly average of AOD is 0.89 in March and the lowest is 0.32 in June. The highest monthly average of SSA is 0.90 in March and October. The lowest monthly of average SSA is 0.83 in December. It is found that the average volume of size of aerosol particle in coarse mode is larger than 16.54 micrometer and the size of aerosol particle in fine mode is 0.17 micrometer both of two years. The backward trajectories in winter season show the source of aerosol particle came from the north-east of Thailand, in continental. In summer season most of the aerosol particle came from the east. And in rainy season, the aerosol particle came from the south-west.
