An investigation of sky radiance from the measurement at a tropical site

The sky radiance was measured by using a sky scanner (EKO, model MS-321LR) at a tropical site in Nakhon Pathom (13.82° N, 100.04° E), Thailand. A three-year period of sky radiance data was analyzed. Sky radiance distribution for each season was investigated. The results showed that the monsoons had strong effect on the sky radiance distribution. The hourly clear sky radiance from the measurements was also compared with that obtained from the corresponding sky radiance calculated from the CIE model, which considers two different standard clear sky types. It was found that the measured and calculated sky radiances were in reasonable agreement, for both cases.