Analysis of sky condition using solar radiation data at Kwangju and Seoul, South Korea and Ile-Ife, Nigeria

Summary ?Daily global and diffuse radiation measurements have been used to characterize the atmosphere optical conditions at Kwangju (Lat.35.13N, Long.126.53E) and Seoul (Lat.37.57N, Long.126.98E) in South Korea and Ile-Ife (Lat.7.14N, Long.4.56E) in Nigeria. The clearness index, (CI) which gives the percentage depletion by the sky of the incoming global radiation and the diffuse ratio, (D_R) which represents the effectiveness of the sky in scattering incoming radiation have been analyzed in this study. Results show an average clearness index value of 0.57 for the year 1999 with maximum values occurring during the wet seasons at Ile-Ife. The average clearness indexes for Kwangju and Seoul from 1998–2000 was 0.48 and 0.34, respectively, with both stations having maximum clearness indexes in the winter seasons. The diffuse ratio was higher at Kwangju and Seoul than at Ile-Ife due to heavy dust pollution from the Gobi desert in the Korea peninsula in spring, and high biomass burning at Kwangju in the fall. Department of Physics, Obafemi Awolowo University, Ile-Ife, Nigeria Received May 7, 2001; Revised November 24, 2001