Solar Energy, Vol.61, No.4, 241-249, 1997
Atmospheric turbidity and the diffuse irradiance in Lagos, Nigeria
Values of the Angstrom turbidity coefficient, beta, at 0.50 mu m wavelength have been determined in Lagos, a tropical coastal city in Nigeria, for 17 months between 1990 and 1991 using a Volt sun photometer. The results obtained indicate high variability of aerosol loading, though the city, on average, experiences high turbidity for most parts of the year. An annual average of 0.299 with a standard deviation of 0.187 was found. On average, the month of January experienced the highest turbidity, with a mean value of 0.497, while November experienced the lowest aerosol loading on average with a value of 0.225. The aerosols influencing the city are both of maritime and Saharan origin, coupled with locally produced particulates from industries and automobile combustion. Possible effects of the Mount Pinatubo haze may be the cause of the increase of turbidity values in the second half of 1991 when compared with values for the same period in 1990. Addition of beta in the Liu and Jordan type diffuse fraction correlation indicates little improvement in standard error.