Premium
Solar radiation in dense saharan aerosol in Northern Nigeria
Author(s) -
Brinkman A. W.,
McGregor James
Publication year - 1983
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49710946210
Subject(s) - aerosol , environmental science , turbidity , atmospheric sciences , irradiance , visibility , diurnal temperature variation , climatology , meteorology , geography , physics , geology , optics , oceanography
Measurements of normal incidence and global irradiance were made during the periods November to December 1977 and November 1978 to February 1979. Aerosol density was monitored in terms of turbidity, derived from the normal incidence record. A daily mean turbidity was calculated and used to trace variations in aerosol density over the season. Values ranged from 0–09 to 2–16 with average values of 0–44 and 0–47 for the two measurement periods respectively. A simple model was devised which related the diffuse irradiance to the turbidity and a parameter which described the angular dependence of scattering. This model demonstrated that significant differences existed between the optical properties of the local background aerosol and the dense Saharan aerosol periodically transported by the Harmattan wind. One such period of dense aerosol, when the visibility was reduced throughout most of Nigeria, is presented as a case study. The reduction was particularly severe in the north, where visibility fell below 500 m and an associated drop in air temperature of up to 6 °C occurred. Diurnal variations in turbidity were observed during periods of dense aerosol, although during the clearer periods diurnal variations were not evident. Some broad‐band spectral measurements of normal incidence irradiance were taken which indicated that extinction in both the dense Saharan and background aerosols was spectrally neutral.