Abstract:
A study on the Spatial Distribution of Harmattan Dust (Aerosol) Loading on Horizontal Visibility
over Northern (lat. 80N-140N and long. 30E-150E) Nigeria was carried using thirty (30) years
visibility, Community Earth System Model Aerosol Optical Depth (CESM AOD) and Spatial
pattern of near surface (925hpa) wind field for the month of November -March. Twelve (12)
stations were considered in this research based on the availability of horizontal visibility data for
the research period. The study aims at analyzing the spatial distribution of harmattan dust (aerosol)
loading on horizontal visibility over the study area during the period of thirty (30) years. The
spatial distribution of harmattan dust haze over the region was obtained using the inverse distance
weighted method from the from the spatial analytical tool on Arch GIS to pict the distribution
pattern of the CESM AOD. The spatial pattern of near surface wind field over the Northern,
Nigeria was determined using Era-Interim Reanalysis datasets for the daily mean Zonal U and
Meridional V components. The horizontal visibility data obtained from Nigerian Meteorological
Agency (NIMET) was also computed to depict the variation over the period. The mean monthly
visibility peaks in the month of March and decreases significantly again with corresponding
increase in CESM AOD across the selected station. Aerosol build up begin in the month of
November and continues across the months which peak in January and thereafter begins to decline
across the months. Visibility is seen to be higher in November with a lower Aerosol and reduces
across the months with increasing aerosol. The average visibility mean (Geographical mean) for
the 30 years is found to be approximately 12.64km across the study area, with Kebbi state (Nguru)
having the highest visibility (19.5km) and Abuja the least visibility (7.64km). The Station visibility
is generally lower than the average visibility (Geographical mean) across the study areas
