Numerical Modelling Of West Africa Regional Scale Aerosol Dispersion

Abstract

The danger of aerosols loading in the lower atmosphere of West Africa is a source of concern both at the short or long term. Currently, there are about 45% available data sets over West Africa; hence, it is difficult to ascertain the level of threat that life forms in this region would be exposed to in the nearest future. In this thesis, it was proposed that the current challenges bedevilling the functionality of measuring devices are more of systemic error than design error. The aim of the research is to develop a comprehensive model, that is, two main and supportive models for retrieving and forecasting atmospheric aerosols in West Africa. The governing equations that was developed in the expanded Stokes' regime were resolved using analytical and numerical techniques. The unified number was derived to address the aerosols transportation inadequacies which were verified on the aerosol size distribution over some locations in West Africa. Three types of data set were used for this study; thirteen years from Nigerian Meteorological Agency datasets for six locations in Nigeria, fourteen years MISR dataset for twenty eight locations across West Africa, ten years AERONET dataset for four locations across West Africa. The new dispersion model designed in this thesis was tested on the four indicators, that is, aerosol transport in the micro scale, aerosols transport in the macro scale, aerosol size distribution, and atmospheric field application. The dispersion showed accuracy in the four listed indicators. Moving aerosols layer over West Africa travels at a speed of 8 m/s to 15 m/s. The atmospheric and tuning constants across twenty eight locations in West Africa were documented for research and industrial use. The atmospheric and tuning constants over West Africa are within the range 0.3 to 1.2 and 0.4 to 0.7 respectively. The average aerosols retention over West Africa is 30% . The aerosols retention was as high as 79% over Ouagadougou-Burkina Faso in 2002. Also the aerosols retention was as low as 0.25% over Praia-Cape Verde in 2002. The highest aerosols rentention in Ilorin and Lagos is 14.9% and 12% respectively. The accuracy of the proposed models in West Africa was within 95% confidence bounds. The standard error (SE) was 0.006216 and R-square was 0.9468. It was concluded that the current state of aerosols loading requires urgent intervention to avoid excessive heat flux like the case of India. More so, the menace of climate change may be more visible in West Africa in the nearest future if necessary policies are not in place. Salient recommendations were made to curb the long term threats to life-form.