West African weather is largely controlled by the annual north-south oscillatory movements of the Inter Tropical Discontinuity (ITD), an imaginary line that separates cool maritime equatorial south-westerly wind from hot continental north-easterly wind. ITD reaches its northern-most (22°N) and southern-most (4°N) positions during the months of August and January respectively. Deep convective systems responsible for about 95% of Sahelian precipitation frequently occur at about 150Km to the south of ITD. To the north of the ITD, winds are north-easterly at all levels and the situation is hazy weather conditions at all time. This dust laden haze is the major natural pollutant in West Africa. The dust that affects West Africa is raised mainly from Faya-Largeau (Chad Republic, WMO station number 64573) and Bilma (Niger Republic, WMO station number 61024). The dusts are normally confined to the lower level of the atmosphere by the temperature inversion; therefore, it is dangerous to human health. It also impairs both horizontal and vertical visibility. Chemical analysis of dust-haze showed a high content of metals. These made the dust to be very influential on the socio-economic well-being of West Africans, ranging from health, transportation (land and air), agriculture, energy/power and commercial activities such as buying and selling.
HEALTH
Information from state medical centers revealed that about 75% of the population reacts to dust-haze. People affected most are those that are allergic to dust. It is also found that only about one-third of the people that reacted health-wise visit hospitals to lodge complaints about one or more ailments. Statistics show that more patients go for medical consultation in January which is the peak period of the Harmattan dust-haze. The most frequent illnesses complained of during harmatan dust-haze are upper-respiratory-core infections (cough, catarrh, cold, etc), pneumonia, skin irritations, typhoid and other water-borne infections. Minor ailments are cracked lips, headache, frequent sneezing, etc. These health vices are common among infants under 4 years old and adults above 60 years old, because they have lower immunity.
AGRICULTURE
This aspect of economics is the most affected as agricultural activities are virtually brought to a halt. During this season, moisture is driven away from all surfaces, plants inclusive, because this dust-laden air is dry. The relative humidity and dew point characteristically fall below 20% and 15 °C respectively. Irrigation fed farms are not spared as irrigation water dries up or falls below convenience levels. Only the drought resistant plants survive this period. Harvested and stored farm products are forced-ripen or they dry off and become unfit for consumption. Obviously, this is a revenue-suffocating period.
LAND TRANSPORTATION
The major effect here is that visibility is largely reduced to an unfavorable extent. This forces transporters to reduce their speed, resulting in longer travel time, hence loss of revenue. This frequently led to stranding and accumulation of travelers / passengers at terminus.
AVIATION
Private and commercial airlines are greatly affected as a result of deterioration in visibility below operational levels. Dust-haze persistence with its poor visibility results in flight delays, diversions or outright cancellations. Minimum operational visibility for most airports in West Africa is within 800 to 1200m. However, visibility could fall well below 500m for days in some airports.
COMMERCIAL ACTIVITIES
Periods of Harmattan dust-haze allow unhindered buying and selling activities. Pharmaceutical, cosmetics and textile / clothing industries / sectors enjoy these periods most. These industries record high profits.
ENERGY AND POWER
About 90% of electrical energy in West Africa is hydro-generated through construction of dams across rivers which are mainly fed by rain. During this period in question, water levels may fall below operational levels. This results in power failures and rationing of power to consumers. Homes, industries and offices are greatly affected by these negative developments, as they result in loss of comfortability and revenues.
Sub-Saharan Africa depends more on its environmental based resources for its economic and social needs than any other region in the world; therefore, national activities as well as trading patterns are intimately linked with climate. It is concluded that Harmattan dust-haze provides both enabling and disturbing grounds for economic activities.
REFERENCE
Omogbai, BE 1999. Socio-economic aspects of climate change. Proceedings of the
National Climate Conference of the Nigeria Met. Dept., Lagos, Nigeria.
Green, JR 1970. A generalized probability model for sequence of wet and dry day.
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Omotosho, JA 1992. Long-range prediction of the onset and end of the rainy season in the West African Sahel. Int. J. of Clim., vol.12, 369.