No abstract

Aerosol index (AI) observations from the Total Ozone Mapping Spectrometers (TOMS) on board the Nimbus-7 (1979Nimbus-7 ( -1992 and Earth Probe (1997Probe ( -2004 satellites are used to investigate the annual and seasonal variations of dust haze in Sahelian West Africa. Eight synoptic stations, namely Port Harcourt (PHA), Lagos, Ilorin, Makurdi, Minna, Yola, Maiduguri and Kano, representing the four major climatic zones (tropical rainforest and Guinea, Sudan and Sahel savannahs) of Nigeria were considered in this study. Twenty-nine years of horizontal visibility data are also analysed in order to investigate the effect of dust haze on visibility in the stations under study. Results show that there are general decreasing trends in the visibility with corresponding increases in TOMS AI trends in all the climatic zones of Nigeria. This clearly suggests that there had been an increase in the integrated column dust aerosols over the years, especially during the harmattan dusty months. The average visibility was highest in Ilorin (11363.2 ± 1644.4 m) and the lowest in Maiduguri (9017.9 ± 1021.3 m) when the dust-prone months of November to March of the following year were considered. Logarithmic equations with inverse relationships are developed between TOMS AI and horizontal visibility for each station with correspondingly high coefficients of determination (R 2 ) in all the locations. It is concluded that TOMS AI can reasonably be used to reproduce visibility measurement in sub-Saharan West Africa where sparse visibility data are available for meteorological uses.

This paper considers the problem of minimizing the number of tardy jobs with release time on a single machine. Given that the problem has been classified as strongly NP-Hard, three heuristics (EOO, HR2, and HR3) are proposed for this problem. They are compared with a heuristic by Dauzere-Perez (selected from the literature). Randomly-generated problems ranging from 3 to 500 jobs are solved. Experimental results show that one of the proposed heuristics (EOO) outperforms other heuristics, both in terms of quality of solution (effectiveness) and speed of execution (efficiency). OPSOMMINGDie navorsing behandel die ministering van voltooiingstyd van die aantal draaltake by 'n enkele werktuig. As aanvaar word dat die problem geklassifiseer word as hoofsaaklike NP-hard, word voorgestel dat die vraagstuk bestudeer word deur gebruik te maak van drie heuristiese metodes (EOO, HR2, HR3). Die metodes word vergelyk ten opsigte van vertoning met die Dauzere-Perez-metode. Toevalsgegenereerde probleme wat strek vanaf 3 tot 500 draaltake word behandel. Die eksperimentele werk lewer bewys dat die EOO-metode ander metodes die loef afsteek ten opsigte van oplossingsgoedheid en -snelheid.

This study aims at analyzing the influence of rainfall and temperature on Total Column Ozone (TCO) over West Africa. It provides adequate information on the spatial variability of total column ozone concentration, temperature distribution across latitudinal zones, monthly distribution and inter-annual variability of total ozone column and interrelationship between monthly ozone and distribution of precipitation rate over West Africa. The result of this work shows that, there are significant interconnectivities between total ozone column variability with precipitation and temperature. The correlation between Annual coefficient of Relative Variation (ACRV) of Total Column Ozone (TCO) with average annual temperature and average precipitation shows that there is correlation in ACRV of total ozone column trends over West Africa with temperature and precipitation. A strong positive value correlation was observed between the ACRV of ozone and average annual temperature which increases from 25°C to 29°C at the hot arid north of the region and the mean monthly maximum ozone Coincides with the tropical summer rainfall over West Africa between June and September, which showed that there is a significant relationship between rainfall and total ozone column over West Africa. Temperature and ozone tend to increase across the latitude while rainfall decreases across the latitude. These observations suggest significant Original Research Article

The Bonny Island axis of the Niger Delta, Nigeria, is one of the most industrialized belts of Nigeria. Among the significant industries in the locality is the Nigerian natural gas liquefying plants. The plant complex generates emissions which are propagated by meteorological agents. An atmospheric dispersion model was used to model the emissions using a computer programme. A statistical analysis of meteorological parameters was also carried out to determine the pollutants dispersion in the atmosphere. The analysis shows that wind speed is moderate and the predominance of southerly winds will move plumes toward human settlements in the north and northeastern directions from the plant. From the diffusion model, the compounds likely to be emitted in the largest quantity from the plant in the order of magnitude were CO 2 , NO x , CO, PM 10 and SO x. There is evidence that pollutants concentration would be highest for receptors at about 10 km from the emission sources even under unstable atmospheric conditions. The concentration of all the pollutants were well within the set ambient limits for the averaging period considered (i.e., 1 hour). It is recommended that the LNG plants continue to use natural gas as their major fuel as it will help in reducing pollutants like CO, PM 10 and SO x. Also, due to the large CO 2 gas emitted, afforestation and conservation projects should be initiated in Bonny Island so as to earn carbon credit.