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Communication incl. Poster: BibTeX citation key:  Sunnu
Sunnu, A. K., Afeti, G. M. & Resch, F. 2009. Saharan dust particle size and concentration trends in Ghana. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: Devic 2009-09-10 15:10:30
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Categories: Aerosol and Chemistry, Atmospheric processes
Keywords: Aerosol, Chemistry
Creators: Afeti, Resch, Sunnu
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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Abstract
The Saharan dust that is transported and deposited over many countries in the West African atmospheric environment (5°N), every year, during the months of November to March, known locally as the Harmattan season, have been studied over a 13-year period, between 1996 and 2008, using a location at Kumasi in central Ghana (6° 40′N, 1° 34′W) as the reference geographical point. The suspended Saharan dust particles are sampled by an optical particle counter.
The counter gives the total dust loads as number of particles per unit volume of air. The optical particle counter used did not discriminate the smoke fractions (due to spontaneous bush fires during the dry season) from the Saharan dust.
The size range covered by the optical particle counter was 0.5 μm–25 μm. The Sahara dust particle size distributions and concentrations are analysed. Within the particle size range measured (0.5 μm–25 μm.), the average inter-annual mean particle diameter, number and mass concentrations during the northern winter months of January and February were determined. The average daily number concentrations ranged from 15 particles/cm3 to 63 particles/cm3 with an average of 32 particles/cm3. The average daily mass concentrations ranged from 122 μg/m3 to 1344 μg/m3 with an average of 548 μg/m3.The measured particle concentrations outside the winter period were consistently less than 10 cm-3. The overall dust mean particle diameter, analyzed from the peak representative Harmattan periods over the 13-year period, ranged from 0.89 μm to 2.43 μm with an average of 1.5 μm ± 0.55. The particle size distributions exhibited the typical distribution pattern for atmospheric aerosols with a coarse mode diameter situated at about 3.5 μm. The experimental results reported in this study will be important in validating satellite based observations and simulation models of the African dust plume towards the Gulf of Guinea during winter.
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