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Impact of Dry Air Intrusion During the Monsoon West Africa: The Case Study of 23–24 July 2012 in Dakar, Senegal

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Abstract

This work concerns the rainy season delay in Western of Africa toward Dakar area in the country of Senegal. Since 2006, continuous dry air intrusions from Western Sahara have been recorded in the lower layers at the beginning of the monsoon season from Western Sahara. This dust by indirect effect tends to inhibit convective systems. Here, we present one among several cases where convection was inhibited by dry air intrusions near the coastlines in 2012 between 23 and 24 July in Dakar, Senegal. Meanwhile, Tambacounda (East of Senegal) recorded 75 mm of rainfall, unlike Dakar where there has been only traces of rain. For these days, the convective activity monitoring is carried from ORL data and METEOSAT images. The in situ data, such as radiosondes and lidar pictures, clearly show that the dry air is located in the low layers between 200 and 400 m. The AERONET data confirm that this dry layer is composed of dust with 2.2 microns of size. HYPLIT-4 back-trajectory model and NCAR/NCEP reanalysis indicate that the dry air in Dakar area is from Western Sahara (Morocco). They also show subsiding movements, accompanied by a strong North wind and a weak Easterly wind during these 2 days in Dakar. The results of this study clearly show that the dry air tends to slow down the Eastern movements of waves and inhibit some convective cells like those of July 23–24.

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Authors and Affiliations

  1. LPAO-SF, ESP-University Cheikh Anta Diop, Dakar, Senegal

    Sémou Ndao, Daouda Badiane, Mamadou Simina Drame & Saïdou Moustapha Sall

  2. Department of Physics, FST, Université Cheikh Anta Diop de Dakar, Dakar, Senegal

    Mamadou Simina Drame

  3. Department of Physics, Faculty of Science, University of Douala, Douala, Cameroon

    Andre Lenouo

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  1. Sémou Ndao
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  2. Daouda Badiane
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  3. Mamadou Simina Drame
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  4. Andre Lenouo
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  5. Saïdou Moustapha Sall
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Correspondence to Sémou Ndao.

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Ndao, S., Badiane, D., Drame, M.S. et al. Impact of Dry Air Intrusion During the Monsoon West Africa: The Case Study of 23–24 July 2012 in Dakar, Senegal. Aerosol Sci Eng 5, 156–165 (2021). https://doi.org/10.1007/s41810-021-00092-8

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  • DOI: https://doi.org/10.1007/s41810-021-00092-8

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