10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Seasonal Variations of Sahara Dust and Their Impact on the Air Quality over Western Ethiopia- First Cut Results
SATHEESH M K KUMAR, Amente Dereje Wakgari, Department of Physics, Wollega University, Nekemte, Ethiopia
Abstract Number: 635 Working Group: Aerosols and Health - Connecting the Dots
Abstract Sahara is the world’s largest hot desert lying in low latitude region which spans most of northern Africa (150 to 350 N, 35 0 W to 150 E). Being the second largest arid region after Antarctica in the world and it covers about 9 million square kilometres amounting to 31% land in the African continent, the increasing amount of mineral dust emission from this region plays a pivotal role on the West African air quality and climate (Florence de Longueville et al, 2013). Despite the proximity of the Sahara, virtually no studies related with dust impact on air quality and human health have been initiated in western region of Ethiopia. As Sahara is characterized by periodical outbreaks of dust storms that transport huge amount of mineral dust in the troposphere, it can significantly enhance AOD that is correlated with the aerosol direct radiative forcing (Bart De Paepe et al, 2009, C. Zhao, et al,. 2010). Further, Saharan dust often mix with moist air transported from the Mediterranean build up sporadic clouds which in turn changes the albedo over the western Ethiopian which is lying in a hillock region. This work is a preliminary investigation of air quality variability with the seasonal changes in the direction of air mass over this region with the aid of seasonal changes in the NOAA HYSPLIT back trajectories and the respective changes in the AOD derived from MODIS. This observation further reveals the deterioration of air quality due to the transport of Sahara dust during winter months due to its eastern flow over Ethiopian region. Further, the heavy fog developed in the morning due to the shallow boundary layer across the valley during the winter months contaminated with mineral dust that causes a major health impact in this region with large population. In summer, since the influence of Indian Ocean is more pronounced over this region, the mounting level of moisture induces the development of coarse particles which can vary the weather conditions. The consistent seasonal variations of AOD derived from MODIS over Western African regions ranges from 0.24 to 0.56 reveals the progressive loading of atmospheric aerosols which is in the form different layers also drastically changes the air quality at this region as well (Mamadou Simina Drame et al, 2013). This is the first and preliminary observation from this region and quantification and characterisation of aerosols which are in progress to analyse their prominent role on the variability of air quality in this region.
References 1. Bart De Paepe and Steven Dewitte, (2009), Dust Aerosol Optical Depth Retrieval over a Desert Surface Using the SEVIRI Window Channels, J. Atmospheric and Ocean Tech.,26, 704-718. 2. C. Zhao, X. Liu, L. R. Leung, and S. Hagos, (2010), Radiative impact of mineral dust on monsoon precipitation variability over West Africa,. Atmos. Chem. Phys. Discuss., 10, 27185–27226. 3. Florence de Longueville, Yvon-Carmen Hountondji, Pierre Ozer, Béatrice Marticorena, Bernadette Chatenet & Sabine Henry (2013), Saharan Dust Impacts on Air Quality: What Are the Potential Health Risks in West Africa?, Human and Ecological Risk Assessment: An International Journal, 19:6, 1595-1617, DOI: 10.1080/10807039.2012.716684. 4. Mamadou Simina Drame, Moctar Camara, Amadou T. Gaye, (2013), Intra-Seasonal Variability of Aerosols and Their Radiative Impacts on Sahel Climate during the Period 2000-2010 Using AERONET Data, International Journal of Geosciences, 4, 267-273.
Key Words: dust, air quality, radiative forcing, West Africa.