In this study, the long term trend of the observed visibility data used directly (without conversion into dust concentrations) over Sahel was investigated between 1957 and 2013. Then, to review the influence of atmospheric factors and land surface conditions on this trend, the coevolution between the visibility and the dust surface mass concentration from MERRA-2 (Modern-Era Retrospective analysis for Research and Applications) reanalysis, the in-situ surface meteorological data (rainfall, relative humidity, wind speed, and air temperature), as well as the Normalized Difference Vegetation Index (NDVI) were analyzed from 2000 to 2013. We showed that the horizontal visibility has significantly decreased since the 1970s. The coevolution between the visibility and the dust surface mass concentration revealed that visibility decreased significantly with increments in dust concentrations. Visibility increases with rainfall and relative humidity. It is greater in areas of high vegetation cover than in deforested areas. Visibility is weakly correlated with wind speed and air temperature but generally, wind leads to a decrease in visibility, while warm air temperature is associated with a clearer sky and hence, high visibility. The worst visibility in the dry season results from high dust concentrations due to warm and dry wind conditions and less vegetation cover. Rainfall, relative humidity and vegetation cover are the dominant factors contributing to the decrease of dust loading in the Sahel.
References
[1]
Rosenfeld, D., Rudich, Y. and Lahav, R. (2001) Desert Dust Suppressing Precipitation: A Possible Desertification Feedback Loop. Proceedings of the National Academy of Sciences of the United States of America, 98, 5975-5980.
https://doi.org/10.1073/pnas.101122798
[2]
Ridley, D., Heald, C. and Prospero, J. (2014) What Controls the Recent Changes in African Mineral Dust Aerosol across the Atlantic? Atmospheric Chemistry and Physics, 14, 5735-5747. https://doi.org/10.5194/acp-14-5735-2014
[3]
Chen, S., Jiang, N., Huang, J., Xu, X., Zhang, H., Zang, Z., Huang, K., Xu, X., Wei, Y., Guan, X., et al. (2018) Quantifying Contributions of Natural and Anthropogenic Dust Emission from Different Climatic Regions. Atmospheric Environment, 191, 94-104. https://doi.org/10.1016/j.atmosenv.2018.07.043
[4]
Stocker, T.F., Qin, D., Plattner, G.K., Alexander, L.V., Allen, S.K., Bindoff, N.L., Bréon, F.M., Church, J.A., Cubasch, U., Emori, S., et al. (2013) Technical Summary. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, 33-115.
[5]
Choobari, O.A., Zawar-Reza, P. and Sturman, A. (2014) The Global Distribution of Mineral Dust and Its Impacts on the Climate System: A Review. Atmospheric Research, 138, 152-165. https://doi.org/10.1016/j.atmosres.2013.11.007
[6]
Prospero, J.M. and Lamb, P.J. (2003) African Droughts and Dust Transport to the Caribbean: Climate Change Implications. Science, 302, 1024-1027.
[7]
Cowie, S.M., Knippertz, P. and Marsham, J.H. (2013) Are Vegetation-Related Roughness Changes the Cause of the Recent Decrease in Dust Emission from the Sahel? Geophysical Research Letters, 40, 1868-1872. https://doi.org/10.1002/grl.50273
[8]
Doherty, O.M., Riemer, N. and Hameed, S. (2014) Role of the Convergence Zone over West Africa in Controlling Saharan Mineral Dust Load and Transport in the Boreal Summer. Tellus B: Chemical and Physical Meteorology, 66, 23191.
[9]
Evan, A.T., Fiedler, S., Zhao, C., Menut, L., Schepanski, K., Flamant, C. and Doherty, O. (2015) Derivation of an Observation-Based Map of North African Dust Emission. Aeolian Research, 16, 153-162. https://doi.org/10.1016/j.aeolia.2015.01.001
[10]
Huneeus, N., Schulz, M., Balkanski, Y., Griesfeller, J., Prospero, M., Kinne, S., Bauer, S., Boucher, O., Chin, M., Dentener, F., et al. (2011) Global Dust Model Intercomparison in AeroCom Phase I. Atmospheric Chemistry and Physics, 11, 7781-7816.
https://doi.org/10.5194/acp-11-7781-2011
[11]
Davis, R.E. (1991) A Synoptic Climatological Analysis of Winter Visibility Trends in the Mideastern United States. Atmospheric Environment. Part B. Urban Atmosphere, 25, 165-175. https://doi.org/10.1016/0957-1272(91)90052-G
[12]
Zhao, P., Zhang, X., Xu, X. and Zhao, X. (2011) Long-Term Visibility Trends and Characteristics in the Region of Beijing, Tianjin, and Hebei, China. Atmospheric Research, 101, 711-718. https://doi.org/10.1016/j.atmosres.2011.04.019
[13]
Founda, D., Kazadzis, S., Mihalopoulos, N., Gerasopoulos, E., Lianou, M. and Raptis, P.I. (2016) Long-Term Visibility Variation in Athens (1931-2013): A Proxy for Local and Regional Atmospheric Aerosol Loads. Atmospheric Chemistry & Physics, 16, 11219-11236. https://doi.org/10.5194/acp-16-11219-2016
[14]
Mamouri, R.E., Ansmann, A., Nisantzi, A., Solomos, S., Kallos, G. and Hadjimitsis, D.G. (2016) Extreme Dust Storm over the Eastern Mediterranean in September 2015: Satellite, Lidar, and Surface Observations in the Cyprus Region. Atmospheric Chemistry and Physics, 16, 13711-13724.
https://doi.org/10.5194/acp-16-13711-2016
[15]
Ginoux, P., Prospero, J.M., Gill, T.E., Hsu, N.C. and Zhao, M. (2012) Global-Scale Attribution of Anthropogenic and Natural Dust Sources and Their Emission Rates Based on MODIS Deep Blue Aerosol Products. Reviews of Geophysics, 50, 3005.
https://doi.org/10.1029/2012RG000388
[16]
Hsu, N., Gautam, R., Sayer, A., Bettenhausen, C., Li, C., Jeong, M., Tsay, S.C. and Holben, B. (2012) Global and Regional Trends of Aerosol Optical Depth over Land and Ocean Using SeaWiFS Measurements from 1997 to 2010. Atmospheric Chemistry and Physics, 12, 8037-8053. https://doi.org/10.5194/acp-12-8037-2012
[17]
Vandenbussche, S. and De Mazière, M. (2017) African Mineral Dust Sources: A Combined Analysis Based on 3D Dust Aerosols Distributions, Winds and Surface Parameters. Atmospheric Chemistry and Physics Discussions.
https://doi.org/10.5194/acp-2017-809
[18]
Ozer, P., Laghdaf, M.B.O.M., Lemine, S.O.M. and Gassani, J. (2007) Estimation of Air Quality Degradation Due to Saharan Dust at Nouakchott, Mauritania, from Horizontal Visibility Data. Water, Air, and Soil Pollution, 178, 79-87.
https://doi.org/10.1007/s11270-006-9152-8
[19]
Mahowald, N., Ballantine, J., Feddema, J. and Ramankutty, N. (2007) Global Trends in Visibility: Implications for Dust Sources. Atmospheric Chemistry and Physics, 7, 3309-3339. https://doi.org/10.5194/acp-7-3309-2007
[20]
Mbourou, G.N., Bertrand, J. and Nicholson, S. (1997) The Diurnal and Seasonal Cycles of Wind-Borne Dust over Africa North of the Equator. Journal of Applied Meteorology, 36, 868-882.
https://doi.org/10.1175/1520-0450(1997)036<0868:TDASCO>2.0.CO;2
[21]
Cabello, M., Orza, J., Barrero, M., Gordo, E.,Berasaluce, A., Canton, L., Duenas, C., Fernandez, M. and Pérez, M. (2012) Spatial and Temporal Variation of the Impact of an Extreme Saharan Dust Event. Journal of Geophysical Research: Atmospheres, 117, 11204. https://doi.org/10.1029/2012JD017513
[22]
Silue, S., Konare, A., Diedhiou, A., Yoboue, V., Toure, D.E., Assamoi, P., et al. (2013) Spatial and Temporal Variability of Windborne Dust in the Sahel-Sahara Zone in Relation with Synoptic Environment. Scientific Research and Essays, 8, 705-717.
[23]
Baddock, M.C., Strong, C.L., Leys, J., Heidenreich, S., Tews, E. and McTainsh, G.H. (2014) A Visibility and Total Suspended Dust Relationship. Atmospheric Environment, 89, 329-336. https://doi.org/10.1016/j.atmosenv.2014.02.038
[24]
Anjorin, F.O., Utah, E.U. and Buba, D. (2015) An Investigation on Effects of Harmattan Dust (aerosols) on Horizontal Visibility Deterioration over Bauchi, North-Eastern Nigeria. Iranica Journal of Energy and Environment, 6, 92-97.
[25]
Boers, R., van Weele, M., van Meijgaard, E., Savenije, M., Siebesma, A., Bosveld, F. and Stammes, P. (2015) Observations and Projections of Visibility and Aerosol Optical Thickness (1956-2100) in the Netherlands: Impacts of Time-Varying Aerosol Composition and Hygroscopicity. Environmental Research Letters, 10, 015003.
[26]
Madi, D., Kamal, O., Gholamali, M. and Ahmad, D. (2017) Estimation of Relationship Between Aerosol Optical Depth, PM10 and Visibility in Separation of Synoptic Codes, As Important Parameters in Researches Connected to Aerosols; Using Genetic Algorithm in Yazd. International Journal of Environmental Sciences Natural Resources, 7, . https://doi.org/10.19080/IJESNR.2017.07.555720
[27]
Tsai, Y.I., Kuo, S.C., Lee, W.J., Chen, C.L. and Chen, P.T. (2007) Long-Term Visibility Trends in one Highly Urbanized, One Highly Industrialized, and Two Rural areas of Taiwan. Science of the Total Environment, 382, 324-341.
https://doi.org/10.1016/j.scitotenv.2007.04.048
[28]
Engelstaedter, S. and Washington, R. (2007) Atmospheric Controls on the Annual Cycle of North African Dust. Journal of Geophysical Research. Atmospheres, 112, D03103.
[29]
Zender, C.S. and Kwon, E.Y. (2005) Regional Contrasts in Dust Emission Responses to Climate. Journal of Geophysical Research: Atmospheres, 110.
[30]
Evan, A.T., Heidinger, A.K. and Knippertz, P. (2006) Analysis of Winter Dust Activity off the Coast of West Africa Using a New 24-Year over-Water Advanced Very High Resolution Radiometer Satellite Dust Climatology. Journal of Geophysical Research: Atmospheres, 111. https://doi.org/10.1029/2005JD006336
[31]
Fensholt, R., Langanke, T., Rasmussen, K., Reenberg, A., Prince, S.D., Tucker, C., Scholes, R.J., Le, Q.B., Bondeau, A., Eastman, R., et al. (2012) Greenness in Semi-Arid Areas across the Globe 1981-2007—An Earth Observing Satellite Based Analysis of Trends and Drivers. Remote Sensing of Environment, 121, 144-158.
https://doi.org/10.1016/j.rse.2012.01.017
[32]
Evan, A.T. and Mukhopadhyay, S. (2010) African Dust over the Northern Tropical Atlantic: 1955-2008. Journal of Applied Meteorology and Climatology, 49, 2213-2229.
https://doi.org/10.1175/2010JAMC2485.1
[33]
Chiapello, I., Moulin, C. and Prospero, J.M. (2005) Understanding the Long-Term Variability of African Dust Transport across the Atlantic as Recorded in Both Barbados Surface Concentrations and Large-Scale Total Ozone Mapping Spectrometer (TOMS) Optical Thickness. Journal of Geophysical Research: Atmospheres, 110.
https://doi.org/10.1029/2004JD005132
[34]
Lin, M., Tao, J., Chan, C.Y., Cao, J.J., Zhang, Z.S., Zhu, L.H. and Zhang, R.J. (2012) Regression Analyses between Recent Air Quality and Visibility Changes in Megacities at Four Haze Regions in China. Aerosol and Air Quality Research, 12, 1049-1061.
https://doi.org/10.4209/aaqr.2011.11.0220
[35]
Gherboudj, I., Beegum, S.N. and Ghedira, H. (2017) Identifying Natural Dust Source regions over the Middle-East and North-Africa: Estimation of Dust Emission Potential. Earth-Science Reviews, 165, 342-355.
https://doi.org/10.1016/j.earscirev.2016.12.010
[36]
Ginoux, P., Prospero, J.M., Torres, O. and Chin, M. (2004) Long-Term Simulation of Global Dust Distribution with the GOCART Model: Correlation with North Atlantic Oscillation. Environmental Modelling & Software, 19, 113-128.
https://doi.org/10.1016/S1364-8152(03)00114-2
[37]
Schepanski, K. (2018) Transport of Mineral Dust and Its Impact on Climate. Geosciences, 8, 151. https://doi.org/10.3390/geosciences8050151
[38]
N'Datchoh, E., Diallo, I., Konare, A., Silue, S., Ogunjobi, K., Diedhiou, A. and Doumbia, M. (2018) Dust Induced Changes on the West African Summer Monsoon Features. International Journal of Climatology, 38, 452-466.
https://doi.org/10.1002/joc.5187
[39]
Mage, J.O. and Agber, J.N. (2017) Temperature Variability, Intensity of Wind Speed and Visibility during Harmattan in Makurdi Town, Nigeria. Journal of Research in National Development, 15, 198-206. https://www.ajol.info/journals/jorind
[40]
N’Datchoh, E., Konaré, A., Diedhiou, A., Diawara, A., Quansah, E. and Assamoi, P. (2015) Effects of Climate Variability on Savannah Fire Regimes in West Africa. Earth System Dynamics, 6, 161-174. https://doi.org/10.5194/esd-6-161-2015
[41]
Balarabe, M., Abdullah, K. and Nawawi, M. (2015) Long-Term Trend and Seasonal Variability of Horizontal Visibility in Nigerian Troposphere. Atmosphere, 6, 1462-1486.
https://doi.org/10.3390/atmos6101462
[42]
D’Almeida, G.A. (1986) A Model for Saharan Dust Transport. Journal of Climate and Applied Meteorology, 25, 903-916.
https://doi.org/10.1175/1520-0450(1986)025<0903:AMFSDT>2.0.CO;2
[43]
Mohamed, A.B., Frangi, J., Fontan, J. and Druilhet, A. (1992) Spatial and Temporal Variations of Atmospheric Turbidity and Related Parameters in Niger. Journal of Applied Meteorology, 31, 1286-1294.
https://doi.org/10.1175/1520-0450(1992)031<1286:SATVOA>2.0.CO;2
[44]
Camino, C., Cuevas, E., Basart, S., Alonso-Pérez, S., Baldasano, J., Terradellas, E., Marticorena, B., Rodriguez, S. and Berjon, A. (2015) An Empirical Equation to Estimate Mineral Dust Concentrations from Visibility Observations in Northern Africa. Aeolian Research, 16, 55-68. https://doi.org/10.1016/j.aeolia.2014.11.002
[45]
Xiao, S., Wang, Q., Cao, J., Huang, R.J., Chen, W., Han, Y., Xu, H., Liu, S., Zhou, Y., Wang, P., et al. (2014) Long-Term Trends in Visibility and Impacts of Aerosol Composition on Visibility Impairment in Baoji, China. Atmospheric Research, 149, 88-95. https://doi.org/10.1016/j.atmosres.2014.06.006
[46]
Li, Y., Zhao, H. and Wu, Y. (2015) Characteristics of Particulate Matter during Haze and Fog (Pollution) Episodes over Northeast China, Autumn 2013. Aerosol and Air Quality Research, 15, 853-864. https://doi.org/10.4209/aaqr.2014.08.0158
[47]
Huang, L., Chen, M. and Hu, J. (2016) Twelve-Year Trends of PM10 and Visibility in the Hefei Metropolitan Area of China. Advances in Meteorology, 2016, Article ID: 4810796. https://doi.org/10.1155/2016/4810796
[48]
Wu, J., Kurosaki, Y., Shinoda, M. and Kai, K. (2016) Regional Characteristics of Recent Dust Occurrence and Its Controlling Factors in East Asia. SOLA, 12, 187-191.
[49]
Marticorena, B. (2014) Dust Production Mechanisms. In: Knippertz, P. and Stuut, J.B., Eds., Mineral Dust, Springer, Dordrecht, 93-120.
https://doi.org/10.1007/978-94-017-8978-3_5
[50]
Engelstaedter, S., Tegen, I. and Washington, R. (2006) North African Dust Emissions and Transport. Earth-Science Reviews, 79, 73-100.
https://doi.org/10.1016/j.earscirev.2006.06.004
[51]
Zhao, H., Che, H., Ma, Y., Wang, Y., Yang, H., Liu, Y., Wang, Y., Wang, H. and Zhang, X. (2017) The Relationship of PM Variation with Visibility and Mixing-Layer Height under Hazy/Foggy Conditions in the Multi-Cities of Northeast China. International Journal of Environmental Research and Public Health, 14, 471.
https://doi.org/10.3390/ijerph14050471
[52]
Deng, J., Wang, T., Jiang, Z., Xie, M., Zhang, R., Huang, X. and Zhu, J. (2011) Characterization of Visibility and Its Affecting Factors over Nanjing, China. Atmospheric Research, 101, 681-691. https://doi.org/10.1016/j.atmosres.2011.04.016
[53]
Goudie, A.S. and Middleton, N.J. (1992) The Changing Frequency of Dust Storms through Time. Climatic change, 20, 197-225.
https://doi.org/10.1007/BF00139839
[54]
Majewski, G., Rogula-Kozlowska, W., Czechowski, P.O., Badyda, A. and Brandyk, A. (2015) The Impact of Selected Parameters on Visibility: First Results from a Long-Term Campaign in Warsaw, Poland. Atmosphere, 6, 1154-1174.
https://doi.org/10.3390/atmos6081154
[55]
Li, W., Shao, L. and Buseck, P. (2010) Haze Types in Beijing and the Influence of Agricultural Biomass Burning. Atmospheric Chemistry and Physics, 10, 8119-8130.
https://doi.org/10.5194/acp-10-8119-2010
[56]
Nwofor, O.K. (2010) Seasonal Levels of Meteorological Visibility at Port-Harcourt Nigeria and Possible Links to Aerosol Loading and Humidification. The Pacific Journal of Science and Technology, 11, 544.
[57]
Chen, W.N., Chen, Y.C., Kuo, C.Y., Chou, C.H., Cheng, C.H., Huang, C.C., Chang, S.Y., Raman, M.R., Shang, W.L., Chuang, T.Y., et al. (2014) The Real-Time Method of Assessing the Contribution of Individual Sources on Visibility Degradation in Taichung. Science of the Total Environment, 497, 219-228.
https://doi.org/10.1016/j.scitotenv.2014.07.120
[58]
Vautard, R., Yiou, P. and Van Oldenborgh, G.J. (2009) Decline of Fog, Mist and Haze in Europe over the Past 30 Years. Nature Geoscience, 2, 115-119.
https://doi.org/10.1038/ngeo414
[59]
Solomos, S., Abuelgasim, A., Spyrou, C., Binietoglou, I. and Nickovic, S. (2018) Development of a Dynamic Dust-Source Map for NMME-DREAM v1.0 Model Based on MODIS NDVI over the Arabian Peninsula. Geoscientific Model Development Discussions, 12, 979-988. https://doi.org/10.5194/gmd-2018-251
[60]
Kim, D., Chin, M., Bian, H., Tan, Q., Brown, M.E., Zheng, T., You, R., Diehl, T., Ginoux, P. and Kucsera, T. (2013) The Effect of the Dynamic Surface Bareness on Dust Source Function, Emission, and Distribution. Journal of Geophysical Research: Atmospheres, 118, 871-886. https://doi.org/10.1029/2012JD017907
[61]
Vukovic, A., Vujadinovic, M., Pejanovic, G., Andric, J., Kumjian, M., Djurdjevic, V., Dacic, M., Prasad, A., El-Askary, H., Paris, B., et al. (2013) Numerical Simulation of “An American Haboob”. Atmospheric Chemistry & Physics Discussions, 13, 3211-3230.
https://doi.org/10.5194/acpd-13-26175-2013
[62]
Engelstaedter, S., Kohfeld, K., Tegen, I. and Harrison, S. (2003) Controls of Dust Emissions by Vegetation and Topographic Depressions: An Evaluation Using Dust Storm Frequency Data. Geophysical Research Letters, 30.
https://doi.org/10.1029/2002GL016471
[63]
Heumann, B.W., Seaquist, J., Eklundh, L. and Jonsson, P. (2007) AVHRR Derived Phenological Change in the Sahel and Soudan, Africa, 1982-2005. Remote Sensing of Environment, 108, 385-392. https://doi.org/10.1016/j.rse.2006.11.025
[64]
Aili, A., Oanh, N.T.K. and Abuduwaili, J. (2016) Variation Trends of Dust Storms in Relation to Meteorological Conditions and Anthropogenic Impacts in the Northeast Edge of the Taklimakan Desert, China. Open Journal of Air Pollution, 5, 127-143.
https://doi.org/10.4236/ojap.2016.54010
