scholarly journals Vertical distribution and radiative effects of mineral dust and biomass burning aerosol over West Africa during DABEX

2008 ◽  
Vol 113 ◽  
Author(s):  
B. T. Johnson ◽  
B. Heese ◽  
S. A. McFarlane ◽  
P. Chazette ◽  
A. Jones ◽  
...  
Keyword(s):  
West Africa ◽  
Vertical Distribution ◽  
Biomass Burning ◽  
Mineral Dust ◽  
Radiative Effects ◽  
Biomass Burning Aerosol

scholarly journals Variability of aerosol vertical distribution in the Sahel

2010 ◽  
Vol 10 (24) ◽  
pp. 12005-12023 ◽  
Author(s):  
O. Cavalieri ◽  
F. Cairo ◽  
F. Fierli ◽  
G. Di Donfrancesco ◽  
M. Snels ◽  
...  
Keyword(s):  
Optical Properties ◽  
West Africa ◽  
Vertical Distribution ◽  
Southern Hemisphere ◽  
Biomass Burning ◽  
Dry Season ◽  
Aerosol Transport ◽  
Air Masses ◽  
Monsoon Flow ◽  
Biomass Burning Aerosol

Abstract. In this work, we have studied the seasonal and inter-annual variability of the aerosol vertical distribution over Sahelian Africa for the years 2006, 2007 and 2008, characterizing the different kind of aerosols present in the atmosphere in terms of their optical properties observed by ground-based and satellite instruments, and their sources searched for by using trajectory analysis. This study combines data acquired by three ground-based micro lidar systems located in Banizoumbou (Niger), Cinzana (Mali) and M'Bour (Senegal) in the framework of the African Monsoon Multidisciplinary Analysis (AMMA), by the AEROsol RObotic NETwork (AERONET) sun-photometers and by the space-based Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the CALIPSO satellite (Cloud-Aerosol Lidar and Infrared Pathfinder Observations). During winter, the lower levels air masses arriving in the Sahelian region come mainly from North, North-West and from the Atlantic area, while in the upper troposphere air flow generally originates from West Africa, crossing a region characterized by the presence of large biomass burning sources. The sites of Cinzana, Banizoumbou and M'Bour, along a transect of aerosol transport from East to West, are in fact under the influence of tropical biomass burning aerosol emission during the dry season, as revealed by the seasonal pattern of the aerosol optical properties, and by back-trajectory studies. Aerosol produced by biomass burning are observed mainly during the dry season and are confined in the upper layers of the atmosphere. This is particularly evident for 2006, which was characterized by a large presence of biomass burning aerosols in all the three sites. Biomass burning aerosol is also observed during spring when air masses originating from North and East Africa pass over sparse biomass burning sources, and during summer when biomass burning aerosol is transported from the southern part of the continent by the monsoon flow. During summer months, the entire Sahelian region is under the influence of Saharan dust aerosols: the air masses in low levels arrive from West Africa crossing the Sahara desert or from the Southern Hemisphere crossing the Guinea Gulf while in the upper layers air masses still originate from North, North-East. The maximum of the desert dust activity is observed in this period which is characterized by large AOD (above 0.2) and backscattering values. It also corresponds to a maximum in the extension of the aerosol vertical distribution (up to 6 km of altitude). In correspondence, a progressive cleaning up of the lowermost layers of the atmosphere is occurring, especially evident in the Banizoumbou and Cinzana sites. Summer is in fact characterized by extensive and fast convective phenomena. Lidar profiles show at times large dust events loading the atmosphere with aerosol from the ground up to 6 km of altitude. These events are characterized by large total attenuated backscattering values, and alternate with very clear profiles, sometimes separated by only a few hours, indicative of fast removal processes occurring, likely due to intense convective and rain activity. The inter-annual variability in the three year monitoring period is not very significant. An analysis of the aerosol transport pathways, aiming at detecting the main source regions, revealed that air originated from the Saharan desert is present all year long and it is observed in the lower levels of the atmosphere at the beginning and at the end of the year. In the central part of the year it extends upward and the lower levels are less affected by air masses from Saharan desert when the monsoon flow carries air from the Guinea Gulf and the Southern Hemisphere inland.

scholarly journals Impact of aerosols on photovoltaic energy production using a spectrally resolved model chain: A case study for Sub-Sahara West-Africa

2021 ◽  
Author(s):  
Stefanie Meilinger ◽  
Anna Herman-Czezuch ◽  
Armelle Zemo Mekeng ◽  
Nicola Kimiaie ◽  
James Barry
Keyword(s):  
Optical Properties ◽  
West Africa ◽  
Biomass Burning ◽  
Energy Production ◽  
Mineral Dust ◽  
Power Reduction ◽  
Photovoltaic Power ◽  
Spectrally Resolved ◽  
Model Chain

<p>West Africa has a great potential for the application of solar energy systems, as it combines high levels of solar irradiance with a lack of energy production. Southern West Africa is a region with a very high aerosol load. Urbanization, uncontrolled fires, traffic as well as power plants and oil rigs lead to increasing anthropogenic emissions. The naturally circulating north winds bring mineral dust from the Sahel and Sahara and monsoons - sea salt and other oceanic compounds from the south. The EU-funded Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa (DACCIWA) project (2014–2018), dlivered the most complete dataset of the atmosphere over the region to date. In our study, we use in-situ measured optical properties of aerosols from the airborne campaign over the Gulf of Guinea and inland, and from ground measurements in coastal cities.</p> <p>Based on an analysis of the aerosol optical properties form the DACCIWA measurement campaign, the impact of aerosol on PV power is investigated for polycrystalline silicon and amorphous silicon technology using a spectrally resolved model chain. The model considers both spectral effects on global irradiance due to different aerosol properties as well as the spectral response of different PV technologies. First, the contribution of various aerosol types (mineral dust, biomass burning and anthropogenic pollution) derived from a post-project classification is studied. Subsequently, differences between these imaginary aerosol scenarios and a real case during a biomass burning outbreak on July 13, 2016 in Benin are presented. The results show that aerosol emissions due to the biomass outbreak on the day of the case study in Cotonou lead to solar flux losses of up to 55% and photovoltaic power reduction of up to 81% for the polycrystalline cell and 78% for the amorphous cell. The relative impact of aerosols differs depending on aerosol type and concentration, being larger for low solar zenith angles than at noon. For the situation studied in Cotonou, Benin, we are able to show that the inclusion of spectral aspects leads to a significant effect when calculating the PV power. Comparing the effects of aerosols on the photovoltaic power of the two technologies, we find that the amorphous cell suffers a greater reduction in power during the morning and evening hours - when there is more diffuse irradiance - of 36% than the polycrystalline cell (27%). Conversely, in the middle of the day, we observe greater PV power reduction of the polycrystalline cell of 12% compared to the amorphous cell (8%).</p> <p><strong>Acknowledgements:</strong> Funding was provided by  the German BMWi under contract 0350009A and BMBF under contract 03SF0567A-.</p>

scholarly journals The Importance of Plume Rise on the Concentrations and Atmospheric Impacts of Biomass Burning Aerosol

2016 ◽  
Author(s):  
Carolin Walter ◽  
Saulo R. Freitas ◽  
Christoph Kottmeier ◽  
Isabel Kraut ◽  
Daniel Rieger ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Biomass Burning ◽  
Forest Fires ◽  
Atmospheric Stability ◽  
Wave Radiation ◽  
Maximum Height ◽  
Plume Rise ◽  
Biomass Burning Aerosol ◽  
The Vertical Distribution ◽  
Good Agreement

Abstract. We quantified the effects of the plume rise of biomass burning aerosol and gases for the forest fires that occurred in Saskatchewan, Canada, in July 2010. For this purpose, simulations with different assumptions regarding the plume rise and the vertical distribution of the emissions were conducted. Based on comparisons with observations, applying a one-dimensional plume rise model to predict the injection layer in combination with a parametrisation of the vertical distribution of the emissions outperforms approaches in which the plume heights are initially predefined. Approximately 30 % of the fires exceed the height of 2 km and the maximum height is 8.6 km. Using this plume rise model, comparisons with satellite images in the visible spectral range show a very good agreement between the simulated and observed spatial distributions of the biomass burning plume. The simulated AOD with data of an AERONET station is in good agreement with respect to the absolute values and the timing of the maximum. Comparison of the vertical distribution of the biomass burning aerosol with CALIPSO retrievals also showed the best agreement when the plume rise model was applied. We found that down-welling surface short-wave radiation below the forest fire plume is reduced by up to 50 % and that the 2 m temperature is decreased by up to 6 K. In addition, we simulated a strong change in atmospheric stability within the biomass burning plume.

scholarly journals Remote biomass burning dominates southern West African air pollution during the monsoon

2019 ◽  
Vol 19 (24) ◽  
pp. 15217-15234 ◽  
Author(s):  
Sophie L. Haslett ◽  
Jonathan W. Taylor ◽  
Mathew Evans ◽  
Eleanor Morris ◽  
Bernhard Vogel ◽  
...  
Keyword(s):  
Air Pollution ◽  
West Africa ◽  
Atlantic Ocean ◽  
Biomass Burning ◽  
West African ◽  
Small Scale ◽  
High Background ◽  
Accumulation Mode ◽  
Aerosol Loading ◽  
Biomass Burning Aerosol

Abstract. Vast stretches of agricultural land in southern and central Africa are burnt between June and September each year, which releases large quantities of aerosol into the atmosphere. The resulting smoke plumes are carried west over the Atlantic Ocean at altitudes between 2 and 4 km. As only limited observational data in West Africa have existed until now, whether this pollution has an impact at lower altitudes has remained unclear. The Dynamics-aerosol-chemistry-cloud interactions in West Africa (DACCIWA) aircraft campaign took place in southern West Africa during June and July 2016, with the aim of observing gas and aerosol properties in the region in order to assess anthropogenic and other influences on the atmosphere. Results presented here show that a significant mass of aged accumulation mode aerosol was present in the southern West African monsoon layer, over both the ocean and the continent. A median dry aerosol concentration of 6.2 µg m−3 (standard temperature and pressure, STP) was observed over the Atlantic Ocean upwind of the major cities, with an interquartile range from 5.3 to 8.0 µg m−3. This concentration increased to a median of 11.1 µg m−3 (8.6 to 15.7 µg m−3) in the immediate outflow from cities. In the continental air mass away from the cities, the median aerosol loading was 7.5 µg m−3 (5.9 to 10.5 µg m−3). The accumulation mode aerosol population over land displayed similar chemical properties to the upstream population, which implies that upstream aerosol is a significant source of aerosol pollution over the continent. The upstream aerosol is found to have most likely originated from central and southern African biomass burning. This demonstrates that biomass burning plumes are being advected northwards, after being entrained into the monsoon layer over the eastern tropical Atlantic Ocean. It is shown observationally for the first time that they contribute up to 80 % to the regional aerosol loading in the monsoon layer over southern West Africa. Results from the COSMO-ART (Consortium for Small-scale Modeling – Aerosol and Reactive Trace gases) and GEOS-Chem models support this conclusion, showing that observed aerosol concentrations over the northern Atlantic Ocean can only be reproduced when the contribution of transported biomass burning aerosol is taken into account. As a result, the large and growing emissions from the coastal cities are overlaid on an already substantial aerosol background. Simulations using COSMO-ART show that cloud droplet number concentrations can increase by up to 27 % as a result of transported biomass burning aerosol. On a regional scale this renders cloud properties and precipitation less sensitive to future increases in anthropogenic emissions. In addition, such high background loadings will lead to greater pollution exposure for the large and growing population in southern West Africa. These results emphasise the importance of including aerosol from across country borders in the development of air pollution policies and interventions in regions such as West Africa.

scholarly journals Vertical structure of aerosols and water vapor over West Africa during the African monsoon dry season

2009 ◽  
Vol 9 (20) ◽  
pp. 8017-8038 ◽  
Author(s):  
S.-W. Kim ◽  
P. Chazette ◽  
F. Dulac ◽  
J. Sanak ◽  
B. Johnson ◽  
...  
Keyword(s):  
Water Vapor ◽  
West Africa ◽  
Biomass Burning ◽  
Extinction Ratio ◽  
Dry Season ◽  
Water Vapor Transport ◽  
Dust Particles ◽  
Tropospheric Aerosol ◽  
Biomass Burning Aerosol ◽  
High Concentrations

Abstract. We present observations of tropospheric aerosol and water vapor transport over West Africa and the associated meteorological conditions during the AMMA SOP-0 dry season experiment, which was conducted in West Africa in January–February 2006. This study combines data from ultra-light aircraft (ULA)-based lidar, airborne in-situ aerosol and gas measurements, standard meteorological measurements, satellite-based aerosol measurements, airmass trajectories, and radiosonde measurements. At Niamey (13.5° N, 2.2° E) the prevailing surface wind (i.e. Harmattan) was from the northeast bringing dry dusty air from the Sahara desert. High concentrations of mineral dust aerosol were typically observed from the surface to 1.5 or 2 km associated with the Saharan airmasses. At higher altitudes the prevailing wind veered to the south or southeast bringing relatively warm and humid airmasses from the biomass burning regions to the Sahel (<10° N). These elevated layers had high concentrations of biomass burning aerosol and were typically observed between altitudes of 2–5 km. Meteorological analyses show these airmasses were advected upwards over the biomass burning regions through ascent in Inter-Tropical Discontinuity (ITD) zone. Aerosol vertical profiles obtained from the space-based lidar CALIOP onboard CALIPSO during January 2007 also showed the presence of dust particles (particle depolarization (δ)~30%, lidar Ångström exponent (LAE)<0, aerosol backscatter to extinction ratio (BER): 0.026~0.028 sr−1) at low levels (<1.5 km) and biomass burning smoke aerosol (δ<10%, LAE: 0.6~1.1, BER: 0.015~0.018 sr−1) between 2 and 5 km. CALIOP data indicated that these distinct continental dust and biomass burning aerosol layers likely mixed as they advected further south over the tropical Atlantic Ocean, as indicated an intermediate values of δ (10~17%), LAE (0.16~0.18) and BER (0.0021~0.0022 sr−1).

scholarly journals Light absorption properties of aerosols over Southern West Africa

2019 ◽  
Author(s):  
Cyrielle Denjean ◽  
Thierry Bourrianne ◽  
Frederic Burnet ◽  
Marc Mallet ◽  
Nicolas Maury ◽  
...  
Keyword(s):  
Optical Properties ◽  
West Africa ◽  
Biomass Burning ◽  
Aerosol Particles ◽  
Anthropogenic Pollution ◽  
Absorption Properties ◽  
Air Masses ◽  
Carbon Particles ◽  
Biomass Burning Aerosol ◽  
Biomass Burning Particles

Abstract. Southern West Africa (SWA) is an African pollution hotspot but a relatively poorly sampled region of the world. We present an overview of in-situ aerosol optical measurements collected over SWA in June and July 2016 as part as the DACCIWA (Dynamics–Aerosol–Chemistry–Clouds Interactions in West Africa) airborne campaign. The aircraft sampled a wide range of air masses, including anthropogenic pollution plumes emitted from the coastal cities, long-range transported biomass burning plumes from Central and Southern Africa and dust plumes from the Sahara and Sahel region, as well as mixtures of these plumes. The specific objective of this work is to characterize the regional variability of the vertical distribution of aerosol particles and their spectral optical properties (single scattering albedo: SSA, asymmetry parameter, extinction mass efficiency, scattering Ångström exponent and absorption Ångström exponent: AAE). First findings indicate that aerosol optical properties in the planetary boundary layer were dominated by a widespread and persistent biomass burning loading from the Southern Hemisphere. Despite a strong increase of aerosol number concentration in air masses downwind of urban conglomerations, spectral SSA were comparable to the background and showed signatures of the absorption characteristics of biomass burning aerosols. In the free troposphere, moderately to strongly absorbing aerosol layers, dominated by either dust or biomass burning particles, occurred occasionally. In aerosol layers dominated by mineral dust particles, SSA varied from 0.81 to 0.92 at 550 nm depending on the variable proportion of anthropogenic pollution particles externally mixed with the dust. Biomass burning aerosol particles were significantly more light absorbing than those previously measured in other areas (e.g. Amazonia, North America) with SSA ranging from 0.71 to 0.77 at 550 nm. The variability of SSA was mainly controlled by variations in aerosol composition rather than in aerosol size distribution. Correspondingly, values of AAE ranged from 0.9 to 1.1, suggesting that lens-coated black carbon particles were the dominant absorber in the visible range for these biomass burning aerosols. Comparison with literature shows a consistent picture of increasing absorption enhancement of biomass burning aerosol from emission to remote location and underscores that the evolution of SSA occurred a long time after emission. The results presented here build a fundamental basis of knowledge about the aerosol optical properties observed over SWA during the monsoon season and can be used in climate modelling studies and satellite retrievals. In particular and regarding the very high absorbing properties of biomass burning aerosols over SWA, our findings suggest that considering the effect of internal mixing on absorption properties of black carbon particles in climate models should help better assessing the direct and semi-direct radiative effects of biomass burning particles.

Short-wave radiative effects of biomass burning aerosol during SAFARI2000

2004 ◽  
Vol 130 (599) ◽  
pp. 1423-1447 ◽  
Author(s):  
Simon R. Osborne ◽  
James M. Haywood ◽  
Peter N. Francis ◽  
Oleg Dubovik
Keyword(s):  
Biomass Burning ◽  
Short Wave ◽  
Radiative Effects ◽  
Biomass Burning Aerosol

scholarly journals Transport and vertical structure of aerosols and water vapor over West Africa during the African monsoon dry season

2009 ◽  
Vol 9 (1) ◽  
pp. 1831-1871
Author(s):  
S.-W. Kim ◽  
P. Chazette ◽  
F. Dulac ◽  
J. Sanak ◽  
B. Johnson ◽  
...  
Keyword(s):  
Water Vapor ◽  
West Africa ◽  
Biomass Burning ◽  
Surface Wind ◽  
Dry Season ◽  
Water Vapor Transport ◽  
Dust Particles ◽  
Tropospheric Aerosol ◽  
Biomass Burning Aerosol ◽  
High Concentrations

Abstract. We present observations of tropospheric aerosol and water vapor transport over West Africa and the associated meteorological conditions during the AMMA SOP-0 dry season experiment, which was conducted in West Africa in January–February 2006. This study combines data from ultra-light aircraft (ULA)-based lidar, airborne in-situ aerosol and gas measurements, standard meteorological measurements, satellite-based aerosol measurements, airmass trajectories, and radiosonde measurements. At Niamey (13.5° N, 2.2° E) the prevailing surface wind was from the northeast bringing dry dusty air from the Sahara desert. High concentrations of mineral dust aerosol were typically observed from the surface to 1.5 or 2 km associated with the Saharan airmasses. At higher altitudes the prevailing wind veered to the south or southeast bringing relatively warm and humid airmasses from the biomass burning regions to the Sahel (<10° N). These elevated layers had high concentrations of biomass burning aerosol and were typically observed between altitudes of 2–5 km. Meteorological analyses show these airmasses were advected upwards over the biomass burning regions through large-scale ascent, presumably driven by surface heating rather than pyro-convection. Aerosol vertical profiles obtained from the space-based lidar CALIOP onboard CALIPSO during January 2007 also showed the presence of dust particles (depolarization ~30%, color ratio <0) at low levels (<1.5 km) and biomass burning smoke aerosol (depolarization ratio <10%) between 2 and 5 km. CALIOP data indicated that these distinct continental dust and biomass burning aerosol layers likely mixed as they advected further south over the tropical Atlantic Ocean.

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