The importance of plume rise on the concentrations and atmospheric impacts of biomass burning aerosol

Walter, Carolin; Freitas, Saulo R.; Kottmeier, C.; Kraut, Isabel; Rieger, Daniel; Vogel, H.; Vogel, Bernhard

doi:10.5194/acp-16-9201-2016

Cited by 34 publications

(21 citation statements)

References 77 publications

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“…7a. Given its long atmospheric lifetime (Wang and Prinn, 1999), CO can be used as an inert tracer to ac- count for the effects of dilution. A line of regression therefore indicates the source strengths and deviation from this line arise from changes in the organic aerosol due to photolytic effects, secondary organic aerosol (SOA) enhancements, wet removal or dry deposition.…”

Section: Observationsmentioning

confidence: 99%

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

et al. 2019

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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.

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Section: Observationsmentioning

confidence: 99%

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

et al. 2019

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“…For example, uncertainties in cloud predictions affect vertical transport of aerosols and trace gases within clouds [e.g., Barth et al ., ], wet removal [e.g., Croft et al ., ; Wang et al ., ], and photochemical processes below and above clouds [e.g., Liu et al ., ]. In the cloud‐free environment, uncertainties in simulated boundary layer depth and turbulent mixing affect aerosol and precursor concentrations as well as chemical production rates and uncertainties in simulated temperature profiles that affect the buoyancy and injection height of biomass burning plumes [e.g., Walter et al ., ]. There are also limited comprehensive sets of in situ measurements of aerosol microphysical and optical properties aloft needed to evaluate models, compared to the amount of data collected at the surface.…”

Section: Introductionmentioning

confidence: 99%

Model representations of aerosol layers transported from North America over the Atlantic Ocean during the Two‐Column Aerosol Project

et al. 2016

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The ability of the Weather Research and Forecasting model with chemistry (WRF‐Chem) version 3.7 and the Community Atmosphere Model version 5.3 (CAM5) in simulating profiles of aerosol properties is quantified using extensive in situ and remote sensing measurements from the Two‐Column Aerosol Project (TCAP) conducted during July of 2012. TCAP was supported by the U.S. Department of Energy's Atmospheric Radiation Measurement program and was designed to obtain observations within two atmospheric columns; one fixed over Cape Cod, Massachusetts, and the other several hundred kilometers over the ocean. The performance is quantified using most of the available aircraft and surface measurements during July, and 2 days are examined in more detail to identify the processes responsible for the observed aerosol layers. The higher‐resolution WRF‐Chem model produced more aerosol mass in the free troposphere than the coarser‐resolution CAM5 model so that the fraction of aerosol optical thickness above the residual layer from WRF‐Chem was more consistent with lidar measurements. We found that the free troposphere layers are likely due to mean vertical motions associated with synoptic‐scale convergence that lifts aerosols from the boundary layer. The vertical displacement and the time period associated with upward transport in the troposphere depend on the strength of the synoptic system and whether relatively high boundary layer aerosol concentrations are present where convergence occurs. While a parameterization of subgrid scale convective clouds applied in WRF‐Chem modulated the concentrations of aerosols aloft, it did not significantly change the overall altitude and depth of the layers.

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“…For the model runs, EDGAR (Emission Database for Global Atmospheric Research) emission data were used for the anthropogenic emission of gases and aerosols. Natural emissions of biogenic volatile organic compounds, sea salt (Lundgren et al, 2013), mineral dust 130 (Stanelle et al, 2010) and GFAS (Global Fire Assimilation System) emissions from vegetation fires (Kaiser et al, 2012;Walter et al, 2016) are calculated for each model time step. There was a spin-up time of 7 days (29 June to 5 July) and results were observed for 24 hours on 6 July.…”

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confidence: 99%

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

Haslett¹,

Taylor²,

Evans³

et al. 2019

Preprint

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Abstract. Vast quantities of agricultural land in southern and central Africa are burnt between June and September each year, which releases large concentrations of aerosols into the atmosphere. The resulting smoke plumes are carried west over the Atlantic Ocean at altitudes between 2 and 4&#8201;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 boundary layer, over both the ocean and the continent. A median dry aerosol concentration of 6.2&#8201;&#181;g&#8201;m&#8722;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&#8201;&#181;g&#8201;m&#8722;3. This concentration increased to a median of 11.1&#8201;&#181;g&#8201;m&#8722;3 (8.6 to 15.7&#8201;&#181;g&#8201;m&#8722;3) in the immediate outflow from cities. In the continental air mass away from the cities, the median aerosol loading was 7.5&#8201;&#181;g&#8201;m&#8722;3, with an interquartile range of 4.2&#8201;&#181;g&#8201;m&#8722;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&#8201;% to the regional aerosol loading in the boundary layer of southern West Africa during the monsoon season. As a result, the large and growing emissions from the coastal cities are overlaid on an already substantial aerosol background. On a regional scale this renders cloud properties and precipitation less sensitive to future increases in anthropogenic emissions. 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.

show abstract

The importance of plume rise on the concentrations and atmospheric impacts of biomass burning aerosol

Cited by 34 publications

References 77 publications

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

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

Model representations of aerosol layers transported from North America over the Atlantic Ocean during the Two‐Column Aerosol Project

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

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