Reconciling Assumptions in Bottom‐up and Top‐down Approaches for Estimating Aerosol Emission Rates from Wildland Fires using Observations from FIREX‐AQ

Abstract. Top-down approaches to measure total integrated emissions provide verification of bottom-up, temporally-resolved, inventory-based estimations. Aircraft-based measurements of air pollutants from sources in the Canadian oil sands were made in support of the Joint Canada–Alberta Implementation Plan on Oil Sands Monitoring during a summer intensive field campaign between 13 August and 7 September 2013. The measurements contribute to knowledge needed in support of the Joint Canada–Alberta Implementation Plan on Oil Sands Monitoring. This paper describes a Top-down Emission Rate Retrieval Algorithm (TERRA) to determine facility emissions of pollutants, using SO2 and CH4 as examples, based on the aircraft measurements. In this algorithm, the flight path around a facility at multiple heights is mapped to a two-dimensional vertical screen surrounding the facility. The total transport of SO2 and CH4 through this screen is calculated using aircraft wind measurements, and facility emissions are then calculated based on the divergence theorem with estimations of box-top losses, horizontal and vertical turbulent fluxes, surface deposition, and apparent losses due to air densification and chemical reaction. Example calculations for two separate flights are presented. During an upset condition of SO2 emissions on one day, these calculations are within 5% of the industry-reported, bottom-up measurements. During a return to normal operating conditions, the SO2 emissions are within 11% of industry-reported, bottom-up measurements. CH4 emissions calculated with the algorithm are relatively constant within the range of uncertainties. Uncertainty of the emission rates is estimated as 20%, which is primarily due to the unknown SO2 and CH4 mixing ratios near the surface below the lowest flight level.

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Particulate emissions from large North American wildfires estimated using a new top-down method

10.5194/acp-2016-277 ◽

2016 ◽

Cited By ~ 1

Author(s):

T. Nikonovas ◽

P. R. J. North ◽

S. H. Doerr

Keyword(s):

Water Uptake ◽

Optical Thickness ◽

North American ◽

Atmospheric Dispersion ◽

Water Volume ◽

Particulate Emissions ◽

Emission Rates ◽

Night Time ◽

Bottom Up ◽

Aerosol Emission

Abstract. Particulate matter emissions from wildfires affect climate, weather and air quality. However, existing global and regional aerosol emission estimates differ by a factor of up to 4 between different methods. Using a novel approach, we estimate daily total particular matter (TPM) emissions from large wildfires in North American boreal and temper ate regions. Moderate Resolution Imaging Spectroradiometer (MODIS) fire location and aerosol optical thickness (AOT) datasets are coupled with HYSPLIT atmospheric dispersion simulations, attributing identified smoke plumes to sources. Unlike previous approaches, the method (i) combines information from both satellite and AERONET observations to take into account aerosol water uptake and plume specific mass extinction efficiency in converting smoke AOT to TPM, and (ii) does not depend on instantaneous emission rates observed during individual satellite overpasses, which do not sample night-time emissions. The method also allows multiple independent estimates for the same emission period from imagery taken on consecutive days. Repeated fire-emitted AOT estimates for the same emission period over two to three days of plume evolution show increases in plume optical thickness by approximately 10 % for boreal events, and by 40 % for temperate emissions. Inferred median water volume fractions for aged boreal and temperate smoke observations are 0.15 and 0.47 respectively, indicating that the increased AOT is partly explained by aerosol water uptake. TPM emission estimates for boreal events, which predominantly burn during daytime, agree closely with bottom-up Global Fire Emission Database (GFEDv4) and Global Fire Assimilation System (GFASv1.0) inventories, but are lower by approximately 30 % compared to Quick Fire Emission Dataset (QFEDv2) PM2.5, and are higher by approximately a factor of 2 compared to Fire Energetics and Emissions Research (FEERv1) TPM estimates. The discrepancies are larger for temperate fires, which are characterised by lower median FRP values and more significant night-time combustion. The TPM estimates for this study for the biome are lower than QFED PM2.5 by 35 %, and are larger by factors of 2.4, 3.2 and 4 compared with FEER, GFED and GFAS inventories respectively. Large underestimation of TPM emission by bottom-up GFED and GFAS indicates low biases in emission factors or consumed biomass estimates for temperate fires.

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Determining air pollutant emission rates based on mass balance using airborne measurement data over the Alberta oil sands operations

Atmospheric Measurement Techniques ◽

10.5194/amt-8-3745-2015 ◽

2015 ◽

Vol 8 (9) ◽

pp. 3745-3765 ◽

Cited By ~ 40

Author(s):

M. Gordon ◽

S.-M. Li ◽

R. Staebler ◽

A. Darlington ◽

K. Hayden ◽

...

Keyword(s):

Oil Sands ◽

Air Pollutant ◽

Operating Conditions ◽

Pollutant Emission ◽

Retrieval Algorithm ◽

Emission Rates ◽

So2 Emissions ◽

Top Down ◽

Implementation Plan ◽

Bottom Up

Abstract. Top-down approaches to measure total integrated emissions provide verification of bottom-up, temporally resolved, inventory-based estimations. Aircraft-based measurements of air pollutants from sources in the Canadian oil sands were made in support of the Joint Canada–Alberta Implementation Plan for Oil Sands Monitoring during a summer intensive field campaign between 13 August and 7 September 2013. The measurements contribute to knowledge needed in support of the Joint Canada–Alberta Implementation Plan for Oil Sands Monitoring. This paper describes the top-down emission rate retrieval algorithm (TERRA) to determine facility emissions of pollutants, using SO2 and CH4 as examples, based on the aircraft measurements. In this algorithm, the flight path around a facility at multiple heights is mapped to a two-dimensional vertical screen surrounding the facility. The total transport of SO2 and CH4 through this screen is calculated using aircraft wind measurements, and facility emissions are then calculated based on the divergence theorem with estimations of box-top losses, horizontal and vertical turbulent fluxes, surface deposition, and apparent losses due to air densification and chemical reaction. Example calculations for two separate flights are presented. During an upset condition of SO2 emissions on one day, these calculations are within 5 % of the industry-reported, bottom-up measurements. During a return to normal operating conditions, the SO2 emissions are within 11 % of industry-reported, bottom-up measurements. CH4 emissions calculated with the algorithm are relatively constant within the range of uncertainties. Uncertainty of the emission rates is estimated as less than 30 %, which is primarily due to the unknown SO2 and CH4 mixing ratios near the surface below the lowest flight level.

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