The 2018 fire season in North America as seen by TROPOMI: aerosol layer height intercomparisons and evaluation of model-derived plume heights

Griffin, Debora; Sioris, Christopher E.; Chen, Jack; Dickson, Nolan; Kovachik, Andrew; Graaf, M. de; Nanda, Swadhin; Veefkind, Pepijn; Dammers, Enrico; McLinden, Chris A.; Makar, Paul A.; Akingunola, Ayodeji

doi:10.5194/amt-13-1427-2020

Cited by 24 publications

(28 citation statements)

References 66 publications

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“…The GEM-MACH version used in this study used a 12-bin particle's size distribution and the aerosols are assumed to be homogeneous mixtures within GEM-MACH. Further model details can be found for example in Griffin et al (2020b). The model input fire emissions are estimated based on hotspot location using the Canadian Forest Fire Emission Prediction System (CFFEPS v2, Chen et al (2019)).…”

Section: Gem-machmentioning

confidence: 99%

Biomass burning nitrogen dioxide emissions derived from space with TROPOMI: methodology and validation

Griffin

McLinden

Dammers

et al. 2021

Preprint

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Abstract. Smoke from wildfires is a significant source of air pollution, which can adversely impact air quality and ecosystems downwind. With the recently increasing intensity and severity of wildfires, the threat to air quality is expected to increase. Satellite-derived biomass burning emissions can fill in gaps in the absence of aircraft or ground-based measurement campaigns, and can help improve the on-line calculation of biomass burning emissions as well as the biomass burning emissions inventories that feed air quality models. This study focuses on satellite-derived NOx emissions using the high-spatial resolution TROPOspheric Monitoring Instrument (TROPOMI) NO2 dataset. Advancements and improvements to the satellite based determination of forest fire NOx emissions are discussed, including information on plume height and effects of aerosol scattering on the satellite-retrieved vertical column densities. Two common top-down emission estimation methods, (1) an Exponentially Modified Gaussian (EMG) and (2) a flux method, are applied to synthetic data to determine the accuracy and the sensitivity to different parameters, including wind fields, satellite sampling, noise, lifetime and plume spread. These tests show that emissions can be accurately estimated from single TROPOMI overpasses. The effect of smoke aerosols on TROPOMI NO2 columns (via AMFs) is estimated and these satellite columns and emission estimates are compared to aircraft observations from four different aircraft campaigns measuring biomass burning plumes in 2018 and 2019 in North America. Our results indicate that applying an explicit aerosol correction to the TROPOMI NO2 columns improve the agreement with the aircraft observations (by about 10–25 %). The aircraft- and satellite-derived emissions are in good agreement within the uncertainties. Both top-down emissions methods work well, however, the EMG method seems to output more consistent results and has better agreement with the aircraft-derived emissions. Assuming a Gaussian plume shape for various biomass burning plumes, we estimate an average NOx e-folding time of 2 ± 1 h from TROPOMI observations. Based on chemistry transport model simulations and aircraft observations, the net emissions of NOx are 1.3 to 1.5 times greater than the satellite-derived NO2 emissions. A correction factor of 1.3 to 1.5 should thus be used to infer net NOx emissions from the satellite retrievals of NO2.

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Section: Gem-machmentioning

confidence: 99%

Biomass burning nitrogen dioxide emissions derived from space with TROPOMI: methodology and validation

Griffin

McLinden

Dammers

et al. 2021

Preprint

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“…The forward model parameterises aerosols with a Henyey-Greenstein scattering phase function (Henyey and Greenstein, 1941) with an asymmetry factor of 0.7, a single scattering albedo of 0.95 and a fixed AOT for an aerosol layer parameterised by a single atmospheric layer with a 50 hPa thickness. These assumptions have to be made since very little a priori information about aerosols in a scene is known.…”

Section: Tropomi Alhmentioning

confidence: 99%

“…A significant majority of successful retrievals in these selected scenes are over a dark surface, owing to the bright surface albedo of the Sahara. The reader is referred to Griffin et al (2020) for comparison of the TROPOMI ALH retrievals over land for biomass burning aerosol plumes with the same from several other instruments including CALIOP.…”

Section: Selected Casesmentioning

confidence: 99%

A first comparison of TROPOMI aerosol layer height (ALH) to CALIOP data

et al. 2020

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Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) level-2 aerosol layer height (ALH) product has now been released to the general public. This product is retrieved using TROPOMI's measurements of the oxygen A-band, radiative transfer model (RTM) calculations augmented by neural networks and an iterative optimal estimation technique. The TROPOMI ALH product will deliver ALH estimates over cloud-free scenes over the ocean and land that contain aerosols above a certain threshold of the measured UV aerosol index (UVAI) in the ultraviolet region. This paper provides background for the ALH product and explores its quality by comparing ALH estimates to similar quantities derived from spaceborne lidars observing the same scene. The spaceborne lidar chosen for this study is the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission, which flies in formation with NASA's A-train constellation since 2006 and is a proven source of data for studying ALHs. The influence of the surface and clouds is discussed, and the aspects of the TROPOMI ALH algorithm that will require future development efforts are highlighted. A case-by-case analysis of the data from the four selected cases (mostly around the Saharan region with approximately 800 co-located TROPOMI pixels and CALIOP profiles in June and December 2018) shows that ALHs retrieved from TROPOMI using the operational Sentinel-5 Precursor Level-2 ALH algorithm is lower than CALIOP aerosol extinction heights by approximately 0.5 km. Looking at data beyond these cases, it is clear that there is a significant difference when it comes to retrievals over land, where these differences can easily go over 1 km on average.

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“…Improvements to air-quality model performance metrics have been a focus for research since the 1980s, starting with dispersion model evaluation (Fox, 1981) and the identification of mean bias and normalized mean square error as potentially useful metrics to complement the Pearson correlation coefficient (Hanna, 1988). More recently, the Pearson correlation coefficient has been noted as being capable of producing high values for relatively poor model results (Krause et al, 2005), as well as being unable to distinguish systematic model underestimation (Yu et al, 2006), unable to provide information on whether data series have a similar magnitude, and capable of providing a false sense of relationship where none exists due to outliers (Duveiller et al, 2016) and clusters of model-observation pairs (Aggarwal and Ranganathan, 2016).…”

Section: Chemistry Evaluationmentioning

confidence: 99%

Forest-fire aerosol–weather feedbacks over western North America using a high-resolution, online coupled air-quality model

et al. 2021

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Abstract. The influence of both anthropogenic and forest-fire emissions, and their subsequent chemical and physical processing, on the accuracy of weather and air-quality forecasts, was studied using a high-resolution, online coupled air-quality model. Simulations were carried out for the period 4 July through 5 August 2019, at 2.5 km horizontal grid cell size, over a 2250×3425 km2 domain covering western Canada and USA, prior to the use of the forecast system as part of the FIREX-AQ ensemble forecast. Several large forest fires took place in the Canadian portion of the domain during the study period. A feature of the implementation was the incorporation of a new online version of the Canadian Forest Fire Emissions Prediction System (CFFEPSv4.0). This inclusion of thermodynamic forest-fire plume-rise calculations directly into the online air-quality model allowed us to simulate the interactions between forest-fire plume development and weather. Incorporating feedbacks resulted in weather forecast performance that exceeded or matched the no-feedback forecast, at greater than 90 % confidence, at most times and heights in the atmosphere. The feedback forecast outperformed the feedback forecast at 35 out of 48 statistical evaluation scores, for PM2.5, NO2, and O3. Relative to the climatological cloud condensation nuclei (CCN) and aerosol optical properties used in the no-feedback simulations, the online coupled model's aerosol indirect and direct effects were shown to result in feedback loops characterized by decreased surface temperatures in regions affected by forest-fire plumes, decreases in stability within the smoke plume, increases in stability further aloft, and increased lower troposphere cloud droplet and raindrop number densities. The aerosol direct and indirect effect reduced oceanic cloud droplet number densities and increased oceanic raindrop number densities, relative to the no-feedback climatological simulation. The aerosol direct and indirect effects were responsible for changes to the near-surface PM2.5 and NO2 concentrations at greater than the 90 % confidence level near the forest fires, with O3 changes remaining below the 90 % confidence level. The simulations show that incorporating aerosol direct and indirect effect feedbacks can significantly improve the accuracy of weather and air-quality forecasts and that forest-fire plume-rise calculations within an online coupled model change the predicted fire plume dispersion and emissions, the latter through changing the meteorology driving fire intensity and fuel consumption.

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The 2018 fire season in North America as seen by TROPOMI: aerosol layer height intercomparisons and evaluation of model-derived plume heights

Cited by 24 publications

References 66 publications

Biomass burning nitrogen dioxide emissions derived from space with TROPOMI: methodology and validation

Biomass burning nitrogen dioxide emissions derived from space with TROPOMI: methodology and validation

A first comparison of TROPOMI aerosol layer height (ALH) to CALIOP data

Forest-fire aerosol–weather feedbacks over western North America using a high-resolution, online coupled air-quality model

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