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Tracking Nitrogen Oxides Emissions and Nitrate Formation in Biomass Burning Plumes

Year Initially Funded: 2016

Principal Investigator (s): Meredith Hastings, Associate Professor Department of Earth Environmental and Planetary Sciences, Brown University

Co-PI (s): Jack Dibb, Research Associate Professor Institute for the Study of Earth Oceans and Space University of New Hampshire

Topic (s): FIREX

The Fire Influence on Regional and Global Environments Experiment (FIREX) proposes to investigate the influence of fires in the western U.S. on climate and air quality, via an intensive, multi-platform, campaign. As part of this, we propose to track wildfire derived nitrogen oxides (NOx = NO+NO2) and their influence on the oxidative formation of nitrate (particulate NO3¯ and gaseous nitric acid (HNO3), and nitrous acid (HONO)). We will quantify the influence of biomass burning on atmospheric chemistry in the western U.S. using the concentration and isotopic composition of NOx15N), NO3¯ (δ15N, δ18O, D17O), and HONO (δ15N, δ18O). The isotopes of these species offer a new tool for tracking the influence of biomass burning on the formation and chemistry of these important reactive species. Using a recently developed method that captures NOx without any fractionation effects, along with established methods for collecting soluble gases and aerosols, we will target daytime and nighttime air impacted directly by emissions from biomass fires. Our collections will take place via a mobile laboratory allowing us to remain flexible while mission focused. Laboratory studies using our new collection method reveal a direct correlation between the nitrogen isotopic composition (δ15N) of NOX and the δ15N of the biomass (fuel) N. A number of field-based studies link different NOx sources and the δ15-NO3¯ based upon a variety of supportive data (e.g., transport, correlation with other tracers), but none have ever undertaken a comprehensive isotopic characterization of NOx, HONO, and nitrate at the same time, and there are no direct studies of the isotopic composition of reactive N species in biomass burning plumes. We expect that the δ15N of NO3¯ and HONO will have a direct relationship with the δ15N-NOX that will be sensitive to biomass burning emissions and chemistry compared to air influenced by other sources. The oxygen isotopic composition (δ18O, D17O) of HONO and nitrate can track the relative abundances of oxidants (e.g., ozone, OH, RO2) responsible for the formation these reactive N species.

Design, Decisions, and Critical Data for FIREX

Year Initially Funded: 2016

Principal Investigator (s): Robert Yokelson, Research Professor Department of Chemistry, University of Montana

Co-PI (s):

Topic (s): FIREX

Biomass burning (BB) is a globally-distributed year-round phenomenon that is highly variable and complex in chemical composition and intensity. BB is the second largest global producer of CO2 (the main climate forcer), total greenhouse gases, and non-methane organic gases (NMOG), which are precursors for ozone (O3) and organic aerosol (OA). BB is the largest global source of fine primary OA, black carbon (BC, the second largest global climate forcer) and brown carbon (BrC). BB is historically understudied and field sampling of wildfires even in the US just began in 2013, but without comprehensive NMOG measurements. Many mysteries remain about smoke. A large percent of the NMOG emitted are unidentified. Post-emission, a net increase of inorganic aerosol is always measured. OA always evolves, but the net effect can be an increase or small decrease in OA and the factors deciding the outcome are unknown. The accuracy of BC measurements and the effect of organic coatings on BC properties are controversial. It’s now more widely recognized that OA – often previously treated as purely scattering – may absorb light enough to tip the net global effect of BB from cooling to warming. Absorbing OA (i.e. BrC) is produced almost entirely by BB. Few studies have measured BrC emissions and just one measured the BrC lifetime in the field. BrC formation in nighttime smoke due (e.g.) to NO3 chemistry is likely significant, but unstudied, as is nighttime smoke chemistry in general. Smoke impacts on cloud properties are significant, but cloud impacts on smoke thru e.g. enhanced photochemistry, lightning NOX, scavenging, and “in-droplet growth” are almost unstudied.

To address these critical unknowns we will provide both a suite of measurements and assistance with the design and execution of the NOAA FIREX program. We will quantify a critical, foundational suite of ~20-30 trace gases in the Fire Lab stack and night-time smoke using advanced artifact-free optical remote sensing. This includes the major organic and inorganic emissions of both flaming and smoldering and C, H, N, S, O, and Cl species. We will quantify BC and BrC using advanced photoacoustic spectroscopy, which avoids filter-based artifacts, in the fire lab stack and also measure how these species evolve in well-characterized context in smog chambers and nighttime smoke. Our BC and BrC instruments will be part of the first intercomparison of BC measurement techniques carried out in BB aerosol. Yokelson will provide service and timely intelligence to enhance the design and execution of all FIREX components, including the aircraft campaigns. Yokelson’s last 22 years of research includes leading and assisting projects at all scales that: (1) measured BB emissions at the Fire Lab and globally from the ground, air, and space; (2) measured interactions of BB emissions with urban sources, clouds, and biogenics; (3) synthesized lab and field emissions data; (4) advanced photochemical modeling of smoke; (5) developed/deployed new advanced instrumental techniques for smoke characterization, etc. This experience will inform his steering committee service and assistance with all aspects of FIREX.

Studies of Atmospheric Brown Carbon Chemistry in Support of the FIREX Campaign

Year Initially Funded: 2016

Principal Investigator (s): Alexander Laskin, Pacific Northwest National Laboratory

Co-PI (s): Sergey Nizkorodov, Professor Department of Chemistry, University of California, Irvine

Topic (s): FIREX

NOAA’s “Fire Influence on Regional and Global Environments Experiment” (FIREX) is focused on understanding and predicting the impact of North American fires on the atmosphere. Brown Carbon (BrC) is an important type of light-absorbing organic aerosol predominately produced through biomass burning. The mechanisms and rates of its atmospheric transformations that affect its impact on the atmosphere are, however, largely unexplored. This project will examine the chemical composition and atmospheric chemistry of BrC formed in the FIREX studies. Biomass burning is the major source of “primary BrC” emissions while “secondary BrC” is produced through atmospheric multiphase reactions between the gas- and the condensed-phase species present in smoke. BrC is recognized as an important component in the atmosphere that affects climate forcing both directly through absorption of solar and terrestrial radiation and through indirect effects on cloud formation and microphysics. Furthermore, long-range transport and deposition of BrC plays a substantial role in carbon and nitrogen cycling between atmosphere, land, and water.

The existing evidence suggests that even small amounts of strongly absorbing BrC chromophores may have a pronounced effect on the overall optical properties of organic aerosol. Although the chemical composition of BrC is not well-characterized, several classes of compounds have been proposed to contribute to its light absorption properties. Specifically, nitrogen-containing nitroaromatic compounds (e.g. nitrophenols) and reduced nitrogen species (e.g. imidazoles and other N-heterocyclic compounds) have been identified as BrC chromophores. Less is known about the molecular composition of light-absorbing humic-like substances and oligomers produced through condensation reactions. It has been also proposed that supramolecular aggregates and complexes of organic molecules with transition metals may be responsible for the observed optical properties of BrC. However, it is unclear whether typical BrC is composed of a few strong chromophores or is a mixture of a large number of weak chromophores. Furthermore, little is known about the effect of photochemical aging during atmospheric transport of BrC on its light absorption.

The proposed work will characterize the chemical composition of BrC formed in FIREX studies; identify key chromophores, their light-absorbing properties and concentrations; and examine their transformation upon atmospheric aging. This information is critically important to obtaining predictive understanding of the regional (e.g. Western US) and global impact of BrC on the atmosphere. The proposed research will address the following questions aligned with the FIREX objectives: 1) What is the chemical composition, molecular identity and light-absorption properties of BrC chromophores associated with emissions of aerosols from North American fires? 2) What are the chemical transformations of BrC chromophores during atmospheric aging? 3) What is the impact of nitrogen-containing compounds on the optical properties of BrC? 4) What BrC chromophores are common across different emission sources, and what BrC chromophores are source-specific?

Investigating the Nighttime Chemistry of Biomass Burning Emissions

Year Initially Funded: 2016

Principal Investigator (s): Kelley Barsanti, Assistant Professor Department of Chemical & Environmental Engineering, University of California, Riverside

Co-PI (s): Steven Brown, Chemical Sciences Division, NOAA Earth System Research Laboratory
Robert Yokelson, Research Professor Department of Chemistry, University of Montana

Topic (s): FIREX

The nighttime chemistry of biomass burning (BB) plumes has the potential to strongly influence air quality but is completely unknown. As part of the Fire Influence on regional and Global Environments Experiment (FIREX), we propose a multi-investigator collaboration to elucidate the nighttime gas- and particle-phase chemistry in BB plumes. We hypothesize such chemistry is driven by as yet unexplored reactions between nocturnal oxidants (e.g., ozone (O3), nitrate radical (NO3), and dinitrogen pentoxide (N2O5)), with smoldering emissions (e.g., terpenes, oxygenated aromatics, and particulate matter (PM)). To address our hypothesis and provide critical insight into nighttime BB plume chemistry, we will apply the following advanced analytical techniques, in close coordination with other FIREX investigators: 1) two dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) for characterization of gaseous emissions and initial transformation products of non- methane organic compounds (NMOCs); 2) cavity ring-down spectroscopy (CRDS) for NO3, N2O5 and other reactive nitrogen species; 3) open-path Fourier transfer infrared spectroscopy (OP-FTIR) for O3, nitrogen oxides, nitrous acid, ammonia, peroxyalkyl nitrates, light NMOCs, and total terpenes; and 4) photoacoustic extinctiometers (PAX) for brown carbon (BrC) measurements. We will carry out these measurements in a four-phase plan, participating in both laboratory and field studies during FIREX. The set of proposed measurements will provide the most comprehensive emissions inventories and speciation profiles recorded to date, together with observational constraints from laboratory and field studies intended for development of a complete model representation of nighttime BB chemistry.

This proposed research is a key component of the broader effort to understand BB emissions and chemistry envisioned for FIREX. Specific deliverables and outcomes will include: a publicly available database of NMOCs emitted from North American fuels (molecular-level identification and quantification); characterization of nighttime secondary PM production potential (including BrC) in BB plumes; assessment of the influence of nighttime BB plume chemistry on next-day O3 production potential; and recommendations for improved model representation of nighttime chemistry in predictive regional models. Nighttime processes currently are a major uncertainty for models of BB-derived O3 and PM and therefore a limiting factor for accurate predictions of the influences of fire on air quality and climate. The proposed research thus will directly support NOAA’s long term goals in the area of climate adaptation and mitigation (“improved scientific understanding of the changing climate system and its impacts”) and a weather ready nation (“healthy people and communities due to improved air and water quality services”) as articulated in NOAA’s Next Generation Strategic Plan.

Quantification of Gas and Aerosol Characteristics from North American Fires: Emissions, Evolution and Exposure

Year Initially Funded: 2016

Principal Investigator (s): Scott Herndon, Aerodyne Research, Inc.

Co-PI (s):

Ezra Wood, Research Assistant Professor, University of Massachusetts, Amherst

Topic (s): FIREX

Open biomass burning (BB) fires in North America, including wildland fires and agricultural burning, have a significant impact on our nation’s air quality, our citizen’s health, and our overall contribution to global climate forcing. Emission, evolution, and transport of gas-phase species, aerosol, and radical precursors from open fires, with a focus on greenhouse gases, absorbing aerosol (black and brown carbon), and health-related compounds (i.e., EPA criteria pollutants including particulate matter, PM), must be understood in order to project the climate and health impacts of policy decisions about wildfire and land use management onto the relevant local, regional and global scales. Specific outstanding issues include a quantitative radical-based characterization of the photochemistry in BB plumes and its impact on O3 formation and aerosol processing, the impact of nighttime BB emissions and transformations on nighttime air quality and exposure, source (i.e., fuel and combustion conditions) attribution of transported aerosol, and connections between weather and spatial extent of impact.

We propose to deploy the Aerodyne Mobile Laboratory (AML) as part of the NOAA AC4 Program FIREX project to address several knowledge gaps related to the impact of BB on air quality and climate. The AML will participate in two planned studies at the USFS Fire Sciences Laboratory and will be deployed over a wide geographical range to sample BB plumes as part of the field intensive portion of the FIREX project in direct coordination with other ground and aircraft sampling platforms (e.g., the NOAA P3). The AML platform provides a range of sampling strategies, such as rapid deployment to new fires for emissions characterization, fixed site sampling in downwind locations for studying atmospheric evolution of the plumes, stationary sampling as an expanded laboratory space for USFS Fire Sciences Laboratory experiments, and mapping of plume‐affected urban areas for health‐related exposure.

We will deploy multiple new measurement techniques during FIREX onboard the AML, including a chemical amplification technique for measuring peroxy radicals (HO2+RO2), a thermal-dissociation technique for measuring organic nitrates, a negative iodide chemical ionization mass spectrometer (I- CIMS) equipped with Filter Inlet for Gases and AEROsols collector module (FIGAERO) for measuring gas and particle phase compounds, a soot particle aerosol mass spectrometer (SP-AMS) for characterizing the chemical composition of BrC and BC particles (potentially including nitrogen compounds), and several cavity attenuated phase spectroscopy (CAPS)-based single scatter albedo (SSA) monitors for tracking aerosol optical properties (scattering and extinction). We will leverage the mobile capabilities of the AML platform and our state-of-the-art instrumentation suite to focus on four primary objectives: (1) characterize the radical chemistry that contributes to O3 and SOA formation and daytime evolution of the BB plume; (2) track the chemical evolution and spatial extent of nocturnal BB plumes; (3) identify source specific gas- and particle-phase chemical markers in BB plumes; and (4) characterize the initial and evolving chemical, physical, and optical properties of BB aerosol, including BC and BrC particles. These four goals are closely aligned with the goals of the NOAA FIREX project and with NOAA’s long-term climate goal of improved scientific understanding of the changing climate system and its impacts. The matrix of measurements and sampling strategies will provide a rich and unique data set for regional and global climate models and epidemiological models, thus benefiting the general public and scientific community.

Characterizing Oxidized North American Fire Emissions and Their Aqueous/Multiphase Atmospheric Transformations through the FIREX Campaign

Year Initially Funded: 2016

Principal Investigator (s): Barbara Turpin, Professor Environmental Sciences & Engineering University of North Carolina at Chapel Hill

Co-PI (s):

Topic (s): FIREX

Aqueous multiphase chemistry in aging fire plumes can alter the behavior and climate-relevant properties of atmospheric aerosols. Evidence suggests that multiphase chemistry in clouds, fogs and wet aerosols generates organosulfates, imidazoles, polyols and carboxylic acids, which may be processed to form light-absorbing oligomers (brown carbon). Such chemistry is a sink for reactive gases (e.g., isoprene epoxydiols, glyoxal, peroxides, HO2, NH3) and a source of organic aerosol (OA). Although the multiphase chemistry of oxidized fire emissions in pyrocumulus clouds has a high potential to form light-absorbing and –scattering OA, the aqueous chemistry of only a few fire plume organics (phenols and glycolaldehyde) has been studied. Most oxidized organic constituents of fire plumes remain unidentified and their chemistry unexamined. While laboratory and field studies support the formation of brown carbon in reactions involving ammonia (NH3) or amines in wet aerosols and evaporating droplets, the mechanisms of formation during atmospheric processing of fire plumes are largely unknown.

We will measure oxidized gas- and particle-phase emissions, poorly characterized to date, at the Fire Science Laboratory (FSL) as part of FIREX. We will conduct controlled multiphase chemistry experiments at UNC with the complex mixtures of gases collected during FSL burns, to better understand the atmospheric transformation of fire emissions, their aerosol formation and optical properties. We will apply our expertise in aqueous multiphase (heterogeneous) organic chemistry, organic chemical characterization, synthesis, and kinetics to achieve the following specific aims:

(1) Identify oxidized gaseous and particulate organics at the molecular level during planned FSL burns by on- and off-line high-resolution mass spectrometry techniques.

(2) Study SOA formation through cloud processing in pyrocumulus by scrubbing gaseous fire emissions into water (using mist chambers) and conducting aqueous oxidation and droplet evaporation experiments with and without added NH4+/NH3.

(3) Characterize brown carbon from Aims 1 (fresh emissions) and 2 (aged emissions by aqueous-phase chemistry) and determine the chemical composition.

(4) Test hypotheses developed through the work with FSL mixtures by conducting similar experiments with synthetic standards of newly identified single compounds.

Fires in the Western US: Analyzing Emitted Speciated Organic Trace Gases and Aerosols and their Atmospheric Chemical Transformations

Year Initially Funded: 2016

Principal Investigator (s): Allen Goldstein, Professor, Department of Environmental Science, Policy, and Management University of California, Berkeley

Co-PI (s): Nathan Kreisberg, Aerosol Dynamics, Inc.tein

Topic (s): FIREX

Wildfires, particularly in the forested regions of the western U.S., are becoming larger and increasingly more frequent. Understanding local and regional effects on air quality is needed to inform fire management practices and to ensure the health and safety of humans in affected regions. Understanding the global contributions of these wildfires is important to assessing effects on climate. Biomass burning (BB) is the main global source of primary carbonaceous aerosol and the second largest global source of non-methane organic compounds, including volatile and semi-volatile organic compounds that are now understood to be a major contributor to secondary particle formation in the atmosphere. Measured changes in physical properties and chemical composition suggest substantial and rapid chemical aging of BB organic aerosol. While research into the specific trace gases emitted using comprehensive techniques has begun, much work remains especially in the area of characterizing the chemical composition of the semi-volatile and particulate phase of BB organic emissions and their secondary products.

The proposed research aims to elucidate the speciated chemical composition and transformations of intermediate to low-volatility organic compounds emitted from BB. The FIREX study is being planned with a major focus on closing the gap in knowledge by providing unprecedented emission profiling coupled with plume tracking measurements and modeling to predict BBOA levels. Once these air masses are photochemically aged for hours to days, detailed chemical analyses including a full suite of organic aerosol source and product markers are needed to understand mass closure between modeled and measured organic aerosol.

Through powerful chemical separation and identification techniques and by obtaining unprecedented hourly time resolution for chemically speciated measurements of oxygenated intermediate and semi-volatile organic compounds and particle phase organic compounds during FIREX, we expect to make substantial progress in understanding the formation and transformation of wildfire impacts on aerosol loadings in the atmosphere. In-situ hourly gas chromatography mass spectrometry measurements of molecular markers will be made to chemically characterize BB influence and capture diurnal, meteorological and chemical variability. Filter and adsorbent cartridge samples we collect as part of this campaign will be chemically speciated with novel techniques in the laboratory, enabling the discovery of new molecular level markers from both primary and secondary BB sources. Furthermore, through close collaboration with other members of the FIREX Team, our measurements will be used by multiple research groups to address FIREX science questions.

Identifying, Quantifying, and Constraining Uncertainties Associated with Black Carbon Emissions during Open Biomass Burning

Year Initially Funded: 2016

Principal Investigator (s): Andrew May, Assistant Professor, Department of Civil, Environmental, and Geodetic Engineering, The Ohio State University

Co-PI (s): Gavin McMeeking, Handix Scientific, LLC

Topic (s): FIREX

The proposed work will leverage the NOAA-organized Fire Influence on Regional and Global Environments Experiment (FIREX) campaign to study black carbon (BC) emissions from simulated Western US fires. Briefly, this work will provide a comprehensive and systematic inter-comparison of BC instrumentation. Open biomass burning is a major source of atmospheric BC, but large uncertainties exist in BC emission factors (EFBC). These uncertainties can be grouped into two categories: instrument differences and natural variability. Instrument differences are related to various techniques used to measure BC, a generic term that can represents one of three distinct operationally-defined quantities: “equivalent” BC (eBC), “refractory” BC (rBC), and elemental carbon (EC); instrument differences are especially problematic when EFBC representing eBC, rBC, and/or EC are compiled for emission inventories due to potential inconsistencies among techniques. While similar inter-comparison studies have been conducted in the past, it is unclear whether they can resolve EFBC uncertainty; they have either been conducted in controlled environments using simple systems of laboratory-generated BC or if the studies did investigate BC from biomass burning, they are not comprehensive in that they do not provide all three of eBC, rBC, and EC. Natural variability further complicates this uncertainty due to differences in EFBC caused by factors such as modified combustion efficiency (MCE), fuel type, and information related to aerosol chemical composition (e.g., presence of brown carbon (BrC), single-scatter albedo, absorption Ångström exponent).

To overcome these limitations and address the issue of uncertainty in EFBC, we hypothesize that systematic inter-comparisons of various techniques will enable the identification, quantification, and constraint of uncertainties associated with BC emissions from open biomass burning. This will be accomplished by deploying various BC instruments to the Fire Sciences Laboratory (FSL) in Missoula, MT as part of the NOAA FIREX campaign. This will include one in situ method for eBC, four filter-based methods for eBC, one method for rBC, and one method for EC. All will share a common sampling inlet, thus eliminating any systematic sampling biases across the approaches. We will conduct statistical analyses to quantify differences among the various instruments and explore associations between EFBC measurements and factors such as MCE, fuel type, and aerosol chemical composition to improve the understanding of EFBC uncertainties.

The key outcome from this research will be the reconciliation of uncertainties associated with EFBC. Our data analysis and interpretation will provide the means to identify and quantify uncertainties as well as derive conversion factors that can be applied to both historic and future BC datasets to constrain the uncertainties associated with EFBC in emission inventories. Ultimately, this research will facilitate the development of more robust emission inventories and hence, improved predictions by atmospheric chemical transport and climate models.

Influence of Atmospheric Aging on Fire-Derived Carbonaceous Particles: Laboratory Studies and Modeling in Support of FIREX

Year Initially Funded: 2016

Principal Investigator (s): Christopher Cappa, Professor, Department of Civil & Environmental Engineering, University of California, Davis

Co-PI (s): Jesse Kroll, Associate Professor, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology

Topic (s): FIREX

We propose a joint measurement-modeling project that aims to better constrain the climate and air quality impacts of North American wildfires, via the detailed examination of the evolving optical, physical, and chemical properties of fire-derived particulate matter (PM). Such PM includes absorbing species such as black carbon (BC) and brown carbon (BrC), the properties of which are likely to change dramatically in the atmosphere subsequent to emission. Such effects are, however, poorly understood at present, representing major limitations in our ability to predict the amounts, properties, and impacts of wildfire emissions. Thus, we will carry out an extensive series of laboratory experiments involving the detailed measurement of the changes to fire-derived PM with atmospheric oxidation.

Central to this work is the implementation of a new suite of state-of-the-science analytical techniques, providing highly detailed measurements of the chemistry, hygroscopicity, and optics of fine particles in real time. Measurements will be made as a function of oxidant exposure, varied by sampling through a novel oxidation flow reactor. Experiments will be carried out as part of two planned FIREX laboratory intensives, first at the Missoula Fire Sciences Laboratory, and then at the CIRES environmental chamber facility; additional experiments will be carried out in a smaller chamber as well. These experiments will provide precise, multi-wavelength measurements of key optical parameters of fire-derived PM (e.g., absorption and scattering coefficients), as a function of fuel/burn type, oxidant exposure, and relative humidity. This will help address key uncertainties in the contribution of BrC to total light absorption, the extent to which fire-derived PM changes in absorption and scattering over its atmospheric lifetime, and the effect of water uptake on light absorption by BC-containing PM. Results from these experiments will be used to develop a simplified scheme to describe fire-derived carbonaceous aerosol aging. This scheme will be implemented in the coupled GEOS-Chem-RRTMG global chemical transport and radiation model and tested against a suite of airborne observations of smoke over the United States, including measurements made aboard the P3 aircraft during the FIREX intensive. Finally, this model will be used to estimate the climate impacts of U.S. fires, as well as the visibility and human health impacts, and the relative importance of representing carbonaceous aerosol aging in estimating these impacts.

Improving Emissions, Predictions and Impact Assessments of Biomass Burning Smoke and Dynamic Air Quality using FIREX Observations, Ground Networks and Satellite Data

Year Initially Funded: 2016

Principal Investigator (s): Daven Henze, Associate Professor, Environmental Engineering Program, University of Colorado

Co-PI (s):

Pablo Saide, National Center for Atmospheric Research
Gregory R. Carmichael, Professor, Chemical and Biochemical Engineering, University of Iowa
David Streets, Argonne National Laboratory

Topic (s): FIREX

Open biomass burning (including agriculture fires, wildfires, and managed fires) is one of the largest contributors to aerosols and trace gases, and its emissions have a significant influence on air quality, weather, and climate at the local, regional, and global scales. Nevertheless, several challenges have been identified regarding the characterization of these impacts. We thus propose to participate in the FIREX field experiment and complementary research activities to study the following science questions:

  • What are the size distributions and absorptive properties of aerosol emissions from different biomass fuels, and how do these climate-relevant properties evolve to impact actinic flux both directly and via interactions with clouds and other meteorological factors?
  • What is the diurnal and nocturnal magnitude and spatiotemporal variability of aerosol and trace-gas emissions from different types of biomass burning?
  • How can airborne measurements be optimally deployed to address the above questions, given existing observation networks (ground based and satellite), and to what extent do different data sources and inversion techniques reduce uncertainties in smoke emissions estimates?
  • What are the broader impacts of fires on air quality and climate, compared to anthropogenic sources, and how do constraints from FIREX refine these estimates?

These questions will be addressed using new advances in on-line, coupled atmospheric chemistry/meteorological models, and inverse modeling techniques applicable to such coupled models, using current and evolving observation systems to improve: 1) estimates of climate relevant properties (size, absorption) of aerosols from biomass burning; 2) four-dimensional aerosol distributions (from all sources) at regional scales; and 3) estimates of the attribution of impacts to the atmospheric environment due to biomass burning as well as other specific sources. Prior to the field campaign, our team will develop and distribute essential and novel emissions inventories containing wavelength dependent light absorption properties of primary organic aerosols emitted from various fuel-type and combustion sources, size-resolved emissions factors for primary burning aerosols, and updates to anthropogenic emissions of aerosols and trace gases. These emissions, and associated model updates, will be evaluated through comparisons to measurements from additional field campaigns. During the FIREX field campaign, we will provide forecasting tools for flight planning using in-field emissions inversions and modeling experiments to determine which flight tracks would yield the greatest constraints for emissions inversions. In post-mission analysis additional techniques to constrain biomass burning emissions and carbon/nitrogen budgets will be undertaken, including application of satellite products (e.g., from CrIS and TROPOMI), analysis of co-emitted species (e.g., CO, NOX, NH3), and alternative bottom-up and top-down approaches to quantifying fires and their emissions.

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