Absorbing and Total Aerosols Science Questions

These science questions highlight FIREX goals to quantify both extensive and intensive properties of BB aerosols, and the processes that determine them. These goals will translate to improved understanding of the air-quality impacts of BB aerosol in the United States, and also to global scale climate impacts of BB.

BB Total Aerosol: Science Questions

  1. What is the near and far field direct radiative forcing of primary and secondary total BB aerosol?
    1. What are the primary and secondary emission factors for total aerosol from the fires?
      • How well do remote sensing platforms measure these factors?
    2. What are the extensive impacts of BB aerosol on direct forcing?
      • What are the optical properties of BB total aerosol relevant to radiative impacts?
      • How do they vary with age, water uptake, and altitude?
  2. What are the indirect and semi-direct climate effects of BB aerosol?
    1. How do BB aerosols act as CCN and IN?
      • How do secondary processes affect BB CCN and IN activity?
    2. How do BB aerosols affect the thermal profile of the atmosphere? What are the semi-direct implications of these changes?
  3. What are the health impacts of BB emissions?
    1. How do specific gaseous and aerosol BB emissions affect air quality near the surface? At the mouths of valleys? At long distance from the fires?
  4. How do nighttime processes affect total BB emissions of optical and health-active species?
    1. Nighttime BB processes are poorly constrained, but may result in substantially different BB emissions and injection heights than day-time burning.
      • How do day- and night-time burning emission factors differ for specific fires?
      • Are the influences of nighttime burning on air quality and health for impacted communities different than day-time burns?
      • Are they different for climate relevant species/processes?

Aerosol Light Absorption: Climate Questions

  1. What are the properties of black and brown carbon from North American Fires relevant to climate?
    1. What are the physical and chemical properties of primary BC and BrC?
      • Can these properties be tied to flame parameters? There are still significant uncertainties associated with the various forms of BC and BrC, and the processes that generate them.
    2. What are the optical properties of primary (and young) BB aerosol over the solar spectrum? Relevant intensive properties include single scatter albedo, asymmetry factor and phase function, and angstrom exponents of scattering and absorption.
      • How do the various forms of BC and BrC aerosol contribute, in both absolute and relative senses, to aerosol absorption? These determine whether BB primary emissions will provide net cooling or warming.
    3. What are the injection heights of the primary BB aerosol? Can the injection height be related to the flaming state of the fire, which will affect aerosol composition and radiative properties with other fire parameters?
      • Injection height affects the lifetime, geographic scale, and impacts of the emissions
  2. How do the radiative impacts of black and brown carbon from BB evolve in time?
    1. How does the microphysical state of BC change with plume age due to secondary production and due to photochemical/chemical aging of existing internal mixtures with BC, and how does this affect BC's radiative effects?
    2. How does brown carbon evolve with plume age?
      • Are there secondary sources of Brown carbon? Does primary or secondary brown carbon bleach photochemically? Does primary or secondary brown carbon volatize? How do the scattering properties of primary or secondary BB BrC vary in relationship to its absorption?
      • The mechanisms that determine the evolution of BrC's light absorbing properties are not well understood, and introduce large uncertainties in estimating its climate impact.
  3. How well can we predict BB contributions to direct radiative effects?
    1. Can closure between in-situ and remote measurements from instruments like lidars and sunphotometers be achieved? What factors may prevent improved closure?
    2. How well do regional and global models predict the BB influence on AAOD?
    3. How well do remote sensing networks quantify BB optical impacts in the American Northwest?