Simultaneous characterization of wildfire smoke and surface properties
with imaging spectroscopy during the FIREX-AQ field campaign
Abstract
We introduce and evaluate an approach for the simultaneous retrieval of
aerosol and surface properties from Airborne Visible/Infrared Imaging
Spectrometer Classic (AVIRIS-C) data collected during wildfires. The
joint National Aeronautics and Space Administration/National Oceanic and
Atmospheric Administration (NASA/NOAA) Fire Influence on Regional to
Global Environments and Air Quality (FIREX-AQ) field campaign took place
in August 2019, and involved two aircraft and coordinated ground-based
observations. The AVIRIS-C instrument acquired data from onboard NASA’s
high altitude ER-2 research aircraft, coincident in space and time with
aerosol observations obtained from the Aerosol Robotic Network (AERONET)
DRAGON mobile platform in the smoke plume downwind of the Williams Flats
Fire in northern Washington in August, 2019. Observations in this smoke
plume were used to assess the capacity of optimal-estimation based
retrievals to simultaneously estimate aerosol optical depth (AOD) and
surface reflectance from Visible Shortwave Infrared (VSWIR) imaging
spectroscopy. Radiative transfer modeling of the sensitivities in
spectral information collected over smoke reveal the potential capacity
of high spectral resolution retrievals to distinguish between sulfate
and smoke aerosol models, as well as sensitivity to the aerosol size
distribution. Comparison with ground-based AERONET observations
demonstrates that AVIRIS-C retrievals of AOD compare favorably with
direct sun AOD measurements. Our analyses suggest that spectral
information collected from the full VSWIR spectral interval, not just
the shortest wavelengths, enables accurate retrievals. We use this
approach to continuously map both aerosols and surface reflectance at
high spatial resolution across heterogeneous terrain, even under
relatively high AOD conditions associated with wildfire smoke.