Potential Contribution of Hyperspectral and Polarimetric Remote Sensing for Fire Emission Characterization from the NASA ER-2 Aircraft

Biomass burning (BB) is a significant air pollution source, and BB emissions are composed of a complex mixture of gases and particles that may directly and indirectly affect both air quality and climate. There is a critical need to investigate the potential contribution of new-generation airborne remote sensing techniques for high-resolution, large-scale emissions and smoke plume development characterization in order to provide observational constraints on the dispersion of BB pollutants from landscape fires.

Remote sensing from NASA’s ER-2 high-altitude research aircraft can provide large-scale, high-resolution observations of fire temperature, plume rise, and characteristics of emitted gaseous and particulate pollutants. In particular we focus on observations from the Hyperspectral Thermal Emission Spectrometer (HyTES), recently integrated on the ER-2, that produces a wide-swath thermal infrared (TIR) image with high spectral (256 bands from 7.5 to 12 μm) and spatial resolution (34 m from the altitude of the ER-2), and the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) that acquires multiangular observations over a ±67° along-track range in eight (355, 380, 445, 470, 555, 660, 865, 935 nm) spectral and three (470, 660, and 865 nm) polarimetric bands with 10 m resolution from the ER-2. Using data from recent field campaigns including SEAC⁴RS and IMPACT-PM, we demonstrate how hyperspectral thermal and multi-angle, spectropolarimetric remote sensing imagery can be used to constrain gaseous emissions and particulate composition of smoke.

We demonstrate that AirMSPI is able to quantify plume rise and BC content of smoke, while HyTES is able to quantify the fire temperature, as well as ammonia (NH₃) and methane (CH₄) emissions, even in the presence of smoke particulates. These capabilities are critically needed for constraining joint aerosol-gas emissions from fires, and for determining the impacts of smoke on local and regional air-quality. In order to translate these retrieval capabilities to space, we also investigate historical MISR, TES, AIRS, and IASI satellite observations collocated over different types of wildfires to quantify the relationships between fire emissions of gases, especially NH₃, and primary and secondary aerosol production as a function of combustion type and ambient atmospheric conditions.

Our results highlight the potential benefits of future joint analysis of particulate and gaseous emissions from the same BB plume with the HyTES and AirMSPI instruments flying together on the ER-2 platform, and utility of such collocated observations for improving our understanding of BB aging processes.