Multiangle, Polarimetric Observations of Absorbing Aerosols from AirMSPI

The role of absorbing aerosols such as smoke and dust in the climate system is of particular interest due their interaction with radiation that changes the heating profile of the atmosphere, which can in turn affect cloud formation and impact air quality. Multi-angle, spectro-polarimetric observations are a promising tool for better characterizing these types of aerosols due, in part, to their sensitivity to layer height, absorption, and particle non-sphericity. In this presentation, we will describe both modeling and observational studies that demonstrate these capabilities.

We use a vector (polarized) radiative transfer code to model the angular distribution of the polarized radiation reflected from layers of aerosol embedded in a Rayleigh scattering atmosphere. At blue and UV wavelengths, the sensitivity of passive observations of scattered radiation to aerosol absorbing properties and layer height comes primarily from Rayleigh scattering contributions originating above and below the absorbing aerosol layer.

The Jet Propulsion Laboratory’s Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) acquires multiangular observations over a ±67° along-track range in eight (355, 380, 445, 470, 555, 660, 865, 935 nm) radiometric and three (470, 660, and 865 nm) polarimetric bands with resolution up to 10 m from the NASA ER-2 high altitude research aircraft. Using data from recent field campaigns, including the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC⁴RS) and the Imaging Assessment and Characterization of Tropospheric Particulate Matter (ImPACT-PM), we demonstrate how multi-angle, spectropolarimetric remote sensing imagery can be used to determine the composition of atmospheric dust and smoke aerosols. For validation, the results from the AirMSPI remote sensing observations are compared with in situ aerosol measurements from sensors on the DC-8 (SEAC⁴RS) and the Navy CIRPAS Twin Otter (ImPACT-PM).