Retrieval of aerosol properties from Airborne Hyper-Angular Rainbow Polarimeter (AirHARP) observations during ACEPOL 2017

• Published in: Atmospheric Measurement Techniques
• Main Authors: A. Puthukkudy, J. V. Martins, L. A. Remer, X. Xu, O. Dubovik, P. Litvinov, B. McBride, S. Burton, H. M. J. Barbosa
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: Environmental engineering; TA170-171; Earthwork. Foundations; TA715-787; Aerosol Robotic Network
• Online Access: https://doi.org/10.5194/amt-13-5207-2020; https://doaj.org/article/7b84d4d45c404b028f5e7a9043318045

Multi-angle polarimetric (MAP) imaging of Earth scenes can be used for the retrieval of microphysical and optical parameters of aerosols and clouds. The Airborne Hyper-Angular Rainbow Polarimeter (AirHARP) is an aircraft MAP instrument with a hyper-angular imaging capability of 60 along-track viewing angles at 670 nm and 20 along-track viewing angles at other wavelengths – 440, 550, and 870 nm – across the full 114 ∘ (94 ∘ ) along-track (cross-track) field of view. Here we report the retrieval of aerosol properties using the Generalized Retrieval of Aerosols and Surface Properties (GRASP) algorithm applied to AirHARP observations collected during the NASA Aerosol Characterization from Polarimeter and Lidar (ACEPOL) campaign in October–November 2017. The retrieved aerosol properties include spherical fraction (SF), aerosol column concentration in multiple size distribution modes, and, with sufficient aerosol loading, complex aerosol refractive index. From these primary retrievals, we derive aerosol optical depth (AOD), Angstrom exponent (AE), and single scattering albedo (SSA). AODs retrieved from AirHARP measurements are compared with the High Spectral Resolution LiDAR-2 (HSRL2) AOD measurements at 532 nm and validated with measurements from collocated Aerosol Robotic NETwork (AERONET) stations. A good agreement with HSRL2 ( ρ =0.940 , |BIAS|=0.062 , mean absolute error (MAE) = 0.122) and AERONET AOD ( <math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">0.010</mn><mo>≤</mo><mtext>MAE</mtext><mo>≤</mo><mn mathvariant="normal">0.015</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="106pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="e4f47a704ee88e38402afe9005d24aa7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-5207-2020-ie00001.svg" width="106pt" height="11pt" ...