Tropospheric NO2 Observations from Airborne Remote Sensors during Discover-AQ: Retrieval and Evaluation

We present a retrieval study for NO₂ from ultraviolet/visible airborne remote sensors that flew during the DISCOVER-AQ field campaigns. These instruments provide observations of NO₂ abundance in the troposphere with the high spatial resolution requirements of next generation geostationary sensors. Our main objectives here are (i) to design and describe a retrieval scheme to derive vertical NO₂ column abundance underneath the aircraft from the airborne spectrometer, (ii) to provide a quantitative assessment of the resulting NO₂ product, and (iii) to analyze NO₂ observations from the ground, aircraft, and satellite for improved understanding of the column-to-surface relationship. The ultimate goal of this work is to derive surface estimates of NO₂ from satellite column observations.