Articles | Volume 9, issue 6
Research article
23 Jun 2016
Research article |  | 23 Jun 2016

Nitrogen dioxide observations from the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument: Retrieval algorithm and measurements during DISCOVER-AQ Texas 2013

Caroline R. Nowlan, Xiong Liu, James W. Leitch, Kelly Chance, Gonzalo González Abad, Cheng Liu, Peter Zoogman, Joshua Cole, Thomas Delker, William Good, Frank Murcray, Lyle Ruppert, Daniel Soo, Melanie B. Follette-Cook, Scott J. Janz, Matthew G. Kowalewski, Christopher P. Loughner, Kenneth E. Pickering, Jay R. Herman, Melinda R. Beaver, Russell W. Long, James J. Szykman, Laura M. Judd, Paul Kelley, Winston T. Luke, Xinrong Ren, and Jassim A. Al-Saadi

Abstract. The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument is a test bed for upcoming air quality satellite instruments that will measure backscattered ultraviolet, visible and near-infrared light from geostationary orbit. GeoTASO flew on the NASA Falcon aircraft in its first intensive field measurement campaign during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) Earth Venture Mission over Houston, Texas, in September 2013. Measurements of backscattered solar radiation between 420 and 465 nm collected on 4 days during the campaign are used to determine slant column amounts of NO2 at 250 m  ×  250 m spatial resolution with a fitting precision of 2.2 × 1015 moleculescm−2. These slant columns are converted to tropospheric NO2 vertical columns using a radiative transfer model and trace gas profiles from the Community Multiscale Air Quality (CMAQ) model. Total column NO2 from GeoTASO is well correlated with ground-based Pandora observations (r = 0.90 on the most polluted and cloud-free day of measurements and r = 0.74 overall), with GeoTASO NO2 slightly higher for the most polluted observations. Surface NO2 mixing ratios inferred from GeoTASO using the CMAQ model show good correlation with NO2 measured in situ at the surface during the campaign (r = 0.85). NO2 slant columns from GeoTASO also agree well with preliminary retrievals from the GEO-CAPE Airborne Simulator (GCAS) which flew on the NASA King Air B200 (r = 0.81, slope = 0.91). Enhanced NO2 is resolvable over areas of traffic NOx emissions and near individual petrochemical facilities.

Short summary
The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) instrument is a remote sensing airborne instrument developed in support of future air quality satellite missions that will operate from geostationary orbit. GeoTASO flew in its first intensive field campaign during the DISCOVER-AQ 2013 Earth Venture Mission over Houston, Texas. This paper introduces the instrument and data analysis, and presents GeoTASO's first observations of NO2 at 250 m x 250 m spatial resolution.