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

摘要

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 NOsub2/sub at 250?m??×??250?m spatial resolution with a fitting precision of 2.2?×?10sup15/sup?moleculesmspace linebreak="nobreak" width="0.125em"/cmsup?2/sup. These slant columns are converted to tropospheric NOsub2/sub vertical columns using a radiative transfer model and trace gas profiles from the Community Multiscale Air Quality (CMAQ) model. Total column NOsub2/sub from GeoTASO is well correlated with ground-based Pandora observations (ir/i?=?0.90 on the most polluted and cloud-free day of measurements and ir/i?=?0.74 overall), with GeoTASO NOsub2/sub slightly higher for the most polluted observations. Surface NOsub2/sub mixing ratios inferred from GeoTASO using the CMAQ model show good correlation with NOsub2/sub measured in situ at the surface during the campaign (ir/i?=?0.85). NOsub2/sub 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 (ir/i?=?0.81, slope = 0.91). Enhanced NOsub2/sub is resolvable over areas of traffic NOsubix/i/sub emissions and near individual petrochemical facilities.