Improvement and validation of trace gas retrieval from ACAM aircraft observation

Friday, 19 December 2014
Cheng Liu1, Xiong Liu1, Matthew G Kowalewski2, Scott J Janz3, Gonzalo Gonzalez Abad4, Kenneth E Pickering5, Kelly Chance6 and Lok N Lamsal7, (1)Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)NASA GSFC, Greenbelt, MD, United States, (4)Center for Astrophysics, Cambridge, MA, United States, (5)NASA Goddard Space Flight Cent, Greenbelt, MD, United States, (6)Harvard-Smithsonian, Cambridge, MA, United States, (7)Universities Space Research Association Columbia, Columbia, MD, United States
The ACAM (Airborne Compact Atmospheric Mapper) instrument, flown on board the NASA UC-12 aircraft during the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) campaigns, was designed to provide remote sensing observations of tropospheric and boundary layer pollutants and help understand some of the most important pollutants that directly affect the health of the population.

In this study, slant column densities (SCD) of trace gases (O3, NO2, HCHO) are retrieved from ACAM measurements during the Baltimore-Washington D.C. 2011 campaign by the Basic Optical Absorption Spectroscopy (BOAS) trace gas fitting algorithm using a nonlinear least-squares (NLLS) inversion technique, and then are converted to vertical column densities (VCDs) using the Air Mass Factors (AMF) calculated with the VLIDORT (Vector Linearized Discrete Ordinate Radiative Transfer) model and CMAQ (Community Multi-scale Air Quality) model simulations of trace gas profiles. For surface treatment in the AMF, we use high-resolution MODIS climatological BRDF product (Bidirectional Reflectance Distribution Function) at 470 nm for NO2, and use high-resolution surface albedo derived by combining MODIS and OMI albedo databases for HCHO and O3. We validate ACAM results with coincident ground-based PANDORA, aircraft (P3B) spiral and satellite (OMI) measurements and find out generally good agreement especially for NO2 and O3