A comparison of in-situ aircraft measurements of carbon dioxide to GOSAT data measured over Railroad Valley playa, Nevada, USA

Abstract. In this paper we report vertical profiles of CO₂ measured with a cavity ring-down spectrometer (CRDS, Picarro, Inc., 2301-m) on a research aircraft from near ground level to 8 km above mean sea level (a.m.s.l.). The airborne platform employed in this study is an Alpha Jet aircraft operated from NASA Ames Research Center. Flights were undertaken to Railroad Valley, Nevada, USA, to coincide with overpasses of the Greenhouse Gases Observing Satellite (GOSAT). Ground based CO₂ was simultaneously measured using CRDS, also at the time and location of the airborne and satellite measurements. Results of three GOSAT coordinated aircraft profiles and ground based measurements in June 2011 are presented and discussed in this paper. The accuracy of the CO₂ measurements has been determined based upon laboratory calibrations (WMO traceable standard) and pressure/temperature flight simulations in a test chamber. The 2-σ error bars for the CO₂ data presented here are ± 0.4 ppm. Our column CO₂ measurements, which include about 85% of the tropospheric mass, are extrapolated, using two different techniques, to include the remainder of the tropospheric and stratospheric CO₂. The data are then analyzed using the ACOS (Atmospheric CO₂ observations from space; JPL algorithm used to analyze XCO₂ from GOSAT data) averaging kernels. ACOS version 2.9 is used to interpret the GOSAT data in a collaborative effort between JPL and the GOSAT team. Column averaged CO₂, XCO₂, measured by GOSAT and analyzed from our data ranged from 388.1 to 390.5 ppm. Values of XCO₂ determined from our Alpha Jet measurements and from the GOSAT on three overflight days agree within 1 ppm or better (<0.3%).