A Comparison of in-situ Aircraft Measurements of Carbon Dioxide to GOSAT Data Measured Over Railroad Valley Playa, Nevada, USA
Atmospheric Measurement Techniques http://dx.doi.org/10.5194/amtd-5-5641-2012
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%).