Evaluating a 3-D transport model of atmospheric CO2 using ground-based, aircraft, and space-borne data 1School of GeoSciences, University of Edinburgh, King's Buildings, Edinburgh EH9 3JN, UK
2School of the Geosciences and Resources, China University of Geosciences, Beijing, China
3School of Engineering and Applied Sciences, Harvard University, MA 02138, USA
4Atmospheric Chemistry and Dynamics Branch, NASA Goddard Space Flight Center, MD, 20771, USA
5Laboratoire des Sciences du Climat et de l'Environnement, IPSL, CNRS-CEA-UVSQ, Gif sur Yvette, France
6National Institute for Environmental Studies, Tsukuba, Japan
*now at: Department of Ecology, College of Urban and Environmental Science, Peking University, China
Received: 11 May 2010 – Published in Atmos. Chem. Phys. Discuss.: 29 July 2010 Abstract. We evaluate the GEOS-Chem atmospheric transport model (v8-02-01) of CO2 over
2003–2006, driven by GEOS-4 and GEOS-5 meteorology from the NASA Goddard
Global Modeling and Assimilation Office, using surface,
aircraft and space-borne concentration measurements of CO2. We use
an established ensemble Kalman Filter to estimate a posteriori
biospheric+biomass burning (BS + BB) and oceanic (OC) CO2 fluxes from
22 geographical regions, following the TransCom-3 protocol, using
boundary layer CO2 data from a subset of GLOBALVIEW surface sites.
Global annual net BS + BB + OC CO2 fluxes over 2004–2006 for GEOS-4 (GEOS-5) meteorology are
−4.4 ± 0.9 (−4.2 ± 0.9), −3.9 ± 0.9 (−4.5 ± 0.9), and −5.2 ± 0.9
(−4.9 ± 0.9) PgC yr−1, respectively. After taking into account
anthropogenic fossil fuel and bio-fuel emissions,
the global annual net CO2 emissions for 2004–2006 are estimated to
be 4.0 ± 0.9 (4.2 ± 0.9), 4.8 ± 0.9 (4.2 ± 0.9), and 3.8 ± 0.9 (4.1 ± 0.9) PgC yr−1, respectively.
The estimated 3-yr total net emission for GEOS-4 (GEOS-5) meteorology is equal to 12.5 (12.4) PgC,
agreeing with other recent top-down estimates (12–13 PgC). The regional a posteriori fluxes
are broadly consistent in the sign and magnitude of the TransCom-3
study for 1992–1996, but we find larger net sinks over northern and southern continents.
We find large departures
from our a priori over Europe during summer 2003, over temperate
Eurasia during 2004, and over North America during 2005, reflecting an
incomplete description of terrestrial carbon dynamics.
We find GEOS-4 (GEOS-5) a posteriori CO2 concentrations reproduce the
observed surface trend of 1.91–2.43 ppm yr−1 (parts per million per year), depending on latitude,
within 0.15 ppm yr−1 (0.2 ppm yr−1) and the seasonal cycle within 0.2 ppm
(0.2 ppm) at all latitudes.
We find the a posteriori model reproduces
the aircraft vertical profile measurements of CO2 over North
America and Siberia generally within 1.5 ppm in the free and upper
troposphere but can be biased by up to 4–5 ppm in the boundary layer
at the start and end of the growing season.
The model has a small negative bias in the free troposphere CO2 trend
(1.95–2.19 ppm yr−1) compared to AIRS data which has a trend of
2.21–2.63 ppm yr−1 during 2004–2006, consistent with surface data.
Model CO2 concentrations in the upper troposphere, evaluated using
CONTRAIL (Comprehensive Observation Network for TRace gases by
AIrLiner) aircraft measurements, reproduce the magnitude and phase of
the seasonal cycle of CO2 in both hemispheres.
We generally find that the GEOS meteorology reproduces much of the
observed tropospheric CO2 variability, suggesting that
these meteorological fields will help make significant progress in
understanding carbon fluxes as more data become available.
Revised: 11 March 2011 – Accepted: 15 March 2011 – Published: 25 March 2011
Citation: Feng, L., Palmer, P. I., Yang, Y., Yantosca, R. M., Kawa, S. R., Paris, J.-D., Matsueda, H., and Machida, T.: Evaluating a 3-D transport model of atmospheric CO2 using ground-based, aircraft, and space-borne data, Atmos. Chem. Phys., 11, 2789-2803, doi:10.5194/acp-11-2789-2011, 2011.