HR: 1340h
AN: B33A-0230    [Abstracts]
TI: Seasonal Variation Of Atmospheric CO2 And Carbon Flux From Biosphere Simulated By A Global Coupled Model
AU: * Iguchi, T
EM: iguchi@dpac.dpri.kyoto-u.ac.jp
AF: Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, 611-0011 Japan
AU: Kida, H
EM: kida@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake cho, Kyoto, 606-8502 Japan
AU: Kazaoka, R
EM: kazaoka@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake cho, Kyoto, 606-8502 Japan
AB: To investigate contribution of the biosphere to atmospheric CO2, a simulation was implemented using a global transport model coupled with a biosphere model. The transport model, which was developed by Iguchi and Kida, divides the atmosphere into grid boxes and calculates fluxes between boxes. So it surely conserves total mass of tracers. Sim-CYCLE, the biosphere model developed by Ito and Oikawa, calculates carbon dynamics within the plant and soil of each grid area. In the coupled model, carbon absorption by photosynthesis and emission by respiration and decomposition calculated by Sim-CYCLE are summed up to surface CO2 fluxes of the transport model. Oppositely, CO2 distribution calculated by the transport model is input to Sim-CYCLE. Both models need input data of the atmosphere or soil. In the simulation, 1990 ECMWF/TOGA data set was used for the transport model, and 1990 NCEP/NCAR re-analysis data set was used for Sim-CYCLE. Also NASA/GISS carbon exchange data set was used as carbon flux from fossil fuel consumption, land use change, and ocean. Result of the simulation was compared with CO2 distribution interpolated from 1990 WMO/WDCGG monthly observation data set. Annual and zonal mean CO2 values calculated in the simulation become higher than those observed. Global and annual carbon absorption by the biosphere calculated by Sim-CYCLE was 1.24GtC. Monthly and zonal mean computed CO2 distributions showed seasonal variation that is similar to observation from winter to summer, but not from summer to winter. This result requires the biosphere model more precise reproduction of leaf falling. Seasonal variations of computed and observed CO2 at observation sites were also compared. At most of the sites, the month of the minimum CO2 computed is later than that observed. As concerns seasonal variation of carbon flux from the biosphere, result of the simulation and NASA/GISS carbon flux data set of vegetation were compared. Computed flux by Sim-CYCLE showed longer absorption period on high latitudes in Northern Hemisphere than NASA/GISS data. As mentioned above, this may be because leaf fall is too late and photosynthesis period of vegetation is too long on these latitudes. On low latitudes in South Hemisphere, phase of seasonal variation of carbon flux computed by Sim-CYCLE looks opposite to that of NASA/GISS data. One of the primal reasons is thought to be that area of tropical deciduous forest is too small in this model, and another is that Sim-CYCLE showed seasonal variation of carbon flux from tropical rain forest that is emitting in summer and absorbing in winter. The latter seasonal variation may be true of real evergreen vegetation.
DE: 4806 Carbon cycling
DE: 0315 Biosphere/atmosphere interactions
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting