HR: 0800h
AN: OS51A-1287    [Abstracts]
TI: Analysis of Seasonal Chlorophyll-a Using An Adjoint Three-Dimensional Ocean Carbon Cycle Model
AU: * Tjiputra, J
EM: jftjiputra@wisc.edu
AF: University of Wisconsin-Madison, Dept. of Atmospheric and Oceanic Sciences 1225 W. Dayton St., Madison, WI 53705 United States
AU: Winguth, A
EM: amwinguth@wisc.edu
AF: University of Wisconsin-Madison, Dept. of Atmospheric and Oceanic Sciences 1225 W. Dayton St., Madison, WI 53705 United States
AU: Polzin, D
EM: dtpolzin@wisc.edu
AF: University of Wisconsin-Madison, Dept. of Atmospheric and Oceanic Sciences 1225 W. Dayton St., Madison, WI 53705 United States
AB: The misfit between numerical ocean model and observations can be reduced using data assimilation. This can be achieved by optimizing the model parameter values using adjoint model. The adjoint model minimizes the model-data misfit by estimating the sensitivity or gradient of the cost function with respect to initial condition, boundary condition, or parameters. The adjoint technique was used to assimilate seasonal chlorophyll-a data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite to a marine biogeochemical model HAMOCC5.1. An Identical Twin Experiment (ITE) was conducted to test the robustness of the model and the non-linearity level of the forward model. The ITE experiment successfully recovered most of the perturbed parameter to their initial values, and identified the most sensitive ecosystem parameters, which contribute significantly to model-data bias. The regional assimilations of SeaWiFS chlorophyll-a data into the model were able to reduce the model-data misfit (i.e. the cost function) significantly. The cost function reduction mostly occurred in the high latitudes (e.g. the model-data misfit in the northern region during summer season was reduced by 54%). On the other hand, the equatorial regions appear to be relatively stable with no strong reduction in cost function. The optimized parameter set is used to forecast the carbon fluxes between marine ecosystem compartments (e.g. Phytoplankton, Zooplankton, Nutrients, Particulate Organic Carbon, and Dissolved Organic Carbon). The a posteriori model run using the regional best-fit parameterization yields approximately 36 PgC/yr of global net primary productions in the euphotic zone.
DE: 4805 Biogeochemical cycles (1615)
DE: 4815 Ecosystems, structure and dynamics
DE: 4842 Modeling
DE: 4255 Numerical modeling
DE: 1640 Remote sensing
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting