A stochastic Lagrangian atmospheric transport model to determine global CO₂ sources and sinks - a preliminary discussion

A stochastic Lagrangian model describing the global tropospheric distribution of CO₂ is developed. Available source and sink terms are incorporated in the model. Advection terms are derived from the ECMWF analysed grids. Model output is compared with CO₂ observations obtained from the NOAA Geophysical program. Model estimates of the yearly averaged latitudinal gradient of CO₂ concentration match the observed CO₂ concentrations except over the southern oceans. A biospheric growing season net flux (GSNF) of 6.5 Gt C was found, from model simulations, to explain the observed seasonal cycle in CO₂ concentrations. This value of the GSNF lies within the bounds of previous estimates. The intensity of the biospheric fluxes above 60°N, oceanic fluxes below 45°S and model vertical transport warrant further investigation. -from Author