NIES/FRCGC Global Atmospheric Tracer Transport Model: Description, Validation, and Surface Sources and Sinks Inversion

We present description, validation, utilization, and update of the NIES/FRCGC (National Institute for Environmental Studies/Frontier Research Center for Global Change) off-line global atmospheric tracer transport model. The model transport is driven by analyzed meteorological fields and designed to simulate seasonal and diurnal cycles, synoptic variations, and spatial distributions of atmospheric chemical constituents in the tropo- sphere. Tracer transport is simulated with semi-Lagrangian transport algorithm. The vertical mixing by the boundary layer turbulence and penetrative convection are parameterized. We have tested the model performance against observations of radon-222 and SF 6. The long-lived tracer transport properties are also compared to the other models and observations using the simulation of atmospheric-CO2. Our results suggest that the model can produce realistic interhemispheric exchange rate and vertical tracer distributions in lower and mid troposphere. A new version (NIES05) of the transport model has been developed for simulating diurnally varying CO2 con- centrations at much finer horizontal resolution (0.25˚· 0.25˚· 47 level). The high resolution model results show large improvements in match with the observations at a continental site Tsukuba (~50km north-west of Tokyo). The NIES/FRCGC model is adopted to run on Earth Simulator for the purpose of source/sinks inversion of atmospheric-CO 2. We used interannually varying meteorology for the forward simulations of known CO2 fluxes and normalized emissions from 64 divisions of the globe for which CO2 fluxes are determined by inverse mod- eling of atmospheric-CO2. We have discussed the long-term trends and interannual variability in global and regional CO2 fluxes. The results suggest weak increases and reduction in total land/ocean and southern ocean sinks, respectively, for the period of 1982-2004. The estimated land flux variabilities have been explained by accounting for ecosystem response to inter-annual climate variability and forest fires.