An Experiment for the Evaluation of the CO2 Budget on a Regional Scale in Hokkaido, JAPAN

The accurate assessment of the global CO2 budget largely depends on the regional observations and estimations of the regional CO2 fluxes. For understanding the CO2 budget on a regional scale, comprehensive experimental research was made at Ishikari plain in Hokkaido, the northernmost island in Japan. The CO2 source data were collected from the public statistical data, and CO2 sink data for typical forests in Hokkaido were based on the results at Tomakomai Flux Research Site and Teshio CC-LaG site. The regional carbon budget was also estimated inversely using an atmospheric transport model with an experimental observation mainly by airplane in the summer and winter of 2003. The estimated regional carbon budgets during the observation period were estimated as -20.7μmol m-2 s-1 within the Ishikari plain in summer, and 18.8μmol m-2 s-1 within the Sapporo urban area in winter. Both the CO2 absorption in summer and the CO2 emission in winter were overestimated as compared with the integrated CO2 sink and source data. The overestimation resulted from complex regional airflow, inadequate distance between the aerial observation lines and large-scale CO2 source, and the problem in temporal and spatial division of CO2 inventory.