We have developed a new data screening technique using an atmospheric transport model and an inverse model. Using this technique, we can use original (not smoothed) observational data for the inversion method. This means that we can enlarge the number of observational data for inversion method and we can estimate carbon dioxide (CO₂) flux history consistently in long period in accordance with the number of the observational sites.  

The CROZEX cruises (November 2004 to January 2005) had the objective to test whether natural iron fertilisation from the Crozet plateau promotes algal blooms. Results from the cruises show that algal blooms created an oceanic CO₂ sink downstream of the Crozet plateau. Vertical advection of water into the mixed layer occurred close to two islands on the plateau. Data from 18 cruises between 1991 and 2002 are used to quantify the seasonal variability of surface pCO₂ and CO₂ air-sea exchange in the region.

To examine vertical distributions of the O₂/N₂ ratio in the stratosphere, air samples were collected using a cryogenic sampler over Sanriku, Japan and Syowa, Antarctica. It was clearly seen that d(O₂/N₂), as well as simultaneously measured d¹⁵N of N₂ and d¹⁸O of O₂, decreased gradually with increasing height in the stratosphere. The observed profiles of stratospheric ï€ d¹⁵N and d¹⁸O were in good agreement with those calculated using a steady state 1-dimensional eddy-diffusion/molecular-diffusion model suggesting that the upward decrease of stratospheric d(O₂/N₂) is caused by O₂ and N₂ molecules fractionated differently by gravity. The stratospheric d(O₂/N₂) corrected for the gravitational separation indicated that the average value at heights above 20-25 km over Sanriku was always higher than the upper tropospheric d(O₂/N₂) value over Japan at the corresponding time, and that it has decreased secularly, as was found in the troposphere.

We present a new version of the global atmospheric tracer transport model driven by analyzed meteorology with diurnally varying mixing in the boundary layer capable of running globally at resolutions up to quarter degree longitude-latitude or higher. The impact of the higher resolution model can be visible in resolving city plumes, airmass boundaries, diurnal cycle, fronts and synoptic scale events often observed in continuous CO₂ monitoring site data.

The effect of rainfall on mass transfer across the air-water interface was investigated through the CO₂ absorption experiments in a turbulent open-channel flow with the free surface. The results show that the rainfall enhances both the turbulent mixing near the free surface on the liquid side and the CO₂ transfer across the interface. The mass transfer coefficient on the liquid side is well correlated by both the mean vertical momentum flux of rainfall, M, and the mean kinetic energy of rain droplets impinging on the unit area of the air-water interface, KEF. However, it was not concluded which of M and KEF is a better parameter for expressing the rainfall effects on the mass transfer. The comparison between the mass transfer coefficient obtained in this study and that obtained in wind-driven turbulence suggests that it is of great importance to consider the rainfall effect on the CO₂ exchange rate between the atmosphere and ocean in precisely estimating the global carbon cycle in a climate model.

The WLEF TV tower in northern Wisconsin is instrumented to take continuous measurements of CO₂ mixing ratio at 6 levels from 11 to 396m. During the spring and summer of 2004 additional CO₂ measurements were deployed on five 76 m communication towers forming a ring around the WLEF tower with a 100-150 km radius.

Measurements of atmospheric O₂/N₂ ratios and CO₂ concentrations can be combined to form the tracer Atmospheric Potential Oxygen (APO), reflecting primarily ocean biogeochemistry and atmospheric circulation. Building on the work of Stephens et al. [1998], we present a new set of APO observations including shipboard collections from the equatorial Pacific. Our data show a smaller interhemispheric gradient than observed in past studies and a substantial APO maximum around the equator. Following a modeling approach developed by Gruber et al. [2001], we compare these observations with APO fields generated by a set of oceanic and atmospheric models. Overall, our model results agree well with observations, but small differences suggest that modeled north-south transport may be too vigorous, air-sea fluxes may be too coarsely resolved in some regions, and seasonal trapping of surface fluxes may be excessive in some model locations.

GOSAT is a satellite to measure the column densities of CO₂ and CH₄ from space globally, and it is scheduled to be launched in 2008. It has a short wavelength infrared (SWIR) Fourier transform spectrometer (FTS) which measures both the ground surface scattered solar light over land and the right reflected light (sun-glint) over ocean. Column densities of CO₂ and CH₄ will be retrieved from the SWIR (i.e. 1.6 µm and 2.0 µm bands) data and the optical path length from oxygen A-band (0.76 µm). A cloud and aerosol sensor composed of three spectral image sensors (0.380, 0.678 and 1.62 µm) is equipped, viewing the wider area than FTS. This is a joint project among Ministry of Environment of Japan (MOE), National Insitutite for Environmental Studies (NIES) and Japan Aerospace Exploration Agency (JAXA).

We carried out airborne campaigns over Europe in order to analyze atmospheric CO₂ variability at the regional scale. Data reveal a higher standard variation in the planetary boundary layer (PBL) against a lower one in the free troposphere (FT), where the air is more well mixed. Ground data generally agree well with airborne measurements when done in the FT, but not in the PBL where they are exposed to local disturbances. Ground stations located in the FT are shown to be representative of a regional scale while PBL observatories provide only locally representative measurements.