We developed a new method for in situ measurement of air-sea fluxes of multiple volatile organic compounds (VOCs) by combining proton transfer reaction-mass spectrometry (PTR-MS) and gradient flux (GF) technique. The PTR-MS/GF system was first deployed to determine the air-sea flux of VOCs in the open ocean of the western Pacific, in addition to carbon dioxide and water vapor. Each profiling at seven heights from the ocean surface up to 14 m took 7 min. In total, 34 vertical profiles of VOCs in the marine atmosphere just above the ocean surface were obtained. The vertical gradient observed was significant for dimethyl sulfide (DMS) and acetone with the best-fit curves on quasi-logarithmic relationship. The mean fluxes of DMS and acetone were 5.5 ± 1.5 and 2.7 ± 1.3 μmol/m(2)/day, respectively. These fluxes are in general in accordance with those reported by previous expeditions.

A simple empirical model was developed to calculate the carbon fluxes on a regional scale by integrating the observed ground truth data at a black spruce forest in interior Alaska in 2005 and original NOAA/AVHRR data. The satellite-derived variables of normalized difference vegetation index (NDVI) and land surface temperature (LST) were related with measured leaf area index (LAI) and measured CO2 flux (NEE) using a sub-empirical model, CBAT. In order to scale up the observed fluxes, gross primary production (GPP) and ecosystem respiration (Reco) were separately determined using NDVI and LST. The parameters and relationships were determined by applying the observed ground truth data in 2005. Comparing to the observed dataset, the diurnal and seasonal variations were calculated reasonably. The model satisfactorily reproduced Reco as an hourly base, but GPP tended to be an overestimation caused by the eliminated effect of vapor pressure deficit (VPD). The GPP, Reco and NEE over Alaska's black spruce forests were estimated as 2330, 1920 and -410 g CO2 m -2 , respectively, during the growing season in 2005. Seasonal variations of estimated carbon flux distributions reflected heterogeneous ecosystem conditions.

Exchange of dimethyl sulfide (DMS) between the surface ocean and the lower atmosphere was examined by using proton transfer reaction‐mass spectrometry coupled with the gradient flux (PTR‐MS/GF) system. We deployed the PTR‐MS/GF system and observed vertical gradients of atmospheric DMS just above the sea surface in the subtropical and transitional South Pacific Ocean and the subarctic North Pacific Ocean. In total, we obtained 370 in situ profiles, and of these we used 46 data sets to calculate the sea‐to‐air flux of DMS. The DMS flux determined was in the range from 1.9 to 31 μmol m−2 d−1 and increased with wind speed and biological activity, in reasonable accordance with previous observations in the open ocean. The gas transfer velocity of DMS derived from the PTR‐MS/GF measurements was similar to either that of DMS determined by the eddy covariance technique or that of insoluble gases derived from the dual tracer experiments, depending on the observation sites located in different geographic regions. When atmospheric conditions were strongly stable during the daytime in the subtropical ocean, the PTR‐MS/GF observations captured a daytime versus nighttime difference in DMS mixing ratios in the surface air overlying the ocean surface. The difference was mainly due to the sea‐to‐air DMS emissions and stable atmospheric conditions, thus affecting the gradient of DMS. This indicates that the DMS gradient is strongly controlled by diurnal variations in the vertical structure of the lower atmosphere above the ocean surface.

NDVI (Normalized Difference of Vegetation Index) was employed to estimate the carbon budget remotely with satellite data. However, NDVI has some difficulties in application to agricultural crops, boreal forest, and tundra ecosystems. We proposed a new vegetation index GR (greenery ratio) to detect the vegetation change remotely, and we applied it to estimate CO2 budget of Japanese rice paddy with MODIS satellite data. GR was ratio of green (G) to the trichromatic visible bands (R G B) of MODIS, and an empirical GR-CO2 budget model was developed as functions of MODIS-data and observed micrometeorology and fluxes at the rice paddy of Mase-site. The daily PAR (photosynthetically active radiation) was also estimated by MODIS. The parameterized model provided good performance to estimate daily magnitudes and seasonal trends of GPP (gross primary productivity), however, RE (ecosystem respiration) showed a little under-estimation, especially differed in late growing season. In contradiction to the observed CO2 budget, the estimated budgets were 2 greater of GPP and 5 less of RE and 9 greater of NEE (net ecosystem exchange). The large discrepancy in NEE was owing to the poor estimation of RE after drainage. Further study to improve RE estimation was needed.

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