also cannot be neglected. Daytime mean CH 4 concentrations from the Siberian tower sites were generally higher than CH 4 values reported at NOAA coastal sites in the same latitudinal zone, and the difference in concentrations between two sets of sites was reproduced with a coupled Eulerian-Lagrangian transport model. Simulations of emissions from different CH 4 sources suggested that the major contributor to variation switched from wetlands during summer to fossil fuel during winter.
Abstract. Pollution events extracted from the in situ observations of atmospheric CO 2 and O 2 mixing ratios at Hateruma Island (HAT, 24 • N, 124 • E) during the period from October 2006 and December 2008 are examined. The air mass origins for the pollution events are categorized by using back trajectory analysis, and the oxidative ratios (OR = −O 2 :CO 2 molar exchange ratio) for selected pollution events are calculated. We find that there is a significant difference in the average oxidative ratios between events from China (OR = 1.14 ± 0.12, n = 25) and Japan/Korea (OR = 1.37 ± 0.15, n = 16). These values are in a good agreement with the national average oxidative ratios for the emissions from fossil fuel burning and cement production (FFBC) in China (OR FFBC = 1.11 ± 0.03) and Korea/Japan (OR FFBC = 1.36 ± 0.02). Compared with the observation, simulations of the atmospheric O 2 and CO 2 mixing ratios using Lagrangian particle dispersion models do a good job in reconstructing the average oxidative ratio of the pollution events originating in China but tend to underestimate for events originating in Japan/Korea. A sensitivity test suggests that the simulated atmospheric oxidative ratios at HAT are especially sensitive to changes in Chinese fuel mix.
Abstract. This study assesses the advantages of using a coupled atmospheric-tracer transport model, comprising a global Eulerian model and a global Lagrangian particle dispersion model, to improve the reproducibility of tracer-gas variations affected by the near-field surface emissions and transport around observation sites. The ability to resolve variability in atmospheric composition on an hourly time-scale and a spatial scale of several kilometers would be beneficial for analyzing data from continuous ground-based monitoring and from upcoming space-based observations. The coupled model yields an increase in the horizontal resolution of transport and fluxes, and has been tested in regional-scale studies of atmospheric chemistry. By applying the Lagrangian component to the global domain, we extend this approach to the global scale, thereby enabling computationally efficient global inverse modeling and data assimilation. To validate the coupled model, we compare model-simulated CO 2 concentrations with continuous observations at three sites: two operated by the National Oceanic and Atmospheric Administration, USA, and one operated by the National Institute for Environmental Studies, Japan. As the goal of this study is limited to introducing the new modeling approach, we selected a transport simulation at these three sites to demonstrate how the model may perform at various geographical areas. The coupled model provides improved agreement between modeled and observed CO 2 concentrations in comparison to the Eulerian model. In an area where variability in CO 2 concentration is dominated by a fossil fuel signal, the correlation coefficient between modeled and observed concentrations increases by between 0.05 to 0.1 from the original values of 0.5-0.6 achieved with the Eulerian model.
In-situ observations of atmospheric CO2 and O2 concentrations at Hateruma Island (HAT, 24° N, 124° E) often show synoptic scale pollution events when air masses are transported from East Asian source regions. We calculate the regression slopes (-ΔO2/ΔCO2 molar ratios) of the correlation plots between O2 and CO2 for selected pollution events observed between October 2006 and December 2008. The observed -ΔO2/ΔCO2 ratios vary from 1.0 to 1.7. Categorizing the air mass origins for the pollution events by using back trajectory analysis, we find that there is a significant difference in the average -ΔO2/ΔCO2 ratios between events from China (1.14±0.12, n = 25) and Japan/Korea (1.37±0.15, n = 16). These values are comparable to the -O2:CO2 molar exchange ratios, which are estimated from the national fossil fuel inventories from CDIAC. Simulations using a particle dispersion model reveal that the pollution events at HAT are predominantly CO2 emissions from the combustion of fossil fuels in East Asian countries, which is consistent with the above observational results. Although the average value of the model-predicted -ΔO2/ΔCO2 ratios for Japan/Korea origin is underestimated in comparison with the observation, that for China origin agree well with the observation. The sensitivity experiment suggests that the -ΔO2/ΔCO2 ratio at HAT reflects about 90% of the change in the -O2:CO2 exchange ratio for the fossil carbon emissions from China
SecA is an ATP-driven motor for protein translocation in bacteria and plants. Mycobacteria and listeria were recently found to possess two functionally distinct secA genes. In this study, we found that Cyanidioschyzon merolae, a unicellular red alga, possessed two distinct secA-homologous genes; one encoded in the cell nucleus and the other in the plastid genome. We found that the plastid-encoded SecA homolog showed significant ATPase activity at low temperature, and that the ATPase activity of the nuclear-encoded SecA homolog showed significant activity at high temperature. We propose that the two SecA homologs play different roles in protein translocation.
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