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| NIRE Annual Report |
| 1998 |
Concentration Variations of Lower Tropospheric |
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Objectives
To predict the climate of the future, a better understanding of the behavior of greenhouse gases such as CO2 and CH4 is necessary. In this report, the results of the observation of the atmospheric CO2 and CH4 concentrations over the central Pacific Ocean mainly along 175ºE and their interpretation in terms of the atmospheric transport using a 3-D trajectory analysis are shown.
Results
In spring, the concentration decreases southward from the northern mid-latitudes to the southern low latitudes reflecting the CO2 emissions due to respiration of land biosphere and human activities at northern middle and high latitudes, and changes discontinuously near 10ºS.(Fig.1) The CO2 varies largely at latitudes to the north of 30ºN in both seasons, which is positively and negatively correlated to the CH4 concentration in spring and summer, respectively, as shown in Fig. 2. To interpret these variations in terms of air transport, a trajectory analysis was performed. It was found from the result for the concentration change near 10ºS that air converged from the north and the south to this latitudinal zone, where the South Pacific Convergence Zone was located during the observation period in spring and suppressed latitudinal air mixing. As a result, the CO2 concentration was discontinuously changed in this region. From the results of the analysis for the large concentration variations observed at latitudes to the north of 30ºN, it was suggested that exchange of air masses originating over continents and the ocean had seasonally different influences on the CO2 and CH4 concentration variations in this region, as shown in Fig. 3.
