- 著者
-
NGUYEN T. Hanh
ISHIJIMA Kentaro
SUGAWARA Satoshi
HASEBE Fumio
- 出版者
- 公益社団法人 日本気象学会
- 雑誌
- 気象集誌. 第2輯 (ISSN:00261165)
- 巻号頁・発行日
- 2021
<p> Stratospheric profiles of the mean age of air estimated from cryogenic air samples acquired during a field campaign over Indonesia, the Coordinated Upper-Troposphere-to-Stratosphere Balloon Experiment in Biak (CUBE/Biak), are investigated by employing the boundary impulse evolving response (BIER) method and Lagrangian backward trajectories, with the aid of an atmospheric general circulation model-based chemistry transport model (ACTM). The ACTM provides realistic meteorological fields at one-hour intervals by nudging toward the European Centre for Medium-Range Weather Forecasts Reanalysis-Interim (ERA-Interim). Since the BIER method is capable of taking unresolved diffusive processes into account, while the Lagrangian method can distinguish the pathways the air parcels took before reaching the sample site, the application of the two methods to the common transport field simulated by the ACTM is useful in assessing the CO<sub>2</sub>- and SF<sub>6</sub>-derived mean ages. The reliability of the simulated transport field has been verified by the reproducibility of the observed CO<sub>2</sub>, SF<sub>6</sub>, and water vapor profiles using the Lagrangian method. The profile of CO<sub>2</sub> age is reproduced reasonably well by the Lagrangian method with a small young bias being consistent with the termination of trajectories in finite length of time, whereas the BIER method overestimates the CO<sub>2</sub> age above 25 km altitude possibly due to high diffusivity in the transport model. In contrast, the SF<sub>6</sub> age is only reproducible in the lower stratosphere, and far exceeds the estimates from the Lagrangian method above 25 km altitude. As air parcels of mesospheric origin are excluded in the Lagrangian age estimation, this discrepancy, together with the fact that the observed SF<sub>6</sub> mole fractions are much lower than the trajectory-derived values in this height region, supports the idea that the stratospheric air samples are mixed with SF<sub>6</sub>-depleted mesospheric air, leading to overestimation of the mean age.</p>