著者

NGUYEN T. Hanh ISHIJIMA Kentaro SUGAWARA Satoshi HASEBE Fumio

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-056, (Released:2021-05-20)

---

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 CO2- and SF6-derived mean ages. The reliability of the simulated transport field has been verified by the reproducibility of the observed CO2, SF6, and water vapor profiles using the Lagrangian method. The profile of CO2 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 CO2 age above 25 km altitude possibly due to high diffusivity in the transport model. In contrast, the SF6 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 SF6 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 SF6-depleted mesospheric air, leading to overestimation of the mean age.

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 CO₂- and SF₆-derived mean ages. The reliability of the simulated transport field has been verified by the reproducibility of the observed CO₂, SF₆, and water vapor profiles using the Lagrangian method. The profile of CO₂ 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 CO₂ age above 25 km altitude possibly due to high diffusivity in the transport model. In contrast, the SF₆ 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 SF₆ 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 SF₆-depleted mesospheric air, leading to overestimation of the mean age.</p>