著者

Hidekazu Matsueda Rebecca R. Buchholz Kentaro Ishijima Helen M. Worden Dorit Hammerling Toshinobu Machida

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.205-210, 2019 (Released:2019-09-27)

参考文献数

36

被引用文献数

5

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We analyzed temporal variations of carbon monoxide (CO) in the upper troposphere from 30°N to 30°S observed using instruments aboard commercial airliner flights between Japan and Australia over the period 1993-2016. Here we focused on the CO variations in the Southern Hemisphere (SH) that showed a unique seasonal cycle with an increased CO around October-November every year. The seasonal CO peaks in the SH showed significant interannual variability (IAV), and are notably enhanced in strong El Niño years, especially 1997. The CO enhancements are proportionally associated with CO emissions from Indonesian fires, when compared to the Global Fire Emissions Database (GFED). The IAV of the CO peak anomalies relative to the mean seasonal cycle was assessed by a statistical regression model that uses a combination of multiple climate indices and their interaction terms. We found that over 80% of the CO IAV observed in the upper troposphere could be explained by the model. The largest anomaly in 1997 showed a different CO-climate relationship than the other periods, which could be due to amplification during synchronized climate modes, or include additional influence from other factors such as human activities.

著者

Prabir K. Patra Masayuki Takigawa Shingo Watanabe Naveen Chandra Kentaro Ishijima Yousuke Yamashita

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.91-96, 2018 (Released:2018-07-21)

参考文献数

37

被引用文献数

42

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The accuracy of chemical tracer simulations by atmospheric general circulation model (AGCM)-based chemistry-transport models (ACTMs) depends on the quality of AGCM transport properties, even when the meteorology is nudged towards the reanalysis fields. Here we show that significant improvements in tracer distribution are achieved when hybrid vertical coordinate is implemented in MIROC4.0 AGCM, compared to its predecessors AGCM5.7b based on sigma coordinate. Only explicitly resolved gravity waves are propagated into the stratosphere in MIROC4-ACTM. The MIROC4-ACTM produces “age-of-air” up to about 5 years in the tropical upper stratosphere (∼1 hPa) and about 6 years in the polar middle stratosphere (∼10 hPa), in agreement with observational estimates. Comparisons of MIROC4-ACTM simulation with observed sulphur hexafluoride (SF6) in the troposphere also show remarkable improvements over the AGCM57b-ACTM simulation. MIROC4-ACTM is characterized by weaker convective mass flux and thus older age of air in the tropical troposphere, relative to AGCM57b-ACTM. The role of convective transport on tracer simulations is depicted using vertical cross-sections of 222Rn (radon) distributions. Both the ACTM versions show similar results when compared with 222Rn measurements at remote sites. All aspects of tracer transport in MIROC4-ACTM is promising for inverse modelling of greenhouse gases sources and sinks at reduced bias.

著者

Kentaro Ishijima Masayuki Takigawa Yousuke Yamashita Hisashi Yashiro Chihiro Kodama Masaki Satoh Kazuhiro Tsuboi Hidekazu Matsueda Yosuke Niwa Shigekazu Hirao

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.111-115, 2018 (Released:2018-08-21)

参考文献数

27

被引用文献数

3

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Atmospheric radon-222 (222Rn) variability is analyzed and compared with model simulations made by the Nonhydrostatic Icosahedral Atmospheric Model (NICAM), with three horizontal resolutions (223, 56, and 14 km), in order to understand high 222Rn events predominantly caused by frontal activities. Seasonal variations of event frequency are well reproduced by the model, with correlation coefficients of 0.79 (223 km) to 0.99 (14 km). The three horizontal resolutions can reproduce general features of the observed peak shapes of events in winter, which dominantly reflect the passage of cold fronts that trap dense amounts of 222Rn. Peak height and width are well reproduced by the 56 km and 14 km resolution models, while the 223 km resolution model shows much lower and broader peaks due to insufficient resolution. We also find that simulations of 222Rn and equivalent potential temperature gradient (|∇θe|) during the events show similar horizontal distributions around the 222Rn observation station, suggesting |∇θe| is a useful tool to understand the variability of atmospheric components around fronts. Consequently, model with horizontal resolution of 56 km and 14 km can well simulate spatiotemporal variations of atmospheric components driven by frontal activities, while 223 km resolution is not enough to reproduce them.

著者

Hidekazu Matsueda Rebecca R. Buchholz Kentaro Ishijima Helen M. Worden Dorit Hammerling Toshinobu Machida

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2019-037, (Released:2019-09-06)

被引用文献数

5

---

We analyzed temporal variations of carbon monoxide (CO) in the upper troposphere from 30°N to 30°S observed using instruments aboard commercial airliner flights between Japan and Australia over the period 1993-2016. Here we focused on the CO variations in the Southern Hemisphere (SH) that showed a unique seasonal cycle with an increased CO around October-November every year. The seasonal CO peaks in the SH showed significant interannual variability (IAV), and are notably enhanced in strong El Niño years, especially 1997. The CO enhancements are proportionally associated with CO emissions from Indonesian fires, when compared to the Global Fire Emissions Database (GFED). The IAV of the CO peak anomalies relative to the mean seasonal cycle was assessed by a statistical regression model that uses a combination of multiple climate indices and their interaction terms. We found that over 80% of the CO IAV observed in the upper troposphere could be explained by the model. The largest anomaly in 1997 showed a different CO-climate relationship than the other periods, which could be due to amplification during synchronized climate modes, or include additional influence from other factors such as human activities.