著者

Masato Sugi Yohei Yamada Kohei Yoshida Ryo Mizuta Masuo Nakano Chihiro Kodama Masaki Satoh

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.70-74, 2020 (Released:2020-05-01)

参考文献数

22

被引用文献数

31

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In relation to projections of tropical cyclone (TC) frequency in a future warmer climate, there is a debate on whether the global frequency of TC seeds (weak pre-storm vortices) will increase or not. We examined changes in the frequency of TC seeds by occurrence frequency analysis (OFA) of vortex intensity (vorticity or maximum wind speed). We directly counted the number of vortices with various intensities in high resolution global atmospheric model simulations for present and future climates. By using the OFA we showed a clear reduction of the occurrence frequency of TC seeds and relatively weak (category 2 or weaker) TCs in a future warmer climate, with an increase in the frequency of the most intense (category 5) TCs. The results suggest that the OFA is a useful method to estimate the future changes in TC frequency distribution ranging from TC seeds to the most intense TCs.

著者

Masato Sugi Yohei Yamada Kohei Yoshida Ryo Mizuta Masuo Nakano Chihiro Kodama Masaki Satoh

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-012, (Released:2020-03-19)

被引用文献数

31

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In relation to projections of tropical cyclone (TC) frequency in a future warmer climate, there is a debate on whether the global frequency of TC seeds (weak pre-storm vortices) will increase or not. We examined changes in the frequency of TC seeds by occurrence frequency analysis (OFA) of vortex intensity (vorticity or maximum wind speed). We directly counted the number of vortices with various intensities in high resolution global atmospheric model simulations for present and future climates. By using the OFA we showed a clear reduction of the occurrence frequency of TC seeds and relatively weak (category 2 or weaker) TCs in a future warmer climate, with an increase in the frequency of the most intense (category 5) TCs. The results suggest that the OFA is a useful method to estimate the future changes in TC frequency distribution ranging from TC seeds to the most intense TCs.

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

Chihiro Kodama Akira Kuwano-Yoshida Shingo Watanabe Takeshi Doi Hiroki Kashimura Tomoe Nasuno

出版者

Japan Agency for Marine-Earth Science and Technology

雑誌

JAMSTEC Report of Research and Development (ISSN:18801153)

巻号頁・発行日

vol.28, pp.5-34, 2019-04-01 (Released:2019-04-03)

参考文献数

133

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The JAMSTEC Model Intercomparison Project (JMIP) provides a first opportunity to systematically compare multiple global models developed and/or used in JAMSTEC with the aim of moving toward better weather and climate predictions. Here, we evaluate climate simulations obtained from atmospheric models (AFES and MIROC5), atmospheric model with slab ocean (NICAM.12), and fully coupled model (SINTEX-F1 and SINTEX-F2). In these simulations, the sea surface temperature is fixed (for AFES and MIROC5) or nudged (NICAM.12, SINTEX-F1, and SINTEX-F2) to the observed historical one. We focus on the climatology and variability of precipitation and its associated phenomena, including the basic state, the energy budget of the atmosphere, extratropical cyclones, teleconnection, and the Asian monsoon. We further discuss the possible causes of similarities and differences among the five JMIP models. Though some or most of the dynamical and physical packages in the JMIP models have been developed independently, common model biases are found among them. The AFES and MIROC5, and the SINTEX-F1 and SINTEX-F2, show strong similarities. In many respects, NICAM.12 shows unique characteristics, such as the distributions of precipitation, shortwave radiation, and explosive extratropical cyclones and the onset of the Asian summer monsoon. To some extent, the similarities and differences among the JMIP models overlap with those among the Coupled Model Intercomparison Project Phase-5 (CMIP5) models, suggesting that JMIP can be used as a simple and in-depth version of CMIP to investigate the mechanisms of model bias. We suggest that this JMIP framework could be expanded to an intercomparison of weekly-to-seasonal scale weather forecasting; here, more fruitful discussion is expected through intensive collaboration among modeling and observation groups.