著者

Seiji YUKIMOTO Yukimasa ADACHI Masahiro HOSAKA Tomonori SAKAMI Hiromasa YOSHIMURA Mikitoshi HIRABARA Taichu Y. TANAKA Eiki SHINDO Hiroyuki TSUJINO Makoto DEUSHI Ryo MIZUTA Shoukichi YABU Atsushi OBATA Hideyuki NAKANO Tsuyoshi KOSHIRO Tomoaki OSE Akio KITOH

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.90A, pp.23-64, 2012 (Released:2012-06-07)

参考文献数

157

被引用文献数

354 624

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A new global climate model, MRI-CGCM3, has been developed at the Meteorological Research Institute (MRI). This model is an overall upgrade of MRI’s former climate model MRI-CGCM2 series. MRI-CGCM3 is composed of atmosphere-land, aerosol, and ocean-ice models, and is a subset of the MRI’s earth system model MRI-ESM1. Atmospheric component MRI-AGCM3 is interactively coupled with aerosol model to represent direct and indirect effects of aerosols with a new cloud microphysics scheme. Basic experiments for pre-industrial control, historical and climate sensitivity are performed with MRI-CGCM3. In the pre-industrial control experiment, the model exhibits very stable behavior without climatic drifts, at least in the radiation budget, the temperature near the surface and the major indices of ocean circulations. The sea surface temperature (SST) drift is sufficiently small, while there is a 1 W m-2 heating imbalance at the surface. The model’s climate sensitivity is estimated to be 2.11 K with Gregory’s method. The transient climate response (TCR) to 1 % yr-1 increase of carbon dioxide (CO2) concentration is 1.6 K with doubling of CO2 concentration and 4.1 K with quadrupling of CO2 concentration. The simulated present-day mean climate in the historical experiment is evaluated by comparison with observations, including reanalysis. The model reproduces the overall mean climate, including seasonal variation in various aspects in the atmosphere and the oceans. Variability in the simulated climate is also evaluated and is found to be realistic, including El Niño and Southern Oscillation and the Arctic and Antarctic oscillations. However, some important issues are identified. The simulated SST indicates generally cold bias in the Northern Hemisphere (NH) and warm bias in the Southern Hemisphere (SH), and the simulated sea ice expands excessively in the North Atlantic in winter. A double ITCZ also appears in the tropical Pacific, particularly in the austral summer.

著者

Seiji Yukimoto Kunihiko Kodera Rémi Thiéblemont

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.53-58, 2017 (Released:2017-04-04)

参考文献数

29

被引用文献数

8

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A delayed response of the winter North Atlantic oscillation (NAO) to the 11-year solar cycle has been observed and modeled in recent studies. However, the mechanisms creating this 2-4-year delay to the solar cycle have still not been well-understood. This study examines the effects of the 11-year solar cycle and the resulting modulation in the strength of the winter stratospheric polar vortex. A coupled atmosphere–ocean general circulation model is used to simulate these effects by introducing a mechanistic forcing in the stratosphere. The intensified stratospheric polar vortex is shown to induce positive and negative ocean temperature anomalies in the North Atlantic Ocean. The positive ocean temperature anomaly migrated northward and was amplified when it approached an oceanic frontal zone approximately 3 years after the forcing became maximum. This delayed ocean response is similar to that observed. The result of this study supports a previous hypothesis that suggests that the 11-year solar cycle signals on the Earth's surface are produced through a downward penetration of the changes in the stratospheric circulation. Furthermore, the spatial structure of the signal is modulated by its interaction with the ocean circulation.

著者

Kazuyo Murazaki Hirotaka Kamahori Chiaki Kobayashi Seiji Yukimoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.88-95, 2021 (Released:2021-05-07)

参考文献数

32

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This study evaluated the effects of sea surface temperature (SST) resolution on dynamically downscaled daily surface air temperature (Tsrf) in the Kanto region during early summer. Two downscaling experiments and one additional experiment were conducted using different SST datasets for the months of June and July over a 10-year period. The results demonstrated that the Tsrf difference in the Kanto region between the high-resolution SST experiment (Run-H) and the low-resolution SST experiment (Run-C) correlates positively with the difference in surrounding SST. The impact of SST difference depends on the wind direction and speed. By comparing the results with observations at meteorological stations, the number of days with warm Tsrf bias in Run-C significantly reduces in Run-H, but the number of days with cold Tsrf bias still remains. These results suggest that SST resolution influences the downscaled Tsrf reproducibility over land, and it is worthwhile to pay attention to coastal SST.

著者

Kunihiko KODERA Nawo EGUCHI Jae N. LEE Yuhji KURODA Seiji YUKIMOTO

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.89, no.3, pp.283-290, 2011-06-25 (Released:2011-06-30)

参考文献数

24

被引用文献数

7 18

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In mid-January 2009, sudden changes in circulation occurred in the tropical troposphere and stratosphere. Convective activity situated over the equatorial Maritime Continent showed an abrupt weakening, whereas that over the South American to African sectors became stronger. Changes also occurred in the latitudinal structure; convective activity in the Northern Hemisphere became weaker, whereas that in the Southern Hemisphere became stronger. The change in convective activity took place in association with a change in tropical circulation, from east–west to north–south type (i.e., from Walker- to Hadley-type circulation). Almost simultaneously with these events in the troposphere, a change in meridional circulation occurred in the stratosphere during a record-breaking stratospheric sudden warming event in January 2009. Stratospheric tropical temperature showed a decrease in response to a strengthening of the hemispherical meridional circulation. In the present study, we show how the stratospheric and tropospheric circulation changes are dynamically coupled.

著者

Seiji YUKIMOTO Hideaki KAWAI Tsuyoshi KOSHIRO Naga OSHIMA Kohei YOSHIDA Shogo URAKAWA Hiroyuki TSUJINO Makoto DEUSHI Taichu TANAKA Masahiro HOSAKA Shokichi YABU Hiromasa YOSHIMURA Eiki SHINDO Ryo MIZUTA Atsushi OBATA Yukimasa ADACHI Masayoshi ISHII

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.97, no.5, pp.931-965, 2019 (Released:2019-09-19)

参考文献数

135

被引用文献数

212 441

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The new Meteorological Research Institute Earth System Model version 2.0 (MRI-ESM2.0) has been developed based on previous models, MRI-CGCM3 and MRI-ESM1, which participated in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). These models underwent numerous improvements meant for highly accurate climate reproducibility. This paper describes model formulation updates and evaluates basic performance of its physical components. The new model has nominal horizontal resolutions of 100 km for atmosphere and ocean components, similar to the previous models. The atmospheric vertical resolution is 80 layers, which is enhanced from the 48 layers of its predecessor. Accumulation of various improvements concerning clouds, such as a new stratocumulus cloud scheme, led to remarkable reduction in errors in shortwave, longwave, and net radiation at the top of the atmosphere. The resulting errors are sufficiently small compared with those in the CMIP5 models. The improved radiation distribution brings the accurate meridional heat transport required for the ocean and contributes to a reduced surface air temperature (SAT) bias. MRI-ESM2.0 displays realistic reproduction of both mean climate and interannual variability. For instance, the stratospheric quasi-biennial oscillation can now be realistically expressed through the enhanced vertical resolution and introduction of non-orographic gravity wave drag parameterization. For the historical experiment, MRI-ESM2.0 reasonably reproduces global SAT change for recent decades; however, cooling in the 1950s through the 1960s and warming afterward are overestimated compared with observations. MRI-ESM2.0 has been improved in many aspects over the previous models, MRI-CGCM3 and MRI-ESM1, and is expected to demonstrate superior performance in many experiments planned for CMIP6.

著者

Kazuo Kurihara Koji Ishihara Hidetaka Sasaki Yukio Fukuyama Hitomi Saitou Izuru Takayabu Kazuyo Murazaki Yasuo Sato Seiji Yukimoto Akira Noda

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.1, pp.97-100, 2005 (Released:2005-09-14)

参考文献数

14

被引用文献数

36 48

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The Meteorological Research Institute (MRI) and the Japan Meteorological Agency (JMA) projected climate change over Japan due to global warming using a high-resolution Regional Climate Model of 20 km mesh size (RCM20) developed in MRI. Projection was made for 2081 to 2100 following a SRES-A2 scenario. Precipitation projected by RCM20 indicated that increased daily precipitation will be seen during the warm season from June to September. Except for this period, the precipitation amount will not change much or will slightly decrease around Japan. The increase during the warm season will be seen only in the western part of Japan. A possible cause of the increase is an El Niño-like SST pattern in the future. Due to the future increased summer SST in the eastern equatorial Pacific, anti-cyclonic circulation to the south of Japan will intensify and will induce a strong water vapor flux along the rim of the anti-cyclonic anomaly. The intensified flux will converge over the western part of Japan and may increase precipitation. Surface air temperature is projected to increase more than 2°C around Japan in January. In summer, the temperature increase will be lower by about 1°C than in winter.