著者

Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.66-71, 2019 (Released:2019-11-27)

参考文献数

20

被引用文献数

9

---

The predictability of the Heavy Rain Event in July 2018 is examined by forecast experiments with an operational global atmospheric forecast model. Experiments from different initial times show that the overall rainfall distribution at the peak on 6 July can be predicted from 12 UTC, June 30, and later. In the successful forecasts, the track error of Typhoon Prapiroon against the best track is small. In the experiments with longer lead times, by contrast, the Baiu frontal zone has a northwared bias with less precipitation, and Prapiroon hardly develop and migrates westward. Poor track forecasts seem to be related to the limited vertical development of the vortex. Near surface equivalent potential tempeature and Q-vector analysis show that Prapiroon act to intensify the Baiu frontal zone. In conclusion, the correct track forecast is essential for Baiu frontogenesis and the formation of heavy precipitation in western Japan.

著者

Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.15A-012, (Released:2019-10-25)

被引用文献数

9

---

The predictability of the Heavy Rain Event in July 2018 is examined by forecast experiments with an operational global atmospheric forecast model. Experiments from different initial times show that the overall rainfall distribution at the peak on 6 July can be predicted from 12 UTC, June 30, and later. In the successful forecasts, the track error of Typhoon Prapiroon against the best track is small. In the experiments with longer lead times, by contrast, the Baiu frontal zone has a northwared bias with less precipitation, and Prapiroon hardly develop and migrates westward. Poor track forecasts seem to be related to the limited vertical development of the vortex. Near surface equivalent potential tempeature and Q-vector analysis show that Prapiroon act to intensify the Baiu frontal zone. In conclusion, the correct track forecast is essential for Baiu frontogenesis and the formation of heavy precipitation in western Japan.

著者

Masahiro Shiozaki Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.12-16, 2020 (Released:2020-01-31)

参考文献数

11

被引用文献数

1

---

The 2015/16 El Niño is compared with the two previous strongest events, the 1982/83 and 1997/98 El Niño. The 2015/16 winter features a basin warming in the Indian Ocean, a negative sea surface temperature (SST) anomaly shifted to the north in the western Pacific Ocean in addition to a positive SST anomaly shifted to the west in the eastern Pacific Ocean. These SST distributions lead to suppressed convection in the Maritime Continent, and to a weakened Hadley circulation in the western Pacific Ocean. The eastern Asian monsoon in the 2015/16 winter was also weakened due to the dominance of the western Pacific (WP) pattern. On the other hand, the third and fourth centers of action of Pacific/North American (PNA) pattern in the 2015/16 case are obscure. This may be due to weak divergence in the eastern Pacific Ocean.

著者

Saori Nakashita Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17A, no.Special_Edition, pp.33-37, 2021 (Released:2021-04-20)

参考文献数

14

被引用文献数

2

---

The predictability of Typhoon Hagibis in October 2019 is examined with ensemble forecasts from four major operational numerical weather prediction centers. From six to four days before the landfall, the forecast from the Japan Meteorological Agency was the best among the four centers. However, the error increased sharply three days before the landfall. Consistent with the westward track error, a northwestward bias is found in the environmental winds. The ensemble sensitivity analysis for the landing region indicates a large sensitivity to a ridge located to the southeast of the typhoon. The member with the largest track error has perturbations that act to weaken the ridge. A low-pressure disturbance to the southeast of the ridge is found to migrate westward faster than the member with the smallest track error. Therefore, the typhoon is advected westward by the easterlies associated with the low. These results indicate a significant influence of the tropical disturbance on the predictability of Hagibis.

著者

Saori Nakashita Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.17A-006, (Released:2021-03-23)

被引用文献数

2

---

The predictability of Typhoon Hagibis in October 2019 is examined with ensemble forecasts from four major operational numerical weather prediction centers. From six to four days before the landfall, the forecast from the Japan Meteorological Agency was the best among the four centers. However, the error increased sharply three days before the landfall. Consistent with the westward track error, a northwestward bias is found in the environmental winds. The ensemble sensitivity analysis for the landing region indicates a large sensitivity to a ridge located to the southeast of the typhoon. The member with the largest track error has perturbations that act to weaken the ridge. A low-pressure disturbance to the southeast of the ridge is found to migrate westward faster than the member with the smallest track error. Therefore, the typhoon is advected westward by the easterlies associated with the low. These results indicate a significant influence of the tropical disturbance on the predictability of Hagibis.

著者

Miki Hattori Jun Matsumoto Shin-Ya Ogino Takeshi Enomoto Takemasa Miyoshi

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.75-79, 2016 (Released:2016-03-08)

参考文献数

17

被引用文献数

6

---

The impact of additional radiosonde observations during the Vietnam-Philippines Rainfall Experiment 2010 (VPREX2010) was investigated by performing observing system experiments using the local ensemble transform Kalman filter (LETKF) and the atmospheric general circulation model for the Earth Simulator (AFES). During the experimental period from 15 September to 15 October, 2010, a westward-propagating disturbance was developed in the South China Sea and caused heavy rainfall on the east coast of Vietnam and Hainan Island. By assimilating the additional radiosondes, significant increases in wind speed, temperature and specific humidity were detected in the lower troposphere around the disturbance. In addition, the analysis ensemble spread for meridional wind decreased by 5-25% across the Indochina Peninsula, Philippines Sea and western Pacific to the south of Japan. Moreover, winds became stronger around the disturbance due to the additional observations, and the ensemble spread for wind speed became larger. The results show that the disturbance in an early stage of development was not well detected in the South China Sea without the use of additional radiosonde observations. Therefore, it is suggested that continuous and intensive radiosonde observations in Vietnam and the Philippines are essential for the improvement of the objective analysis of such disturbances.

著者

Tetsuro Miyachi Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.140-144, 2021 (Released:2021-08-20)

参考文献数

14

---

Tropical cyclone track forecast experiments were conducted using the National Centers for Environmental Prediction Global Forecast System with the initial conditions from three numerical weather prediction centers, to distinguish between tropical cyclone track forecast errors attributable to the initial state uncertainty and those attributable to the model imperfection. The average position error was reduced by replacing the initial conditions from the European Centre for Medium-range Weather Forecasts. The northward recurvature of Lupit (2009) was not reproduced with initial conditions from the Japan Meteorological Agency. It was consistent with the preceding study, indicating sensitivity to the initial state. The sensitivity to the model and the initial state was obtained for Parma (2009), as opposed to the conclusion of the previous study, where Parma was discovered to be insensitive to the initial state, and the error was assumed to come from the model difference. Insensitivity to the initial vortex structures in the predicted tracks for Parma indicates that the error in the steering flow formed by the environmental field around tropical cyclone contributes to the northward bias.

著者

Tetsuro Miyachi Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-025, (Released:2021-07-20)

---

Tropical cyclone track forecast experiments were conducted using the National Centers for Environmental Prediction Global Forecast System with the initial conditions from three numerical weather prediction centers, to distinguish between tropical cyclone track forecast errors attributable to the initial state uncertainty and those attributable to the model imperfection. The average position error was reduced by replacing the initial conditions from the European Centre for Medium-range Weather Forecasts. The northward recurvature of Lupit (2009) was not reproduced with initial conditions from the Japan Meteorological Agency. It was consistent with the preceding study, indicating sensitivity to the initial state. The sensitivity to the model and the initial state was obtained. For Parma (2009), as opposed to the conclusion of the previous study, where Parma was discovered to be insensitive to the initial state, and the error was assumed to come from the model difference. Insensitivity to the initial vortex structures in the predicted tracks for Parma indicates that the error in the steering flow formed by the environmental field around tropical cyclone contributes to the northward bias.

著者

Takeshi ENOMOTO Shozo YAMANE Wataru OHFUCHI

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.93, no.2, pp.199-213, 2015 (Released:2015-05-14)

参考文献数

31

被引用文献数

8 10

---

Simple methods are formulated using an ensemble forecast to identify the sensitive initial perturbations that grow in a specified region at the verification time. These methods do not require the tangent-linear or adjoint models, but use an ensemble forecast to obtain approximated solutions. Input to the sensitivity calculation can be any ensemble forecast integrated from initial conditions perturbed with the bred vector, singular vector, or ensemble Kalman filter methods. Two formulations are presented here to approximate the adjoint and singular vector methods using an ensemble forecast. The ensemble singular vector sensitivity, which has already been applied in previous studies, is obtained with a single eigenvector calculation. The ensemble adjoint sensitivity only requires an even simpler matrix-vector multiplication. To validate the formulations, ensemble-based sensitivity analysis has been conducted in a few cases. First, the two methods were applied to identify the sensitive initial perturbations that grow in the verification region over Japan in January and August 2003. The first singular vector mode indeed achieves the largest amplitude at the verification time, but that is not necessarily true after the verification time. Both methods can identify the sensitive regions more specifically than the regions with large ensemble spread in cases with a mid-latitude cyclone and with a tropical cyclone. The monthly-mean sensitivity in January 2003 indicates the effect of Rossby waves and synoptic disturbances in upstream sensitive regions over Siberia, Tibet, and a downstream sensitive region in the north-western Pacific; the sensitivity in August 2003 suggests the influence of the Asian summer monsoon. Next, for an August 2002 storm case in Europe, global 20-km resolution simulations were conducted from the initial conditions perturbed by the ensemble singular vector method to compare with the unperturbed simulation. In the perturbed simulation, the cyclone is deeper by a few hPa in its north-east sector with more precipitation north of the Alps more consistently with observations. These results indicate that reasonable sensitive regions can be identified with our methods.

著者

Masahiro Shiozaki Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.103-108, 2021 (Released:2021-05-22)

参考文献数

22

被引用文献数

1

---

La Niña cases that occurred after 1948 are classified into cold and non-cold winters in the Far East to investigate the formation of disparate teleconnection patterns corresponding to the two types and to compare with those during El Niño. According to composite analyses using reanalysis datasets, the North Pacific Oscillation (NPO)/western Pacific (WP) pattern (NPO/WP pattern) and the Pacific-North American (PNA) pattern dominate in the cold and non-cold winters, respectively. As during El Niño, modulations of the local Hadley circulation associated with La Niña play an important role in the formation of the teleconnection patterns. These results indicate that the formation mechanisms of teleconnection patterns during La Niña are the same as those during El Niño but are not simple reverse signals.

著者

Masahrio Shiozaki Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-003, (Released:2019-12-30)

被引用文献数

1

---

The 2015/16 El Niño is compared with the two previous strongest events, the 1982/83 and 1997/98 El Niño. The 2015/16 winter features a basin warming in the Indian Ocean, a negative sea surface temperature (SST) anomaly shifted to the north in the western Pacific Ocean in addition to a positive SST anomaly shifted to the west in the eastern Pacific Ocean. These SST distributions lead to suppressed convection in the Maritime Continent, and to a weakened Hadley circulation in the western Pacific Ocean. The eastern Asian monsoon in the 2015/16 winter was also weakened due to the dominance of the western Pacific (WP) pattern. On the other hand, the third and fourth centers of action of Pacific/North American (PNA) pattern in the 2015/16 case are obscure. This may be due to weak divergence in the eastern Pacific Ocean.

著者

Takeshi ENOMOTO Hirokazu ENDO Yayoi HARADA Wataru OHFUCHI

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.87, no.1, pp.139-156, 2009 (Released:2009-03-07)

参考文献数

43

被引用文献数

13 14

---

In July 2004, torrential rainfalls caused significant damages in parts of Japan, followed by heat waves. Our data analysis shows that both rainfall and heat wave events in late Baiu season were caused by the intensification of the subtropical anticyclone near Japan (Bonin high) and that intensity of the Bonin high was significantly influenced by propagation of Rossby waves along the subtropical jet. Hindcast experiments from 15 July were conducted to study the mechanisms and predictability of these high-impact weather events. On 17-18 July, localized rainfalls at a few locations along the coast of the Sea of Japan including Sakata and Fukui were successfully simulated in a high-resolution (21-km mesh) global hindcast simulation. These rainfall events were found to occur near the leading edge of a filament of moist and warm air advected clockwise. On 20 July, anomalously high temperature was reproduced in the high-resolution hindcast simulation. With a moderate resolution of 83 km, the intensification of the subtropical anticyclone was reproduced although the föhn was much weaker. This result indicates that temperature distribution associated with föhn requires a resolution high enough to resolve major mountains. In order to investigate the predictability of propagation of Rossby waves and intensification of the Bonin high, 25-member ensemble experiments from 1 July 2004 were conducted using the moderate-resolution model. It is shown that the region along the Asian jet has twice as long predictability as the entire Northern Hemisphere. This case study suggests that the intensification of the Bonin high associated with the propagation of Rossby waves along the Asian jet could be predicted a few weeks in advance with an ensemble forecast at a moderate resolution.

著者

Yoshimi KAWAI Qoosaku MOTEKI Akira KUWANO-YOSHIDA Takeshi ENOMOTO Atsuyoshi MANDA Hisashi NAKAMURA

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.95, no.2, pp.71-90, 2017 (Released:2017-03-17)

参考文献数

31

被引用文献数

6

---

The present study investigated how impacts of the inclusion of radiosonde observations conducted locally in the early summer of 2012 over the Kuroshio and Kuroshio Extension (KE) can spread over time across the North Pacific basin to influence the predictability of synoptic and large-scale tropospheric circulation. For that purpose, observing system experiments (OSEs) were performed where each of two extra sets of radiosonde data, one obtained over the East China Sea in mid-May and the other over the KE in early July, was added to an atmospheric ensemble data assimilation system for comparison with the corresponding analyses without those data. The experiments show that the impact of the extra data assimilated propagates eastward mainly due to advection by the subtropical jet (STJ) in May and July. The strong STJ in May allows the upper-tropospheric impact to travel across the basin only within two days. Under the weaker STJ, the corresponding impact in July tends to remain within the western Pacific, until it eventually reaches the eastern portion of the basin. Assimilation of the extra radiosonde data over the Kuroshio or KE can lead to a decrease of pressure over the Gulf of Alaska in both May and July.  Additional forecast experiments based on the OSEs for May revealed that the pressure decrease over the Gulf of Alaska can be traced back to the west of the Alaska Peninsula and to the east of Japan over three days. The impacts that originate on different dates via different paths merge over the central North Pacific, reinforcing the cyclone over the Gulf of Alaska. This study presents examples where the impacts of atmospheric observations over the western boundary current can propagate across the ocean basin through the westerlies to influence the forecast skill in distant regions.

著者

Akira Yamazaki Takeshi Enomoto Takemasa Miyoshi Akira Kuwano-Yoshida Nobumasa Komori

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.41-46, 2017 (Released:2017-03-25)

参考文献数

26

被引用文献数

6

---

The observation operators in the local ensemble transform Kalman filter (LETKF) were improved to enable use of observations in the vicinity of the poles in the data assimilation system composed of the atmospheric general circulation model for the Earth Simulator (AFES) and the LETKF. The improved observation operators allow to assimilate the observations located south (north) of southernmost (northernmost) Gaussian grid latitudes. An algorithm for searching the nearest observations from an analyzed grid for error covariance localization was also modified to efficiently assimilate observations near the poles.The new algorithms were incorporated into the LETKF, and the impacts of routine radiosonde observations at the South Pole during the periods of July 2012 and January 2013 were assessed. The radiosonde observations suppressed an artificial expansion of the analysis ensemble spread which occasionally caused numerical instability in the upper troposphere and the lower stratosphere over the Antarctic regions. The analysis was also improved in the Antarctic regions.

著者

榎本 剛士 エノモト タケシ Takeshi Enomoto

雑誌

異文化コミュニケーション論集 = Intercultural communication review

巻号頁・発行日

vol.7, pp.119-133, 2009

著者

Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.4, pp.5-8, 2008 (Released:2008-01-26)

参考文献数

17

被引用文献数

5 5

---

A simple and accurate interpolation method applicable to semi-Lagrangian advection in a spectral global atmospheric model and downscaling is presented. The derivatives required for bicubic interpolation are usually represented by finite differences. Accuracy of bicubic interpolation is found to be improved by using derivatives calculated by the spectral method. Thus, the zonal and meridional derivatives are obtained by the Fourier and Legendre transforms, respectively. The proposed method is validated with the Gaussian hill rotation tests. The semi-Lagrangian advection model with this method produces a minimal error, comparable to that of the non-interpolating semi-Lagrangian model. In order to avoid the computationally expensive Legendre transforms, semi-spectral interpolation methods using only zonal spectral derivatives are also tested. Semi-spectral interpolation is found to be as accurate as full-spectral bicubic interpolation when quintic interpolation is used in the meridional direction.

著者

Takeshi Enomoto

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.6, pp.21-30, 2007-11-01 (Released:2020-02-19)

参考文献数

22

被引用文献数

8 10

---

The albedo of the ocean surface is of primary importance in the radiative energy balance of the Earth. It takes the smallest value of close to 0 over ocean water and the largest value of nearly 1 over snow-covered sea ice. The albedo of ocean water is determined by of the solar zenith angle, slope of the surface and optical properties of the atmosphere and ocean. The albedo of sea ice is significantly influenced by snow cover. During the warm season, ponds of melt water of snow and ice result in large reduction of albedo. Based on the knowledge from foregoing observational and modelling studies, the treatment of the ocean surface albedo in AFES (atmospheric general circulation model for the Earth Simulator) has been improved. Recent modifications to albedo parametrizations incorporated in AFES are described and optimum values for various parameters are adjusted to the observation data. The effects of albedo on global energy balance and atmospheric circulation are discussed.

著者

Kentaro Takai Takeshi Enomoto

出版者

The Pharmaceutical Society of Japan

雑誌

Chemical and Pharmaceutical Bulletin (ISSN:00092363)

巻号頁・発行日

vol.66, no.1, pp.37-44, 2018-01-01 (Released:2018-01-01)

参考文献数

67

被引用文献数

4

---

Among the muscarinic acetylcholine receptor (mAChR) subtypes, the M4 receptor has been investigated as a promising drug target for the treatment of schizophrenia. These investigations have been based on findings from M4-deficient mice studies as well as on the results of a clinical trial that used xanomeline, an M1/M4 mAChRs-preferring agonist. Both orthosteric agonists and positive allosteric modulators of M4 mAChR have been reported as promising ligands that not only have antipsychotic effects, but can also improve cognitive impairment and motor dysfunction. However, challenges remain due to the high homology of the orthosteric binding site among all muscarinic receptors. In this review, we summarize our approach to the identification of M4 mAChR activators, orthosteric agonists, and positive allosteric modulators based on M4 mAChR structural information and structure–activity relationship studies. These findings indicate that selective M4 mAChR activators are promising potential therapeutic agents for several central nervous system conditions.