著者

Shion Sekizawa Takafumi Miyasaka Hisashi Nakamura Akihiko Shimpo Kazuto Takemura Shuhei Maeda

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.15A-005, (Released:2019-05-22)

被引用文献数

34

---

During a torrential rainfall event in early July 2018, profound enhancement of moisture influx from the south and its convergence occurred over western Japan, which is investigated in this study on the basis of objective analysis and forecast data from the Japan Meteorological Agency Meso-Scale Model. The heavy rainfall over western Japan is found to accompany enhanced oceanic evaporation extensively around Japan, especially around the Kuroshio and entirely over the Sea of Japan. Linear decompositions of the anomalous moisture flux and surface latent heat flux anomalies applied to the high-resolution data reveals that the intensified speed of the low-level southerlies was the primary factor for the pronounced enhancement of both the moisture transport into the heavy rainfall region, especially in its western portion, and evaporation around the Kuroshio into the southerlies. An additional contribution is found from positive sea-surface temperature anomalies to the enhanced southerly moisture inflow into the eastern portion of the rainfall region. These findings have been confirmed through a backward trajectory analysis, which suggests that anomalous moisture supply to air parcels into the rainfall region primarily through the enhanced wind-forced evaporation roughly corresponds to about 10% of the precipitable water anomaly over western Japan.

著者

Akihiko Shimpo Kazuto Takemura Shunya Wakamatsu Hiroki Togawa Yasushi Mochizuki Motoaki Takekawa Shotaro Tanaka Kazuya Yamashita Shuhei Maeda Ryuta Kurora Hirokazu Murai Naoko Kitabatake Hiroshige Tsuguti Hitoshi Mukougawa Toshiki Iwasaki Ryuichi Kawamura Masahide Kimoto Izuru Takayabu Yukari N. Takayabu Youichi Tanimoto Toshihiko Hirooka Yukio Masumoto Masahiro Watanabe Kazuhisa Tsuboki Hisashi Nakamura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.13-18, 2019 (Released:2019-06-15)

参考文献数

22

被引用文献数

80

---

An extreme rainfall event occurred over western Japan and the adjacent Tokai region mainly in early July, named “the Heavy Rain Event of July 2018”, which caused widespread havoc. It was followed by heat wave that persisted in many regions over Japan in setting the highest temperature on record since 1946 over eastern Japan as the July and summertime means. The rain event was attributable to two extremely moist airflows of tropical origins confluent persistently into western Japan and large-scale ascent along the stationary Baiu front. The heat wave was attributable to the enhanced surface North Pacific Subtropical High and upper-tropospheric Tibetan High, with a prominent barotropic anticyclonic anomaly around the Korean Peninsula. The consecutive occurrence of these extreme events was related to persistent meandering of the upper-level subtropical jet, indicating remote influence from the upstream. The heat wave can also be influenced by enhanced summertime convective activity around the Philippines and possibly by extremely anomalous warmth over the Northern Hemisphere midlatitude in July 2018. The global warming can also influence not only the heat wave but also the rain event, consistent with a long-term increasing trend in intensity of extreme precipitation observed over Japan.

著者

Kazuto Takemura Shunya Wakamatsu Hiroki Togawa Akihiko Shimpo Chiaki Kobayashi Shuhei Maeda Hisashi Nakamura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.49-54, 2019 (Released:2019-08-09)

参考文献数

21

被引用文献数

1 29

---

This study investigates the influence of strong southerly moisture flux on an extreme rainfall event over western Japan in early July 2018, by using a global atmospheric reanalysis dataset. During its peak period from 5 to 7 July, extensive and unprecedented rainfall observed along the well-defined quasi-stationary Baiu front was attributed to two branches of extremely moist inflow from the southern confluence into western Japan. One was a shallow southerly airstream enhanced by the surface North Pacific Subtropical High, and the other was a deeper southwesterly airstream accompanying enhanced convection over the East China Sea. Both the vertically integrated moisture flux from the south and its convergence into western Japan reached the highest levels for 60 years due to an overwhelming contribution from the intensified southerlies. Anomalous diabatic heating associated with the active convection over the East China Sea acted to maintain the southwesterly moisture flux by inducing low-level cyclonic potential vorticity anomalies. During the rainfall event, a strong meander of the upper-level subtropical jet associated with the intensified surface North Pacific Subtropical High accompanied an amplified upper-level trough over the Korean Peninsula, which acted to induce ascent dynamically along the Baiu front.

著者

Shion Sekizawa Takafumi Miyasaka Hisashi Nakamura Akihiko Shimpo Kazuto Takemura Shuhei Maeda

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.25-30, 2019 (Released:2019-06-22)

参考文献数

10

被引用文献数

34

---

During a torrential rainfall event in early July 2018, profound enhancement of moisture influx from the south and its convergence occurred over western Japan, which is investigated in this study on the basis of objective analysis and forecast data from the Japan Meteorological Agency Meso-Scale Model. The heavy rainfall over western Japan is found to accompany enhanced oceanic evaporation extensively around Japan, especially around the Kuroshio and entirely over the Sea of Japan. Linear decompositions of the anomalous moisture flux and surface latent heat flux anomalies applied to the high-resolution data reveal that the intensified speed of the low-level southerlies was the primary factor for the pronounced enhancement of both the moisture transport into the heavy rainfall region, especially in its western portion, and evaporation around the Kuroshio into the southerlies. An additional contribution is found from positive sea-surface temperature anomalies to the enhanced southerly moisture inflow into the eastern portion of the rainfall region. These findings have been confirmed through a backward trajectory analysis, which suggests that anomalous moisture supply to air parcels into the rainfall region primarily through the enhanced wind-forced evaporation roughly corresponds to about 10% of the precipitable water anomaly over western Japan.

著者

Satoshi Iizuka Ryuichi Kawamura Hisashi Nakamura Toru Miyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.17A-004, (Released:2020-12-21)

被引用文献数

11

---

Typhoon Hagibis (2019) caused widespread flooding and damage over eastern Japan. The associated rainfall maxima were primarily observed on the windward mountain slopes along with the west of the leading edge of a low-level front. Concomitantly, a significant positive value in sea surface temperature anomalies (SSTAs) was observed in association with an ocean eddy over the Oyashio region, together with anomalous warmth over the entire western North Pacific. The present study examines the role of the SSTAs in the rainfall distribution associated with Hagibis, to deepen our understanding of the influence of the midlatitude ocean on tropical cyclones and associated rainfall. Our sensitivity experiments demonstrate that the observed warm SSTAs had the potential to displace the rainfall caused by Hagibis inland and thereby acted to increase precipitation along the Pacific coast of northeastern Japan. Our results suggest that midlatitude SSTAs on ocean-eddy scales can also influence the synoptic-scale atmospheric front and associated heavy rainfall.

著者

Ryusuke Masunaga Hisashi Nakamura Hirotaka Kamahori Kazutoshi Onogi Satoru Okajima

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.6-13, 2018 (Released:2018-01-18)

参考文献数

37

被引用文献数

1 14

---

As an additional product of the Japanese 55-year Reanalysis (JRA-55) project, a new global atmospheric reanalysis product, named JRA-55CHS, is under construction. It utilizes quarter-degree sea-surface temperature (SST) as lower-boundary condition with the same data assimilation system as the JRA-55 Conventional (JRA-55C), into which no satellite data is assimilated. The SST data can resolve steep SST gradients along the western boundary currents (WBCs), which are not necessarily well represented in many of the other atmospheric reanalysis products, including the JRA-55C. The present paper briefly documents basic performance of the JRA-55CHS, through comparing it with the JRA-55C and satellite observations in focusing on the major WBC regions. In the JRA-55CHS, mesoscale atmospheric structures along the WBCs are well reproduced in their climatological-mean fields as captured in the satellite observations. Their interannual- to decadal-scale variations associated with SST variations are also reasonably reproduced. The corresponding atmospheric features are less obvious in the JRA-55C owing to smoother SST prescribed. Furthermore, comparison between the two reanalysis products reveals that the influence of frontal-scale SST distributions can reach into the middle and upper troposphere, especially in summer. The JRA-55CHS will be useful for deepening our understanding of the nature of midlatitude frontal-scale air-sea interactions.

著者

Kazuaki Nishii Bunmei Taguchi Masato Mori Yu Kosaka Hisashi Nakamura

出版者

公益社団法人 日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.18, pp.199-204, 2022 (Released:2022-09-12)

参考文献数

23

---

Anomalous coldness was observed over midlatitude Eurasia in December 2020 and over subpolar Eurasia in January 2021. The former was accompanied by the Warm Arctic and Cold Eurasia (WACE) pattern, while the latter by the negative phase of the Arctic Oscillation (AO). A set of large ensemble experiments with an atmospheric general circulation model suggests a contribution of reduced Arctic Sea ice to the midlatitude cooling and WACE pattern in December 2020. The tropical and extratropical sea surface temperature (SST) anomalies, however, contribute to warming over midlatitude Eurasia. In January 2021, neither the sea ice nor SST anomalies can explain the subpolar Eurasian cooling and the negative AO in our experiments.

著者

Takeshi Horinouchi Yu Kosaka Hiroshi Nakamigawa Hisashi Nakamura Norihisa Fujikawa Yukari N. Takayabu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17B, no.Special_Edition, pp.1-8, 2021 (Released:2021-06-01)

参考文献数

30

被引用文献数

14

---

A prolonged heavy rainfall event occurred in Kyushu in early July 2020. Its large-scale environmental factors are investigated with observational and reanalysis data. Seven-day precipitation and moisture flux convergence around Kyushu were the greatest among the last 30 years. This pronounced convergence was maintained by nearly steady moisture influx, and the persistent upper-level trough to the northwest enhanced the ratio of moisture convergence to the influx. The magnitude of instantaneous moisture flux, however, was not particularly large among those along the subtropical jet axis or the Meiyu-Baiu rainband. What made this event unique is the persistence of the moisture flux peak anchored around Kyushu under the influence of the Silk-Road teleconnection. In June 2020, three upper-level troughs, whose easternmost one corresponding to the aforementioned trough, tend to form along the subtropical Asian jet. This wave train was persistent in the month and lasted until mid-July, 2020. Our analysis suggests that, prior to the rainfall event, the Silk-Road teleconnection was intensified through an interaction with a wave train at subpolar latitudes, which involves nonlinear processes including trough cut-off.

著者

Takeshi Horinouchi Yu Kosaka Hiroshi Nakamigawa Hisashi Nakamura Norihisa Fujikawa Yukari N. Takayabu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-019, (Released:2021-04-28)

被引用文献数

14

---

A prolonged heavy rainfall event occurred in Kyushu in early July 2020. Its large-scale environmental factors are investigated with observational and reanalysis data. Seven-day precipitation and moisture flux convergence around Kyushu were the greatest among the last 30 years. This pronounced convergence was maintained by nearly steady moisture influx, and the persistent upper-level trough to the northwest enhanced the ratio of moisture convergence to the influx. The magnitude of instantaneous moisture flux, however, was not particularly large among those along the subtropical jet axis or the Meiyu-Baiu rainband. What made this event unique is the persistence of the moisture flux peak anchored around Kyushu under the influence of the Silk-Road teleconnection. In June 2020, three upper-level troughs, whose easternmost one corresponding to the aforementioned trough, tend to form along the subtropical Asian jet. This wave train was persistent in the month and lasted until mid-July, 2020. Our analysis suggests that, prior to the rainfall event, the Silk-Road teleconnection was intensified through an interaction with a wave train at subpolar latitudes, which involves nonlinear processes including trough cut-off.

著者

Satoshi Iizuka Ryuichi Kawamura Hisashi Nakamura Toru Miyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17A, no.Special_Edition, pp.21-28, 2021 (Released:2021-02-23)

参考文献数

19

被引用文献数

11

---

Typhoon Hagibis (2019) caused widespread flooding and damage over eastern Japan. The associated rainfall maxima were primarily observed on the windward mountain slopes along with the west of the leading edge of a low-level front. Concomitantly, a significant positive value in sea surface temperature anomalies (SSTAs) was observed in association with an ocean eddy over the Oyashio region, together with anomalous warmth over the entire western North Pacific. The present study examines the role of the SSTAs in the rainfall distribution associated with Hagibis, to deepen our understanding of the influence of the midlatitude ocean on tropical cyclones and associated rainfall. Our sensitivity experiments demonstrate that the observed warm SSTAs had the potential to displace the rainfall caused by Hagibis inland and thereby acted to increase precipitation along the Pacific coast of northeastern Japan. Our results suggest that midlatitude SSTAs on ocean-eddy scales can also influence the synoptic-scale atmospheric front and associated heavy rainfall.

著者

Akihiko Shimpo Kazuto Takemura Shunya Wakamatsu Hiroki Togawa Yasushi Mochizuki Motoaki Takekawa Shotaro Tanaka Kazuya Yamashita Shuhei Maeda Ryuta Kurora Hirokazu Murai Naoko Kitabatake Hiroshige Tsuguti Hitoshi Mukougawa Toshiki Iwasaki Ryuichi Kawamura Masahide Kimoto Izuru Takayabu Yukari N. Takayabu Youichi Tanimoto Toshihiko Hirooka Yukio Masumoto Masahiro Watanabe Kazuhisa Tsuboki Hisashi Nakamura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.15A-003, (Released:2019-05-17)

被引用文献数

80

---

An extreme rainfall event occurred over western Japan and the adjacent Tokai region mainly in early July, named “the Heavy Rain Event of July 2018”, which caused widespread havoc. It was followed by heat wave that persisted in many regions over Japan in setting the highest temperature on record since 1946 over eastern Japan as the July and summertime means. The rain event was attributable to two extremely moist airflows of tropical origins confluent persistently into western Japan and large-scale ascent along the stationary Baiu front. The heat wave was attributable to the enhanced surface North Pacific Subtropical High and upper-tropospheric Tibetan High, with a prominent barotropic anticyclonic anomaly around the Korean Peninsula. The consecutive occurrence of these extreme events was related to persistent meandering of the upper-level subtropical jet, indicating remote influence from the upstream. The heat wave can also be influenced by enhanced summertime convective activity around the Philippines and possibly by extremely anomalous warmth over the Northern Hemisphere midlatitude in July 2018. The global warming can also influence not only the heat wave but also the rain event, consistent with a long-term increasing trend in intensity of extreme precipitation observed over Japan.

著者

Kazuaki NISHII Takafumi MIYASAKA Yu KOSAKA Hisashi NAKAMURA

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.3, pp.581-588, 2009 (Released:2009-07-08)

参考文献数

17

被引用文献数

10 11

---

A reanalysis dataset is used to establish the relationship between the year-to-year fluctuations in the midwinter storm-track activity over the Far East measured by poleward heat flux associated with subweekly disturbances and the occurrence of the first spring storm with strong southerly winds over Japan (Haru-Ichiban). Our analysis reveals that its early (delayed) occurrence tends to follow the enhanced (suppressed) winter storm-track activity with less (more) apparent minimum in midwinter in the course of the seasonal march. A metric is defined on the basis of the eddy heat flux to measure the reproducibility of the particular seasonal march of the Far East storm-track activity simulated in each of the Coupled Model Intercomparison Project Phase 3 climate models under the present climate. Under a particular global warming scenario, ensemble projection based only on the several models that show the highest reproducibility of the storm-track activity measured with the particular metric indicates that the future enhancement is likely in the midwinter storm-track activity associated with the weakening of the East Asian winter monsoon, implying that Haru-Ichiban is likely to occur earlier in the late 21st century than in the 20th century.

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

Toshihiko Takemura Hisashi Nakamura Masayuki Takigawa Hiroaki Kondo Takehiko Satomura Takafumi Miyasaka Teruyuki Nakajima

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.7, pp.101-104, 2011 (Released:2011-07-02)

参考文献数

13

被引用文献数

72 80

---

The powerful tsunami generated by the massive earthquake that occurred east of Japan on March 11, 2011 caused serious damages of the Fukushima Daiichi Nuclear Power Plant on its cooling facilities for nuclear reactors. Hydrogen and vapor blasts that occurred until March 15 outside of the reactors led to the emission of radioactive materials into the air. Here we show a numerical simulation for the long-range transport from the plant to the U.S. and even Europe with a global aerosol transport model SPRINTARS. Large-scale updraft organized by a low-pressure system traveling across Japan from March 14 to 15 was found effective in lifting the particles from the surface layer to the level of a westerly jet stream that could carry the particles across the Pacific within 3 to 4 days. Their simulated concentration rapidly decreases to the order of 10-8 of its initial level, consistent with the level detected in California on March 18. The simulation also reproduces the subsequent trans-Atlantic transport of those particles by a poleward-deflected jet stream, first toward Iceland and then southward to continental Europe as actually observed.