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

Kazuto Takemura Akihiko Shimpo

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.75-79, 2019 (Released:2019-04-06)

参考文献数

20

被引用文献数

1

---

Herein, (i) the remote influence of positive Indian Ocean Dipole (P-IOD) events in enhancing Tibetan High and (ii) its impact on the East Asian climate, from July to September, is analyzed based on composite analysis and linear baroclinic model experiment. In the equatorial Indian Ocean, convective activity enhances over the western part and suppresses over the eastern, which is associated with the zonal contrast of the sea surface temperature anomaly during P-IOD events. A lower-tropospheric clockwise circulation anomaly is evident from the eastern equatorial Indian Ocean where the suppressed convection is seen to the Indochina Peninsula. The streamlines arrive at the seas east of the Philippines, contributing to the enhancement of the monsoon trough. In the upper troposphere, crucial divergence anomaly over a wide area in the western North Pacific and the associated stronger-than-normal northward divergent winds toward East Asia cause strong northward negative-vorticity advection over the northern part of East Asia, contributing to the northeastward extension of the Tibetan High. This circulation anomaly contributes to both the significantly hot conditions in boreal summer and the late-summer heat over East Asia.

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.