著者

Tetsuya Kawano Rina Yasukiyo Ryuichi Kawamura Takashi Mochizuki

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

pp.2023-014, (Released:2023-05-10)

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Downscaling simulations of MIROC6 (the sixth version of Model for Interdisciplinary Research on Climate) data using the Weather Research and Forecasting (WRF) model were performed to investigate future changes in the Japan Sea polar airmass convergence zones (JPCZs) related to heavy snowfall events in the Sea of Japan–side region of central and northern Japan. WRF downscaling simulations showed a northward shift of JPCZs and the associated changes in precipitation distribution. Rainfall increased significantly over the central part of the Sea of Japan and in the Tohoku region. On the other hand, snowfall decreased significantly over the entire Sea of Japan. However, there was a significant increase in snowfall in the inland mountainous areas of the Tohoku region. Jet streaks shift northward in the future climate, which was confirmed in the MIROC6 data. Reflecting such future environments, WRF downscaling simulations showed that a mesoscale cyclonic circulation anomaly passing over Hokkaido from the Sea of Japan, which is not resolved by MIROC6, contributes to the northward shift of JPCZs and the associated changes in rainfall and snowfall.

著者

Keita Fujiwara Ryuichi Kawamura Tetsuya Kawano

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.151-156, 2020 (Released:2020-08-09)

参考文献数

22

被引用文献数

5

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This study investigated the remote impact of an increase in latent heat flux (LHF) over the Kuroshio on tropical cyclone (TC) development, using a cloud-resolving model. A control run and a sensitivity experiment with Kuroshio's LHF artificially enhanced were performed for Typhoon Chaba in 2010. The TC development simulated in the sensitivity experiment was suppressed as compared with the control run. The sensitivity experiment demonstrated that eyewall convection and the associated TC secondary circulation were suppressed by a decrease in equivalent potential temperature (θe) around the eyewall through the lower θe penetration into the inner core region in the boundary layer. The dynamic features of the TC were also altered by the attenuated TC secondary circulation through the inhibition of the inward advection of the absolute angular momentum. The super-gradient tangential velocities in the inner core were smaller than those in the control run. Such thermodynamic and dynamic changes were remotely induced by the decrease in moisture import from the Kuroshio. Since the increased LHF facilitated the development of a surface low over the Kuroshio, the intensified low further accumulated the Kuroshio's vapor and suppressed low-level northeasterlies toward the TC, resulting in interrupting the moisture import into the TC.

著者

Rimpei Kamamoto Kenji Suzuki Tetsuya Kawano Hiroshi Hanado Katsuhiro Nakagawa Yuki Kaneko

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.115-119, 2020 (Released:2020-07-04)

参考文献数

12

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Two products from the Global Precipitation Measurement (GPM) Dual-frequency Precipitation Radar (DPR) algorithms, a flag of intense solid precipitation above the −10°C height (“flagHeavyIcePrecip”) and a classification of precipitation type (“typePrecip”) were validated by ground-based hydrometeor measurements and X-band multi-parameter (X-MP) radar observations of snow clouds on 4 February 2018. Contoured frequency by altitude diagrams of the X-MP radar reflectivity exhibited a significant difference between footprints flagged and unflagged by the “flagHeavyIcePrecip” algorithm, which indicated that the algorithm is reasonable. The hydrometeor classification (HC) by the X-MP radar, which was confirmed by microphysical evidence from ground-based hydrometeor measurements, suggested the existence of graupel in the footprints with “flagHeavyIcePrecip”. In addition, according to the information of the GPM DPR, the “flagHeavyIcePrecip” footprints were characterized by not only graupel but also large snowflakes. According to the information of X-MP radar HC, the “typePrecip” algorithm by the detection of “flagHeavyIcePrecip” was effective in classifying precipitation types of snow clouds, whereas it seems that there is room for improvement in the “typePrecip” algorithms based on the extended-DPRm-method and H-method.

著者

Rimpei Kamamoto Kenji Suzuki Tetsuya Kawano Hiroshi Hanado Katsuhiro Nakagawa Yuki Kaneko

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-020, (Released:2020-06-03)

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Two products from the Global Precipitation Measurement (GPM) Dual-frequency Precipitation Radar (DPR) algorithms, a flag of intense solid precipitation above the −10°C height (“flagHeavyIcePrecip”) and a classification of precipitation type (“typePrecip”) were validated by ground-based hydrometeor measurements and X-band multi-parameter (X-MP) radar observations of snow clouds on 4 February 2018. Contoured frequency by altitude diagrams of the X-MP radar reflectivity exhibited a significant difference between footprints flagged and unflagged by the “flagHeavyIcePrecip” algorithm, which indicated that the algorithm is reasonable. The hydrometeor classification (HC) by the X-MP radar, which was confirmed by microphysical evidence from ground-based hydrometeor measurements, suggested the existence of graupel in the footprints with “flagHeavyIcePrecip”. In addition, according to the information of the GPM DPR, the “flagHeavyIcePrecip” footprints were characterized by not only graupel but also large snowflakes. According to the information of X-MP radar HC, the “typePrecip” algorithm by the detection of “flagHeavyIcePrecip” was effective in classifying precipitation types of snow clouds, whereas it seems that there is room for improvement in the “typePrecip” algorithms based on the extended-DPRm-method and H-method.

著者

Tetsuya Kawano Ryuichi Kawamura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.1-5, 2018 (Released:2018-01-18)

参考文献数

21

被引用文献数

5

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To investigate the influence of the distribution of sea ice in the Sea of Okhotsk on the behavior of a severe snowstorm, which occurred in Hokkaido, Japan, on 2 March 2013 and which was associated with an explosive cyclone, three WRF simulations with realistic, reduced, and enhanced sea ice-cover were carried out. A comparison among these experiments reveals that the extent of the sea ice influenced low-level temperatures and winds to the rear of the cyclone center during the development of the explosive cyclone over the Sea of Okhotsk. Sea ice insulates the ocean from heat exchange with the atmosphere. As a result, when the Okhotsk sea ice extent reaches Hokkaido Island, cold air masses from the north traverse the island without first being heated by the ocean. The consequent temperature reduction produces a low-level higher pressure region to the rear of the cyclone center. As a result, a large geopotential gradient is generated just to the rear of the cyclone center, and low-level winds are intensified within this region. Therefore, the Okhotsk sea ice extent reaching Hokkaido Island plays a significant role in lowering temperatures and intensifying winds in the island.

著者

Tetsuya Kawano Ryuichi Kawamura

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.205-210, 2022 (Released:2022-09-28)

参考文献数

29

被引用文献数

1

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In this study, we investigated the remote effect of warm sea surface temperatures (SSTs) in the Kuroshio region of the East China Sea (ECS) on heavy rainfall that occurred in southern Kyushu, Japan, on 3 July 2020 using the Weather Research and Forecasting model. To examine the effect, a simulation with realistic SSTs and two simulations with reduced SSTs in the ECS Kuroshio region were performed. Backward- and forward-trajectory analyses showed that low-level parcels in the simulation with warmer SSTs in the ECS Kuroshio region possessed larger amounts of water vapor than those in the reduced-SST experiments. The difference in the water-vapor amounts of low-level parcels between the simulations with warmer and colder SSTs remained until the parcels started to ascend in the heavy rainfall area. In addition, there were many more parcels with extremely large amounts of water vapor in the simulation with warmer SSTs. Such an increase in low-level water-vapor amounts under warmer SST conditions in the ECS Kuroshio region led not only to enhancement of the precipitation source but also to atmospheric destabilization, resulting in the production of a large amount of precipitation.

著者

Tetsuya Kawano Ryuichi Kawamura

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

pp.2022-033, (Released:2022-08-05)

被引用文献数

1

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In this study, we investigated the remote effect of warm sea surface temperatures (SSTs) in the Kuroshio region of the East China Sea (ECS) on heavy rainfall that occurred in southern Kyushu, Japan on 3 July 2020 using the Weather Research and Forecasting model. To examine the effect, a simulation with realistic SSTs and two simulations with reduced SSTs in the ECS Kuroshio region were performed. Backward- and forward-trajectory analyses showed that low-level parcels in the simulation with warmer SSTs in the ECS Kuroshio region possessed larger amounts of water vapor than those in the reduced-SST experiments. The difference in the water-vapor amounts of low-level parcels between the simulations with warmer and colder SSTs remained until the parcels started to ascend in the heavy rainfall area. In addition, there were many more parcels with extremely large amounts of water vapor in the simulation with warmer SSTs. Such an increase in low-level water-vapor amounts under warmer SST conditions in the ECS Kuroshio region led not only to enhancement of the precipitation source but also to atmospheric destabilization, resulting in the production of a large amount of precipitation.

著者

Kenji Suzuki Katsuhiro Nakagawa Tetsuya Kawano Shuichi Mori Masaki Katsumata Fadli Syamsudin Kunio Yoneyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.148-152, 2018 (Released:2018-10-17)

参考文献数

20

被引用文献数

3

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Videosonde observations were conducted at the southwestern coastal region of Sumatra Island, Indonesia, as part of a pilot field campaign of the Years of the Maritime Continent project (Pre-YMC), to investigate the role of solid hydrometeor for precipitation processes in clouds. Videosondes were launched into three types of clouds: convective and stratiform clouds, and a thick upper stratiform cloud with shallow convection at lower level. A quantitative evaluation of the graupel shape data obtained from the videosondes showed different graupel formations in different rain systems. For the typical stratiform cloud, almost no graupel was observed. In contrasts, for the thick upper stratiform clouds with shallow convection, large numbers of ice crystals in the upper layer suggested to act as embryos and form a lot of graupel with the riming of the supercooled droplets that was supposed to be provided from the shallow convection. On the other hand, for the convection case, the videosonde observed spherical graupel just above the freezing level. This suggested that frozen drops acting as embryos formed spherical graupel, which were uplifted by the strong updraft in the convective cloud, and were different from the generally irregular-shaped graupel in the thick upper stratiform cloud.

著者

Eigo TOCHIMOTO Tetsuya KAWANO

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.4, pp.217-237, 2017 (Released:2017-07-04)

参考文献数

39

被引用文献数

4

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In Part I of this study, the development processes of Baiu frontal depressions (BFDs) have been examined through case-study numerical experiments. The numerical simulations revealed that latent heating is dominant for the development of BFDs in the western part of the Baiu frontal zone (W-BFDs), west of approximately 140°E, while both latent heating and baroclinicity are important for the development of BFDs in the eastern part of the zone (E-BFDs), east of approximately 140°E. In this study, idealized numerical simulations with zonally homogeneous basic fields are conducted to obtain a more generalized perspective of the development processes of BFDs. The basic fields for the idealized simulations are made from the composites of the environments under which 28 W-BFDs and 43 E-BFDs developed. The idealized simulations successfully reproduce a realistic W-BFD and E-BFD. The W-BFD has a slightly westward-tilted vertical structure, modulated by latent heating at low levels of the atmosphere. In contrast, the E-BFD has a westward-tilted structure through the troposphere, similar to the well-known baroclinic wave structure. Results of available potential energy diagnosis for the effects of latent heating and baroclinicity on the BFD development are consistent with those in Part I. The W-BFD has a mechanism mainly driven by latent heating yielding strong convection, while the E-BFD develops through baroclinic instability in moist atmosphere.

著者

Keita Fujiwara Ryuichi Kawamura Tetsuya Kawano

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-026, (Released:2020-07-03)

被引用文献数

5

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This study investigated the remote impact of an increase in latent heat flux (LHF) over the Kuroshio on tropical cyclone (TC) development, using a cloud-resolving model. A control run and a sensitivity experiment with Kuroshio's LHF artificially enhanced were performed for Typhoon Chaba in 2010. The TC development simulated in the sensitivity experiment was suppressed as compared with the control run. The sensitivity experiment demonstrated that eyewall convection and the associated TC secondary circulation were suppressed by a decrease in equivalent potential temperature (θe) around the eyewall through the lower θe penetration into the inner core region in the boundary layer. The dynamic features of the TC were also altered by the attenuated TC secondary circulation through the inhibition of the inward advection of the absolute angular momentum. The super-gradient tangential velocities in the inner core were smaller than those in the control run. Such thermodynamic and dynamic changes were remotely induced by the decrease in moisture import from the Kuroshio. Since the increased LHF facilitated the development of a surface low over the Kuroshio, the intensified low further accumulated the Kuroshio's vapor and suppressed low-level northeasterlies toward the TC, resulting in interrupting the moisture import into the TC.