著者

Shion Sekizawa Tsubasa Kohyama

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.2022-021, (Released:2022-05-26)

被引用文献数

10

---

On January 15, 2022, the volcano Hunga Tonga about 8000-km away from Japan explosively erupted. Following the eruption, tsunami-like sea-level fluctuations were observed in Japan, much earlier than expected based on the oceanic long-wave propagation from Tonga. By contrast, atmospheric pressure disturbance presumably due to the eruption was also observed about 30 minutes before the sea-level change. Therefore, the observed sea-level fluctuations can be considered as meteotsunamis forced by the pressure perturbation rather than tectonically forced by the eruption, but the mechanism is not yet fully understood. This study attempts to understand the nature of this meteotsunami by using a simple one-dimensional shallow-water model. The results show that the time and amplitude of the observed sea-level changes are consistent with the simulated sea-level changes forced by the atmospheric forcing. A set of experiments with different bathymetry profiles also reveals the importance of amplification due to near-Proudman resonance over deep basins and the shoaling effect over the continental slope, while extremely deep and narrow topography such as trenches is of second-order importance.

著者

髙根 雄也 伊藤 享洋

出版者

公益社団法人 日本気象学会

雑誌

天気 (ISSN:05460921)

巻号頁・発行日

vol.68, no.3, pp.149-163, 2021 (Released:2021-04-30)

参考文献数

42

---

2020年8月17日に静岡県浜松市で観測された日最高気温の歴代最高タイ記録41.1℃について,関連する観測データの特徴を調査した.まず,高温の背景要因を考察した結果,鯨の尾型に準ずる夏型気圧配置の出現とそれに伴う850hPa面の高温・概ね北西の一般風,東海地方における梅雨明け以降の連続晴天がその要因として示唆された.次に,高温の直接的な要因を考察したところ,伊吹山地を吹き下りる気流に伴うフェーン現象と,その後この気流が名古屋都市圏の地表面付近を吹走する際の顕熱供給(非断熱加熱)で気流そのものが高温化するメカニズムで浜松の高温がある程度説明できることが明らかになった.この高温化した風が浜松へ侵入し,浜松のすぐ東側の南風と収束したことが,浜松で最も気温が高くなった要因とみられる.以上のメカニズムは過去の国内における高温事例のメカニズムと類似していることから,上記の背景要因と直接的要因を兼ね備えうる他の地域においても今後40℃を超える高温が発生する可能性がある.

著者

Ger Anne W. Duran Joseph Q. Basconcillo

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.19, pp.33-41, 2023 (Released:2023-02-22)

参考文献数

32

---

Due to less tropical cyclone (TC) occurrences, the climatology of the quiescent TC season (i.e., March-April-May, MAM) in the western North Pacific (WNP) is less understood when compared to the more active season (i.e., June-November). Here we show observational evidence of significantly decreasing TC quiescence during MAM that can be attributed to more Central Pacific El Niño events from 2002 to 2022. A Central Pacific El Niño is related to an asymmetric sea surface temperature (SST) pattern where warm (cool) SST anomalies are concentrated in the central (western) Pacific, which consequently contributes to the overall decrease in TC quiescence in MAM. Such anomalous SST pattern prompts the western North Pacific Subtropical High to expand westward, creating a conducive large-scale environment for TC development and allowing TCs to move closer to the landmass, which ultimately leads to an increasing cost of TC-associated damages during the quiescent season. Our study provides new insights into the decreasing TC quiescence and TC climatology in the WNP during MAM, which is ultimately expected to contribute to disaster risk reduction in the region.

著者

Ryuho Kataoka Stephen D. Winn Emile Touber

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.116-121, 2022 (Released:2022-06-11)

参考文献数

8

被引用文献数

3

---

Large-amplitude meteotsunamis were observed in many areas in Japan, following the arrival of barometric Lamb waves emitted by an underwater volcanic eruption of Hunga Tonga-Hunga Ha‘apai in January 2022. We modeled the power spectra of the tidal level data obtained from 12 tide stations of the Geospatial Information Authority of Japan, based on a method of transfer function which converts the barometric pressure pulse spectra into the meteotsunami spectra. The obtained transfer functions are similar at 12 stations. The pressure pulse spectra are obtained from the ensemble average of ∼1500 Soratena weather sensors of Weathernews Inc. distributed over Japan. The observed meteotsunami spectra can be characterized by the enhanced seiche eigenmodes at each station excited by the mesoscale pressure pulse within the amplitude error of 50%, which contributes for accumulating the necessary knowledge to understand the potential dangers in various different areas over Japan.

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)

---

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

Shion Sekizawa Tsubasa Kohyama

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.129-134, 2022 (Released:2022-06-21)

参考文献数

13

被引用文献数

10

---

On 15 January 2022, the volcano Hunga Tonga about 8000-km away from Japan explosively erupted. Following the eruption, tsunami-like sea-level fluctuations were observed in Japan, much earlier than expected based on the oceanic long-wave propagation from Tonga. By contrast, atmospheric pressure disturbance presumably due to the eruption was also observed about 30 minutes before the sea-level change. Therefore, the observed sea-level fluctuations can be considered as meteotsunamis forced by the pressure perturbation rather than tectonically forced by the eruption, but the mechanism is not yet fully understood. This study attempts to understand the nature of this meteotsunami by using a simple one-dimensional shallow-water model. The results show that the time and amplitude of the observed sea-level changes are consistent with the simulated sea-level changes forced by the atmospheric forcing. A set of experiments with different bathymetry profiles also reveals the importance of amplification due to near-Proudman resonance over deep basins and the shoaling effect over the continental slope, while extremely deep and narrow topography such as trenches is of second-order importance.

著者

藤部 文昭 松本 淳 鈴木 秀人

出版者

公益社団法人 日本気象学会

雑誌

天気 (ISSN:05460921)

巻号頁・発行日

vol.66, no.8, pp.513-527, 2019 (Released:2019-09-30)

参考文献数

26

被引用文献数

1

---

1999~2016年の人口動態統計の個票データを使って,低温死亡率の空間・時間変動と気温との関係を統計的に調べた.空間分布においては,気温の低い都道府県ほど低温死亡率の高い傾向があり,冬季(12~3月)の平均気温1℃当たりの死亡率の変化は約12%である.年々変動においては,冬季(12~3月)の平均気温が1℃低い年は死亡率が20%程度高い.季節変化においては,12~3月の死亡数が年間の78%を占める.また日々変動においては,日平均気温1℃当たり死亡率は15%程度変動する.以上の事実は低温死亡率が気温の地域的・時間的な変動に影響されることを示しているが,熱中症に比べると気温変動に対する低温死亡率の変化率は小さい.また,冬の前半に比べて後半は低温死亡率が低いなど,低温馴化を示唆する事実がある一方で,低温馴化に否定的な事実もあり,馴化の影響は熱中症の場合ほどには明瞭でない.

著者

Ger Anne W. Duran Joseph Q. Basconcillo

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.2023-005, (Released:2023-01-20)

---

Due to less tropical cyclone (TC) occurrences, the climatology of the quiescent TC season (i.e., March-April-May, MAM) in the Western North Pacific (WNP) is less understood when compared to the more active season (i.e., June-November). Here we show observational evidence of significantly decreasing TC quiescence during MAM that can be attributed to more Central Pacific El Niño events from 2002 to 2022. A Central Pacific El Niño is related to an asymmetric sea surface temperature (SST) pattern where warm (cool) SST anomalies are concentrated in the central (western) Pacific, which consequently contributes to the overall decrease in TC quiescence in MAM. Such anomalous SST pattern prompts the Western North Pacific Subtropical High to expand westward, creating a conducive large-scale environment for TC development and allowing TCs to move closer to the landmass, which ultimately leads to an increasing cost of TC-associated damages during the quiescent season. Our study provides new insights into the decreasing TC quiescence and TC climatology in the WNP during MAM, which is ultimately expected to contribute to disaster risk reduction in the region.

著者

山田 将喜 釜江 陽一

出版者

公益社団法人 日本気象学会

雑誌

天気 (ISSN:05460921)

巻号頁・発行日

vol.69, no.11, pp.609-620, 2022 (Released:2022-12-31)

参考文献数

36

---

令和3年8月中旬の大雨をはじめ,近年の東アジアでは,総観規模の水蒸気流入に伴って広い範囲で大雨となる事例が立て続けに発生している.中緯度で発生する細長くのびた水蒸気輸送帯は「大気の川」と呼ばれ,西日本や中部地方で暖候期に発生する強い降水との関係性が指摘されている.本研究では,日降水量の閾値を地域・季節ごとに設定することで,寒候期や北日本を含め,大気の川に伴って日本列島上の広い範囲で起こる強い降水の気候学的な特徴を調査した.寒候期には,大気の川による強い降水は西日本から中部地方にかけての太平洋側で発生する.6月から7月にかけては,東西にのびた前線に沿って大気の川が形成され,西寄りの水蒸気の流れ込みによって北陸から東北地方日本海側に2日以上続く強い降水をもたらす.夏季から秋季にかけては,日本の南海上に存在する台風から南寄りの水蒸気流が流れ込み,南北にのびた大気の川が発生することで,西日本から北日本の広い範囲で強い降水が2日以上続くことがある.

著者

Keita Fujiwara 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.2022-029, (Released:2022-07-25)

被引用文献数

2

---

This study investigated a recent tendency of interannual precipitation variations during the Baiu season (June–July) in southern Kyushu, Japan. Long-term satellite precipitation observations revealed a significant amplification of the interannual variability of Baiu precipitation after the beginning of this century and the appearance of a quasi-quadrennial variation (QQV). Composite analyses with respect to the unstable regime of Baiu activity when the QQV prevailed suggested a possible link between the Indo-western Pacific Ocean Capacitor (IPOC) mode and the QQV. Regression analyses with an IPOC index showed the dominance of an anomalous anticyclone in the lower troposphere centered over the South China Sea and the Philippine Sea and enhanced poleward moisture transport along its western periphery. The interdecadal shift in remote IPOC influence seen around the year 2000 featured the westward (northward) extension of the low-level anomalous anticyclone toward the Bay of Bengal (southern Japan); consequently, the significant moisture flux convergence area covered southern Kyushu during the unstable Baiu regime, consistent with the QQV appearance during the same period. It is also inferred that the IPOC mode modulation may come from the increased impact of central Pacific El Niño/Southern Oscillation on the IPOC in recent decades.

著者

長岡 半太郎

出版者

公益社団法人 日本気象学会

雑誌

氣象集誌. 第1輯 (ISSN:00261165)

巻号頁・発行日

vol.40, no.7, pp.193-203, 1921-07-10 (Released:2009-02-05)

著者

Tomoe Nasuno Masuo Nakano Hiroyuki Murakami Kazuyoshi Kikuchi Yohei Yamada

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.88-95, 2022 (Released:2022-05-13)

参考文献数

38

被引用文献数

3

---

In this study, we explored the impacts of midlatitude western North Pacific (WNP) sea surface temperature (SST) on tropical cyclone (TC) activity at intraseasonal to seasonal time scales during the 2018 boreal summer. During this period, a positive SST anomaly occurred in the midlatitude WNP and subtropical central Pacific; TC activity was abnormally high under the influence of the strong Asian summer monsoon. We performed sensitivity experiments using a global cloud system-resolving model for global SST (control, CTL) and SST that were regionally restored according to midlatitude WNP climatology (MWNPCLM). TC track density in the eastern WNP was higher in CTL than in MWNPCLM, in association with large-scale atmospheric responses; enhanced monsoon westerlies in the subtropical WNP, moist rising (dry subsiding) tendencies, and reduced (enhanced) vertical wind shear in the eastern (western) WNP. Enhanced TC activity in the eastern WNP was more distinct for intense TCs and during the active phase of intraseasonal oscillation (ISO). These results suggest that the impacts of midlatitude SST anomalies can reach lower latitudes to affect TC activity via large-scale atmospheric responses and ISO, which are usually overwhelmed by the impacts of SST anomalies in the tropics and subtropics.

著者

吉森 正和

出版者

公益社団法人 日本気象学会

雑誌

天気 (ISSN:05460921)

巻号頁・発行日

vol.66, no.3, pp.214-219, 2019 (Released:2019-04-30)

参考文献数

17

著者

Yukie Moroda Kazuhisa Tsuboki Shinsuke Satoh Katsuhiro Nakagawa Tomoo Ushio Hiroshi Kikuchi

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.110-115, 2022 (Released:2022-06-08)

参考文献数

16

---

A rapid rise of the lightning activity center in the upper part of a cloud is called a lightning bubble (LB). It remains unclear how LBs occur in thunderstorm clouds. Recently, high-spatiotemporal resolution data obtained by a phased array weather radar enabled observation of temporal changes in the three-dimensional structure of precipitation cores in a precipitation cell. To understand the mechanism by which LBs occur, we examined the relationship between the time-evolution of precipitation cores and the flash initiation points. After a precipitation core developed in an isolated thundercloud, the top height of the core reached its highest altitude and then started to descend. Meanwhile, the echo tops above the core continued to rise, which is termed an upward reflectivity pulse (URP). Over an hour, nine URPs were successively observed in the thundercloud. The average tracking period of the URPs was 3.9 minutes. Flash initiation points appeared near the highest points of the URPs and continued to rise with time. These observational results suggest that URPs cause LBs by enhancing the electric field, via the separation of graupel and ice crystals near the highest points of ascending URPs.

著者

筒井 百平

出版者

公益社団法人 日本気象学会

雑誌

氣象集誌. 第1輯 (ISSN:00261165)

巻号頁・発行日

vol.34, no.11, pp.719-721, 1915-11-10 (Released:2009-02-05)

著者

Yasutaka Hirockawa Teruyuki Kato

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.167-172, 2022 (Released:2022-07-27)

参考文献数

21

---

The procedures for identifying and classifying heavy rainfall areas of linear-stationary type (LS-HRAs) from the distributions of radar/raingauge-analyzed precipitation amounts (RAP) were improved to extract “senjo-kousuitai” with elongated and stagnant characteristics that causes localized heavy rainfall in Japan. The improved procedures were verified based on subjective judgments (‘certain’, ‘doubtful’, and ‘suspect’) whether LS-HRAs possess the characteristics of typical senjo-kousuitai. Criteria for excluding LS-HRAs judged to be ‘suspect’, mainly associated with tropical cyclones (TCs) and non-stationary mesoscale convective systems, were introduced to optimally extract senjo-kousuitai events. The criteria were determined by the distance between LS-HRAs and TC centers (DLT), the maximum total RAP of LS-HRA (total RAP), and the properties of each RAP distribution at every hour during the LS-HRA extraction period, e.g., DLT ≤ 500 km and total RAP < 200 mm. By applying these criteria, 372 senjo-kousuitai events were extracted from 452 LS-HRAs during the warm seasons (April–November) in 2009-2020, although approximately 35% of the LS-HRAs judged to be ‘suspect’ were not excluded. The criteria associated with TCs excluded them more effectively than the other factors. The improved procedures for extracting senjo-kousuitai events are expected to be used effectively for their statistical analyses.

著者

水科 七三郎

出版者

公益社団法人 日本気象学会

雑誌

氣象集誌. 第1輯 (ISSN:00261165)

巻号頁・発行日

vol.1, no.1, pp.23-25, 1882 (Released:2006-03-27)

著者

Kenji Kai Kei Kawai Kazuma Ohara Yuki Minamoto Yoshitaka Jin Teruya Maki Jun Noda Tatsuo Shiina Enkhbaatar Davaanyam

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.19, pp.269-273, 2023 (Released:2023-11-03)

参考文献数

17

---

The mass concentration of Asian dust in the atmosphere is an essential parameter of the atmospheric environment in East Asia. In April 2016, we conducted simultaneous observations using an optical particle counter (OPC) installed on a tethered balloon and a ceilometer in the Gobi Desert. We estimated the mass-extinction conversion factor MECF (gm−2) from the relationship between the dust extinction coefficient and dust mass concentration obtained by simultaneous observations. The MECF at Dalanzadgad in the Gobi Desert is 2.16 gm−2 at 910 nm and 1.91 gm−2 at 532 nm. A previous study on Asian dust showed that the values of the MECF were 1.78 gm−2 in Beijing, 1.40 gm−2 in Seoul, 1.18 gm−2 in Tsukuba (Japan), and 1.04 gm−2 at averaged AD-Net lidar stations in Japan. The MECF values decreased from the Asian dust source to the lee-side areas. This result suggests that the MECF depends on the size distribution of the dust.

著者

Daisuke Sugiyama Ryo Onishi Hironori Fudeyasu

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.19, pp.246-252, 2023 (Released:2023-10-21)

参考文献数

13

---

This study proposes a deep learning approach called SolaCam to accurately estimate solar radiation from the images captured by cameras. The proposed SolaCam performs deep learning by utilizing both image features and theoretical maximum solar radiation that vary with time and location. The trained model is capable of accurately estimating solar radiation on the ground surface from sky images captured by smartphones, fixed-point cameras, and other devices. The developed SolaCam can use a remote sensing function, which estimates solar radiation, on inexpensive camera-equipped devices.

著者

Kenji Suzuki Yurika Hara Takuji Sugidachi Kensaku Shimizu Masatomo Fujiwara

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.19, pp.261-268, 2023 (Released:2023-10-31)

参考文献数

28

被引用文献数

1

---

A new particle imaging radiosonde “Rainscope” has been developed, and for the first time, particle fall velocity measurement functionality was added to a balloon-borne device. Rainscope can capture a clear still image of precipitation particles in a cloud when they interrupt an infrared beam, using a CMOS camera equipped with an electronic shutter. It can also record the time when a particle passes the upper and lower built-in infrared sensors, enabling measurement of the velocity of falling precipitation particles. For ground testing in rain and snow, a ground-based Rainscope showed raindrop/snowflake size-fall velocity distributions similar to those obtained in previous studies. In a comparison with a Parsivel2 disdrometer in rain, the Rainscope results were in good agreement with the distributions obtained by an adjacent Parsivel2. In a test flight of Rainscope into a stratiform cloud, raindrops, mostly melted particles, snowflakes in the process of melting, graupel, and snowflakes were observed. It was observed that the fall velocity varied depending on the type of solid precipitation particles.