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
1

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
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
1

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
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
2

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
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)

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
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
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
KODAMA Shinichi SATOH Masaki
出版者
公益社団法人 日本気象学会
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2022-046, (Released:2022-08-03)

During the autumn rainy season, typhoons located far from Japan sometimes cause significant precipitation in Japan. In this study, we characterized remote precipitation events in September for 40 years from 1980 to 2019. We also analyzed cases in which remote precipitation did not occur despite approaching typhoons, as well as cases in which heavy precipitation was not affected by typhoons. We characterized the environmental fields of the remote precipitation cases by comparing them with these other two types of cases. Statistical analysis showed that remote precipitation tended to occur when the typhoons were located over the southern or southwestern oceans of mainland Japan and when the tracks of the typhoons were northward or changing to the northeast. The composite analysis of the remote precipitation cases showed that the subtropical high was retreating to the east for the two days before the remote precipitation. By contrast, the cases in which remote precipitation did not occur showed the opposite pattern: the subtropical high was strengthening to the west when typhoons were approaching over the southern or southwestern oceans of the Japanese archipelago. Furthermore, the remote precipitation occurred to the equatorward jet streak entrance of the 200 hPa jet, whereas the 200 hPa jet streak was shifted to the west in the cases where remote precipitation did not occur. The vertical cross-section of the northward water vapor flux showed that the northward water vapor inflow from the middle troposphere was larger in cases of remote precipitation than in cases in which heavy precipitation was not caused by typhoons. In addition, dynamical analysis showed that the area of remote precipitation corresponded to the region of 800-600 hPa mean quasi-geostrophic forcing for ascent and 925 hPa frontogenesis.
著者
Takashi Maki Taichu Y. Tanaka Tsuyoshi Koshiro Atsushi Shimizu Tsuyoshi T. Sekiyama Mizuo Kajino Yasunori Kurosaki Toshiya Okuro Naga Oshima
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.2022-035, (Released:2022-09-06)

Ensemble future climate projections were performed using the Meteorological Research Institute Earth System Model version 2.0 (MRI-ESM2.0) for sand and dust storms (SDS), which have a significant social, economic, and climatic impact on East Asia. A past replication experiment using MRI-ESM2.0 reproduced the decreasing trend of SDS in the Gobi Desert in the early 21st century. Prediction experiments by MRI_ESM2.0 in CMIP6 future scenarios indicated no significant differences in the total amount of SDS emissions in the Gobi Desert for 2015-2100; however, SDS emissions increased with warmer scenarios in spring and autumn. In particular, March in the highest warming scenario (SSP5-8.5) exhibited an annual increase rate in SDS emissions of 3.0% for 2015-2100. Friction velocity was the factor most highly correlated with SDS emissions, with a correlation generally higher than 0.6 for all climate scenarios throughout the year. In spring and autumn, snow cover exhibited a low negative correlation with SDS emissions, while ground temperature exhibited a positive correlation. The increase in SDS emissions and subsequent dust transport by midlatitude westerlies in spring and autumn in the accelerated warming scenarios is likely due to the changes in friction velocity and erodibility due to the decrease in snow accumulation.
著者
Masashi Niwano Masami Suya Koichi Nagaya Satoru Yamaguchi Sumito Matoba Ikuo Harada Nozomu Ohkawara
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.193-198, 2022 (Released:2022-09-07)
参考文献数
34

Despite the importance of seasonal snow in Japan, quantitative information on seasonal snow mass in the whole area is lacking. To understand the current mass balance of seasonal snow cover, we develop a method to quantify the mass balance of seasonal snow all over Japan using the Japan Meteorological Agency's operational regional atmospheric model, Local Forecast Model (LFM), as well as the snow physics model, Snow Metamorphism and Albedo Process (SMAP). Our model simulations using the LFM-SMAP model chain show that the seasonal snow water equivalent (SWE) evolution is mostly controlled by snowfall and runoff. It is estimated that the seasonal peak area-integrated SWE in Japan reaches 42.2 Gt on average during the 2017-2022 winters, and 60.1 Gt (+43% with respect to the average) and 22.0 Gt (−48%) during relatively heavy (2017-2018) and relatively light (2019-2020) snow years, respectively. The ratios between seasonal peak area-integrated SWE and winter-accumulated (November to February) snowfall amounts for the heavy, average, and light snow years are 83%, 74%, and 59%, respectively.
著者
Takehiko Kobori Masayuki Maki Yasushi Fujiyoshi Masato Iguchi Seiji Fukushima
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.2022-037, (Released:2022-09-09)

We developed a method for estimating the height and growth rate of volcanic eruption columns, at high-temporal resolution, by processing vertical cross-sectional images of areas around the crater obtained with a marine radar tilted on its side. We applied our method to 127 eruptions occurring at Sakurajima (Kagoshima, Japan) from June to December 2019 and successfully estimated the time-series height of the eruption column and its growth rate every 2.5 seconds. In 48 cases, we obtained the maximum height of the eruption column and confirmed that these results were consistent with those estimated using meteorological radar. Although the maximum height estimated with our method tended to be lower than that observed by monitoring cameras, results could be obtained even when observations were difficult due to cloud effects, etc.
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
vol.18, pp.181-186, 2022 (Released:2022-08-31)
参考文献数
32

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
Masashi Niwano Masami Suya Koichi Nagaya Satoru Yamaguchi Sumito Matoba Ikuo Harada Nozomu Ohkawara
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.2022-031, (Released:2022-08-11)

Despite the importance of seasonal snow in Japan, quantitative information on seasonal snow mass in the whole area is lacking. To understand the current mass balance of seasonal snow cover, we develop a method to quantify the mass balance of seasonal snow all over Japan using the Japan Meteorological Agency's operational regional atmospheric model, Local Forecast Model (LFM), as well as the snow physics model, Snow Metamorphism and Albedo Process (SMAP). Our model simulations using the LFM-SMAP model chain show that the seasonal snow water equivalent (SWE) evolution is mostly controlled by snowfall and runoff. It is estimated that the seasonal peak area-integrated SWE in Japan reaches 42.2 Gt on average during the 2017-2022 winters, and 60.1 Gt (+43% with respect to the average) and 22.0 Gt (−48%) during relatively heavy (2017-2018) and relatively light (2019-2020) snow years, respectively. The ratios between seasonal peak area-integrated SWE and winter-accumulated (November to February) snowfall amounts for the heavy, average, and light snow years are 83%, 74%, and 59%, respectively.
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
pp.2022-027, (Released:2022-06-23)

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 (‘certainty’, ‘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
Michiya Hayashi Hideo Shiogama
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.96-103, 2022 (Released:2022-05-17)
参考文献数
47

The technique for composing a small subset of global climate models is critical to provide climate scenarios for impact and adaptation studies of regional climate changes. A recent study developed a novel statistical method for selecting a mini-ensemble of five climate models from the Coupled Model Intercomparison Project Phase 6 for widely capturing different future projections of Japanese climate across eight atmospheric variables at the surface. However, it remains unclear which mini-ensemble model contributes to efficiently covering the full projection ranges. Here, we rank each mini-ensemble projection around Japan among a full ensemble, showing that the selected five models capture the full ranges without systematic biases, except for relative humidity. Furthermore, we find that the widespread global warming level contributes to covering well the projection uncertainties in the daily-mean, maximum and minimum air temperatures and downward longwave radiation but not in precipitation, solar radiation, relative humidity, or wind speed. As the last four variables are sensitive to various factors, such as large-scale circulation and aerosol-forcing changes, rather than global-mean temperature changes, the model selection method featured here is preferable for capturing the wide future projection ranges in Japan.

5 0 0 0 OA 日本海の地震

著者
長谷川 謙
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.37, no.6, pp.203-207, 1918-06-10 (Released:2009-02-05)
被引用文献数
6