著者

Toru Miyama Takuya Hasegawa

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.10, pp.5-9, 2014 (Released:2014-02-06)

参考文献数

24

被引用文献数

3 9

---

A regional atmospheric model was employed to demonstrate that a strong westerly wind, which occurred around December 2001 prior to the 2002/03 El Niño event, was enhanced by sea surface temperature gradient along the equator in the western Pacific warm pool region. Furthermore, a regional oceanic model was employed to demonstrate that the enhanced westerly wind event substantially increased oceanic Kelvin wave response along the equatorial Pacific Ocean.

著者

Tetsuya Takemi

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.10, pp.158-162, 2014 (Released:2014-10-10)

参考文献数

14

被引用文献数

1 8

---

This study investigates the characteristics of local-scale afternoon rainfall and its environmental conditions in and around the Nobi Plain under synoptically undisturbed conditions in summer by using operational meteorological data. The analysis of radar/raingauge analyzed precipitation data revealed that strong rainfall occurs over the mountain slopes in late afternoon and in the northern part of the Nobi Plain in early evening, while light rain frequently occurs around the mountain peaks in early afternoon. Examining mesoscal analysis data indicated that the primary difference in the environmental conditions that distinguish between rain and no-rain days is middle-level moisture field, with moister condition being found on rain days. Because of the significant difference in the middle-level moisture, stability index is useful in distinguishing the environmental conditions between rain and no-rain days.

著者

Hiroyuki Iwasaki

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.10, pp.98-102, 2014 (Released:2014-06-06)

参考文献数

19

被引用文献数

4 7

---

Features of lightning around Japan over a four-year period are described using World Wide Lightning Location Network data based on global observations of very low frequency radio waves. Lightning density over land is lower than that over the ocean and the oceanic area of high density runs along the Kuroshio Current. The zone of highest density is found to the west of the Nansei Islands; however, very strong lightning rarely occurs there. Conversely, lightning density decreases gradually towards the eastern part of the Kuroshio Current, where the occurrence of very strong lightning increases.The ratio of very strong lightning in most of the analysis area tends to increase in the cold season, and it becomes large in areas where lightning frequency is low. Furthermore, both very weak and strong lightning have a tendency to occur in areas where rain intensity is not strong.

著者

吉崎 正憲

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.57, no.6, pp.548-559, 1979 (Released:2007-10-19)

参考文献数

13

被引用文献数

3

---

振幅方程式を用いて,カーブした温度分布を持ち,しかもシアのある流れのある流体中に実現する対流セルの形状を調べた.温度分布の一次関数からのずれとシア流の強さ,および系のレーリー数の臨界値からのずれをパラメータとして,定常解を求めてその安定性を調べた.系のレーリー数のカーブした温度分布に対する臨界値からのずれを(ΔR)*とすると,次の事が明らかになった.(1)シアが弱い場合,2次元ロールは(ΔR)*が限られた領域でのみ不安定で存在しない.しかし,シアがある値以上強くなると,ロール解は(ΔR)*が正の領域で常に安定に存在する.(2)シアがない時に六角形セルに帰着する解は,シアが強まるにつれて,シアの方向に伸びたセルに変形してゆく.そしてシアがある値以上になると,この解は安定に存在しなくなる.

著者

Hiroaki Miura Takafumi Maeda Masahide Kimoto

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.8, pp.165-169, 2012 (Released:2012-12-28)

参考文献数

27

被引用文献数

1 2

---

A pair of 20-year simulations by two different versions of MIROC (Model for Interdisciplinary Research on Climate) was examined by using a standardized set of Madden-Julian Oscillation (MJO) diagnostics. One of the major differences between version 4 (MIROC4) and version 5 (MIROC5) of MIROC is the cumulus parameterization scheme. MIROC4 uses a prognostic Arakawa-Schubert scheme, whereas MIROC5 uses the Chikira scheme. MIROC5 reproduced the MJO better than MIROC4: a stronger signal in the wavenumber-frequency diagram, a slower and more noticeable eastward movement in the lag-correlation plot, and a better phase relationship between outgoing longwave radiation and zonal winds.To investigate the impact of mid-tropospheric humidity on cumulus development in MIROC5, the atmosphere-only version of MIROC5 was used for a series of sensitivity runs, each with different entrainment parameter values. The entrainment parameter settings significantly influenced the simulated MJO. Large-scale cloud systems tended to move westward with smaller entrainment parameter values, accompanied by a pair of rotations with quasi-symmetry about the equator in the lower troposphere, whereas eastward movements were faster, with larger entrainment parameter values.

著者

折笠 成宏 村上 正隆

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.75, no.6, pp.1033-1039, 1997-12-25 (Released:2009-09-15)

参考文献数

8

被引用文献数

4 22

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低濃度の氷晶からなる巻雲を測定するために新型の雲粒子ゾンデを開発した。このゾンデは倍率の異なる2台の小型ビデオカメラを搭載しており、粒径7μm-5mmの粒子の映像を1.6GHzのマイクロ波を通して地上に伝送する。従来の雲粒子ゾンデでは、サンプリング体積が小さいために、雲粒子の数濃度が低い雲の粒径分布が正確に評価できなかった。この点を克服するために、吸引用の小型ファンを付加することによって十分なサンプリング体積を確保した。また、周囲の気圧変化やゾンデの上昇速度によるサンプリング体積の変化を室内実験によって評価した。捕捉率の理論的計算から、10μm以上の粒子が全て捕捉されると考えられる。強制吸引式雲粒子ゾンデによる巻雲の観測例から、10μm以上の氷晶の粒径分布を250m間隔で精度良く決定できることがわかった。この雲粒子ゾンデの観測結果は、巻雲の生成や維持の機構を理解するのに有益な情報を与える。

著者

Tsuyoshi Yamaura Yoshiyuki Kajikawa Hirofumi Tomita Masaki Satoh

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.9, pp.89-93, 2013 (Released:2013-07-17)

参考文献数

21

被引用文献数

3 5

---

The impact of a tropical cyclone on the northward migration of the Baiu frontal zone (BFZ) is investigated in the case of the tropical cyclone MAWAR (2012) using a global cloud-system resolving model, called NICAM. From 4 to 6 June in 2012, the BFZ rapidly shifts northward with MAWAR. A simulation with the initial data of 29 May reproduces the northward migration of the BFZ and the tropical cyclone. Strong southerlies on the eastern side of the tropical cyclone transport moist and high-temperature air into the BFZ. This horizontal advection affects the northward migration of the BFZ. In contrast, the BFZ stagnates to the south of Japan in another simulation with the initial data of 30 May because the tropical cyclone track is diverted eastward. Thus, realistic reproducibility of a tropical cyclone is needed for better simulations and prediction of the BFZ migration.

著者

Hiromu Seko Kazuo Saito Masaru Kunii Masayuki Kyouda

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.5, pp.57-60, 2009 (Released:2009-04-15)

参考文献数

11

被引用文献数

2 6 4

---

Energy Helicity Index (EHI), defined by the product of Convective Available Potential Energy (CAPE) and Storm Relative Environmental Helicity (SREH), is one of potential parameters to diagnose the possibility of tornado outbreak. In this study, probabilities that EHI exceed some criteria were examined with a mesoscale ensemble prediction system, whose grid interval was 15 km, in two tornado events in Japan (Nobeoka and Saroma tornado events). High probability regions (HPR, hereafter) of large SREH existed in the northeastern quadrants of a typhoon or a low-pressure system, while HPRs of large CAPE extended along the warm humid airflow from the Pacific Ocean. In the two events, the tornados were formed near HPRs of large EHI, where HPRs of large SREH and CAPE were overlapped. This result indicates the possibility of the probability forecast of the potential parameter for tornado outbreak.

著者

徳山 源次郎

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.2, no.6, pp.184-189, 1924-11-15 (Released:2009-02-05)

---

The author picked up 21 case of newly born cyclones in Japan Sea from the end of 1920 to June 1923. They appear mostly in the winter months i.e. Month Oct. Nov. Dec. Jan. Feb. march April June Frequency 1 2 3 4 5 2 1 2 of these cyclones 5 classes may be distinguished with respect to their birth places. He examined the condition prevailing before or at the time of the birth of the cyclones and noticed that a characteristic sudden rises and falls of temperature were always seen. Thus he insists that the cyclones may be the products on the lines of iscontinuity, developing from the horizontal vorticity effected by the orographic conditions as S. Fujiwhara has already has already suggested. The author recommends the hourly observations in order to issue timely warning against the sudden break out of the cyclone of the kind. (S. F.)

著者

Brett T. HOOVER Rolf H. LANGLAND

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.6, pp.369-389, 2017 (Released:2017-11-14)

参考文献数

22

被引用文献数

3

---

This study examines analysis and forecast impacts in the Navy Global Environmental Model (NAVGEM) from direct assimilation of temperature and wind “pseudo-raob” profiles derived from analysis fields of the European Centre for Medium-Range Weather Forecasting-Integrated Forecast System (ECWMF-IFS). The pseudo-raob profiles are provided on eight vertical levels from 250 hPa to 1000 hPa on a 1° × 1° resolution rectilinear grid and are assimilated as synthetic observation data by NAVGEM at 0000 UTC and 1200 UTC for an experimental time period of 48 days. The pseudo-raob observations are assumed in these experiments to have observation errors identical to temperature and wind data provided by conventional radiosonde observations.  In this diagnostic context, the assimilation of pseudo-raob profiles significantly reduces temperature and height biases in the NAVGEM analysis and provides general improvements to forecast skill when verified against both self-analysis and rawinsondes. Reduction of NAVGEM temperature bias is most evident in southern hemisphere high latitudes, where the assimilation of pseudo-raob information mitigates NAVGEM temperature bias and indicates sub-optimal bias correction of radiance data in the NAVGEM Control analysis. Despite the revisiting of assimilated observation information when assimilating pseudo-raobs from the IFS analysis into the NAVGEM analysis, improvement to the NAVGEM analyses and forecasts is both statistically significant and consistent across several verification techniques. This suggests that there are likely small effects from any correlations between pseudo-raob data and the NAVGEM background. The assimilation of pseudo-raob data also reduces the total observation impact in NAVGEM as estimated by the adjoint model, which is an indicator of general improvement to analysis and forecast quality.

著者

Hiroaki Miura

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.69-73, 2017 (Released:2017-04-25)

参考文献数

18

被引用文献数

3

---

A shallow water model is developed on the regular hexagonal mesh by combining the hexagonal B1-grid and B2-grid schemes. The new scheme called as the hexagonal synchronized B-grid (SB-grid) scheme in this work allows avoiding a computational mode problem of the ZM-grid scheme. It is known that the problem is caused by the mismatch of degrees of freedoms of the prognostic variables. The SB-grid uses the same variable arrangement as the ZM-grid, placing fluid depths and fluid velocities at the centers and corners of hexagonal cells, respectively, but the nonlinear terms of the momentum equation are discretized using wider spatial stencils than those of the ZM-grid. This change results in the inhibition of extra interactions in the velocity fields that enhances a computational mode in the ZM-grid. Geostrophic adjustment tests on a regular hexagonal mesh confirm that the SB-grid shallow water model behaves almost equivalently to the Z-grid model, and the computational mode problem is certainly settled down.

著者

Yasumitsu Maejima Masaru Kunii Takemasa Miyoshi

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.174-180, 2017 (Released:2017-09-27)

参考文献数

37

被引用文献数

14

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This study aims to investigate the impacts of 30-second-update and 100-m-resolution data assimilation (DA) on a prediction of sudden local torrential rains caused by an isolated convective system in Kobe city on 11 September 2014. We perform a Local Ensemble Transform Kalman filter (LETKF) experiment with the Japan Meteorological Agency non-hydrostatic model (JMA-NHM) at 1-km and 100-m resolution using every-30-second radar reflectivity observed by the phased array weather radar (PAWR) at Osaka University. The 1-km-mesh experiment shows that 30-second-update PAWR DA has positive impacts on the analyses and forecasts. Moreover, the 100-m-mesh experiment shows significant advantages in representing the rainfall intensity and fine structure of the convective system. The promising results suggest that 30-second-update, 100-m-mesh DA have a great potential for predicting sudden local rain events.

著者

Shaoping WANG Yongjian DING Fengqing JIANG Muhammad Naveed ANJUM Mudassar IQBAL

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.5, pp.287-299, 2017 (Released:2017-09-16)

参考文献数

47

被引用文献数

11

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Northern Xinjiang (NX), China, located at the middle latitude of the Northern Hemisphere, has abundant snowfall and a long period of snow cover. In this study, to assess the impact of climate change in this region and to provide scientific knowledge for the resource management, analyses of the spatial and temporal variations in extreme snowfall events (ESEs) in NX was conducted based on five defined ESE indices: days of heavy snowfall (DHS), maximum 1-day snowfall amount (MASD), maximum 1-event snowfall amount (MASE), the maximum number of consecutive snowfall days (MDSE), and frequency of heavy snowfall events (HSE). To reconstruct the snowfall dataset, the relationship between air temperature and snowfall events was determined, and it was found that the daily minimum air temperature below 0°C is the best indicator to identify snowfall days. ESEs in NX occupied an increasing proportion of snow events, although the number of snowfall days decreased. Consistent increasing trends in all ESE indices were found for the entire NX region, while different changes in these indices were noted between subregions. With highly increasing trends of these ESE indices in most of subregions, the Daxigou–Xiaoquzi and Qitai areas were the hotspots for ESEs. Since these hotspots are likely influenced by airflow from the Arctic Ocean, the changes in the Arctic Ocean and the associated atmospheric circulation resulting from climate change might be the main reasons for the increasing trend of ESEs in NX.

著者

KAMAE Youichi MEI Wei XIE Shang-Ping

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

pp.2017-027, (Released:2017-09-07)

被引用文献数

53

---

Eddy transport of atmospheric water vapor from the tropics is important for rainfall and related natural disasters in the middle latitudes. Atmospheric rivers (ARs), intense moisture plumes typically associated with extratropical cyclones, often produce heavy precipitation upon encountering topography on the west coasts of mid-latitude North America and Europe. ARs also occur over the northwestern Pacific and sometimes cause floods and landslides over East Asia, but the climatological relationship between ARs and heavy rainfall in this region remains unclear. Here, we evaluate the contribution of ARs to the hydrological cycle over East Asia using high-resolution daily rainfall observations and an atmospheric reanalysis during 1958–2007. Despite their low occurrence, ARs account for 14–44% of total rainfall and 20–90% of extreme heavy-rainfall events during spring, summer and autumn seasons. AR-related extreme rainfall is especially pronounced over western-to-southeastern slopes of terrains over the Korean Peninsula and Japan, owing to strong orographic effects and a stable direction of low-level moisture flows. A strong relationship between warm-season AR heavy rainfall and preceding-winter El Niño is identified since the 1970s, suggesting the potential of predicting heavy-rainfall risk over Korea and Japan at seasonal leads.

著者

吉松 隆三郎

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.15, no.4, pp.158-160, 1937-04-05 (Released:2009-02-05)

被引用文献数

3

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Eliminating the so-called universal variations with two independent base lines, we find that earth-currents va_??_ in some manner with the activity of the earthquakes and their after shocks. The relation between the mode of the variation of earth-currents and mechanism of earthquake is not clear at the present time.

著者

Jiangman WANG Chun LI

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.3, pp.199-211, 2017 (Released:2017-05-27)

参考文献数

28

被引用文献数

10

---

The Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO) are the two dominant low-frequency modes in the North Pacific. This study focused on the simulation capability of the two leading low-frequency modes in current-coupled models, based on 24 coupled model outputs from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Results showed that most of these models captured the two low-frequency modes, but the air–sea coupling relationship (covariability of the ocean low-frequency modes with the atmospheric forcing modes) captured by CMIP5 models had drastic differences. Four models (CCSM4, CESM-WACCM, MIROC5, and NorESM1-M) not only captured the spatial and temporal characteristics of the PDO and NPGO modes but also simulated their air–sea coupling relationships. Therefore, we selected these four models to examine changes in the PDO and NPGO modes under different global warming scenarios using RCP4.5 and RCP8.5 forcing (RCP: Representative Concentration Pathway). In future RCP scenarios, the spatial patterns of PDO and NPGO showed no obvious changes. However, the dominant periods of the PDO and NPGO modes were shorter, which is consistent with faster oceanic Rossby waves induced by enhanced upper oceanic stratification in the warming scenarios.

著者

Genta Ueno Tomoyuki Higuchi Takashi Kagimoto Naoki Hirose

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.3, pp.5-8, 2007 (Released:2007-01-31)

参考文献数

19

被引用文献数

7 17

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We report an application of the ensemble Kalman filter (EnKF) and smoother (EnKS) to an intermediate coupled atmosphere-ocean model of Zebiak and Cane, into which the sea surface height (SSH) anomaly observations by TOPEX/POSEIDON (T/P) altimetry are assimilated. Smoothed estimates of the 54,403 dimensional state are obtained from 1,981 observational points with 2,048 ensemble members. While assimilated data are SSH anomalies alone, the estimated sea surface temperature (SST) anomalies reproduce primary temporal characteristics of the actual SST. The smoothed estimate of the zonal wind anomalies is also consistent with the observation except for the westerly anomalies in the western Pacific.

著者

Yanfeng ZHAO Donghai WANG Zhaoming LIANG Jianjun XU

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.111-125, 2017 (Released:2017-03-17)

参考文献数

41

被引用文献数

6

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Persistent severe rainfall (PSR) events during the rainy season (April to July) in southern China were studied in terms of the dynamic features of the large-scale circulation. The aim of the study was to understand the formation mechanism and improve forecasting. The circulation field and spatiotemporal distribution of waves at 500 hPa for different types of PSR were analyzed. The results reveal the following: (1) During the pre-flood season (April to June) in southern China, troughs have the same phase in the middle latitudes as those in the high latitudes. The East Asia major trough (3–5 wave numbers) in the middle latitudes strengthens southwards and interacts with the 30°N subtropical high (1–2 wave numbers) from three days prior to the PSR events. (2) During the post-flood season (June to July) in South China, the weather regime transitions occur on five days prior to the PSR events. The 40°N trough (2–4 wave numbers) strengthens southwards and interacts with the subtropical high (1–2 wave numbers). It is also affected by the blocking ridge (3 wave number) in the high latitudes. (3) During the Mei-yu period (June to July) over the Yangtze–Huaihe River basin, the transitions of circulation pattern start three days prior to the PSR events. With the northwest development of the subtropical high, there is a transfer process from long to short waves in terms of energy for the trough at 50°N.

著者

Ryuji YOSHIDA Yoshiaki MIYAMOTO Hirofumi TOMITA Yoshiyuki KAJIKAWA

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.1, pp.35-47, 2017 (Released:2017-03-01)

参考文献数

29

被引用文献数

11

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The environmental conditions for tropical cyclone genesis are examined by numerical experiment. We focus on the case of a non-developing disturbance showed features for tropical cyclone genesis in the Pacific Area Long-term Atmospheric observation for Understanding climate change in 2010 (PALAU2010) observation campaign over the western North Pacific. We clarify the importance of the presence of abundant moisture around the disturbance for continuous convection and demonstrate that the collocation of a mid-level vortex and a low-level vortex, i.e., the persistence of an upright structure of vortices, is important in tropical cyclone genesis. We conduct two numerical experiments using the Weather Research and Forecasting Model Advanced Research WRF model in double nested domains with a horizontal grid space of 27 km and 9 km for the outer domain and the inner domain, respectively. The first experiment is based on reanalysis data (a control experiment) and the second includes increased water vapor content over the northwestern dry area of the disturbance. In the control experiment, the disturbance did not develop into a tropical cyclone in spite of the existence of the mid-level and low-level vortices. In contrast, the sensitivity experiment shows that a tropical cyclone was formed from the disturbance with increased water vapor content. The presence of persistent upright vortices was supported by continuous convection until the genesis of the tropical cyclone.

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.1, pp.4-5, 2017 (Released:2017-03-01)

参考文献数

5

被引用文献数

1