著者

MURATA Akihiko WATANABE I. Shun-ichi SASAKI Hidetaka KAWASE Hiroaki NOSAKA Masaya

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2019-035, (Released:2019-02-04)

被引用文献数

7

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A novel method for detecting tropical cyclones in high-resolution climate model simulations is proposed herein and subjected to examination. The proposed method utilizes a two-dimensional scatterplot based on two quantities that represent the radial gradient and the tangential asymmetry of mid-to upper-level thickness around a simulated vortex. A comparison between the modeled and observed tropical cyclones using the non-hydrostatic regional climate model (NHRCM) with 20-km grid spacing under reanalysis-driven boundary conditions for one year revealed that no cyclones were missed and there was only one false alarm over a part of the western North Pacific near Japan. The simulated vortices were classified into two categories; tropical cyclones and extratropical cyclones. These two groups, having specific features, were also found in the results using present-day climate datasets, indicating that the tropical cyclones were reasonably distinguished from extratropical cyclones although a one-by-one comparison could not, in principle, be conducted. Comparison of the results obtained from datasets with 5-km and 20-km grid spacing demonstrated that the detection scheme was only weakly dependent on the horizontal resolution. This dependence was further reduced by using the radial gradient over the outer radii instead of near the center of the vortex. The resolution-independent feature in this method is due to a procedure in which the tangential asymmetry of mid-to upper-level thickness is utilized instead of the relative vorticity at 850 hPa, often used in conventional schemes. This procedure allows the method to identify tropical cyclones without the need to determine a grid-dependent threshold. The method proposed here provides a useful tool for detecting tropical cyclones in high-resolution climate simulations.

著者

DING Jinfeng CHEN Yangquan WANG Yuan XU Xin

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2019-002, (Released:2018-10-05)

被引用文献数

5

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The Southeasterly Gale in Xinjiang, China is a severe local gale weather phenomenon which occasionally happens near the northwest opening of Tianshan Grand Canyon. On 8 June 2013, a strong southeasterly gale attacked Urumchi with an average ground wind velocity of 15 m s-1, and gust speed that reached 30 m s-1. The gale lasted for over 24 hours making it the strongest wind in latest 20 years. Through observations and numerical simulation, this study represents the formation of this southeasterly gale incident. The large-scale topographic forcing of the Tianshan Mountains led to the intensification of pressure gradient across the Tianshan Grand Canyon, and therefore an advantageous condition for the generation of the southeasterly gale had been provided. When air currents travelled through the canyon, a critical layer with zero wind velocity was established, and nonlinear process was activated by orographic forcing. It is suggested that air current sank on the northwest opening of the canyon due to unstable stratification and thus strengthened the gale.

著者

田中 博 野原 大輔 横井 みずほ

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.78, no.5, pp.611-630, 2000-10-25 (Released:2009-09-15)

参考文献数

13

被引用文献数

9 14

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本研究では、韓国のIce Valleyと福島県の中山風穴の現地観測結果を基に、0次元モデル、流路に沿った1次元モデル、鉛直断面としての2次元モデルを開発して、風穴循環の一連の数値シミュレーションを行なった。これらの風穴は、周辺の稀少な高山植物の生育により国の特別天然記念物に指定されているが、近年氷の減少傾向が見られ、その原因究明が急務となっている。現地観測および数値実験の結果として、以下のことが明らかになった。(1)風穴循環の主な駆動力は、外気と崖錘内部の気温差による水平気圧傾度力である。(2)崖錘内部の空気の滞留時間は約2日であり、平均的な風穴循環は、約1mm/sと推定される。(3)春から夏にかけてのカタバ風としての冷風穴循環は、秋から冬にかけてのアナバ風としての温風穴循環と入れ替わる。(4)崖錘表面に植生が殆どないIce Valleyの場合、夏季の安定したカタバ流とは対照的に冬季には不安定による対流混合が発生し、このような風穴循環の夏冬非対称性が、崖錘内部の平均温度を下げる熱フィルターの役割を果たす。外気が暑ければ暑いほど、崖錘内部のカタバ風が強くなることは注目に値する。Ice Valleyや中山風穴における夏期氷結の謎は、部分的ではあるが、この風穴循環のメカニズムによって説明することができる。

著者

TAKASAKI Yoshinori YOSHIZAKI Masanori SUZUKI-PARKER Asuka WATARAI Yasushi

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2019-026, (Released:2018-12-24)

被引用文献数

5

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The Okazaki heavy rainfall event, which occurred at midnight on 28 August 2008 around Okazaki city in Japan, was produced by a quasi-stationary band-shaped precipitation system. This precipitation system remained quasi-stationary for approximately 5 hours over Okazaki city and the surrounding area, and produced prolonged intense precipitation. This study presents sensitivity numerical experiments to examine the impact of surrounding mountainous topography on the quasi-stationarity of the precipitation system using the Weather Research and Forecasting (WRF) model with 500 m horizontal resolution. In an experiment without the mountains to the east of Okazaki city, the quasi-stationary precipitation system was not reproduced. On the other hand, experiments including eastside mountains produced a low-level convergence in south of Okazaki city, resulting in the quasi-stationary precipitation system and prolonged precipitation as observed near Okazaki city. The convergence was formed by sustained easterlies together with northerly winds blowing in west of Okazaki city. The easterlies were maintained by westward shift of southeasterly inflow from the Pacific Ocean due to the enhanced pressure gradient on the upstream side of the eastside mountains in the low-level atmosphere with low Froude numbers (Fr < 0.5). The easterlies also steadily supplied warm and moist air to the quasi-stationary system, leading to the prolonged intense precipitation observed in the Okazaki heavy rainfall event.

著者

坪木 和久 藤吉 康志 若濱 五郎

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.67, no.6, pp.985-999, 1989 (Released:2007-10-19)

参考文献数

30

被引用文献数

14 19

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本研究は、主に一台のドップラーレーダーを用いて、1986年1月20日、石狩平野を南西方向に通過した寒冷前線型の収束雲の運動学的構造とレーダーエコー構造を調べたものである。40kmの幅を持つ収束雲の移動は陸風前線の進行と一致した。陸風前線の形と力学的構造は室内実験の密度流に類似していた。1-2kmの波長を持つケルビン-ヘルムホルツ不安定波が、陸風と北西風の境界に沿って観測された。寒冷前線型では、温暖前線型より強い下層収束とその結果生じた上昇流が前線の前方に存在した。一方、温暖前線型ではみられなかった明瞭な下降流が、前線の後方に存在した。また、このメソスケールの鉛直循環(~15km)の他に、温暖前線と同様な小スケールの循環(~6km)がみられた。前線の前方では上昇流によって対流性エコーが発達し、後方では下降流のためエコーは急速に衰弱する。上昇流は対流不安定層内で最大となることから、下層収束と対流不安定層の存在が、収束雲の発達に重要であると考えられた。

著者

LIU Yonglin TANG Guoping WU Liqiao WU Yuzhen YANG Muzhen

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2019-027, (Released:2018-12-31)

被引用文献数

3

---

Recent climate warming and rapid urban development in the Pearl River Delta (PRD) of China exerted great impacts on the reference evapotranspiration (RET), which in turn affects the management of water resources and the quality of urban environment. The objectives of this study are to examine (i) the temporal variability of RET in PRD, and (ii) the underlying causes responsible for the temporal variation in RET across space inside the PRD. The results indicate that: (1) The RET in PRD had an overall increasing trend caused by the increase of construction land during 1960-2016. (2) The increase of surface albedo caused by land cover conversion from woodland to grassland played an important role in the noticeable decline of RET in Guangzhou and Zengcheng. (3) The dominant factors triggering RET variation varied across space in PRD. In detail, the decline of sunshine duration decreasing Rn, and the decline of wind speed weakening energy exchange, were the dominant factors in decreasing RET in Guangzhou and Zengcheng. In contrast, daily maximum temperature, daily minimum temperature and relative humidity, which were the factors causing the increase of vapor pressure deficit, were responsible for RET increase in Taishan, Zhongshan and Shenzhen. Overall, our results indicated that RET in PRD exhibited strong spatial heterogeneity due to differences in land use change and climatic conditions. Therefore, the improvement of water resources management and urban environment in PRD should consider the spatial variation and underlying forces of RET changes.

著者

FUDEYASU Hironori YOSHIDA Ryuji

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2019-025, (Released:2018-12-13)

被引用文献数

9

---

This study examined the statistical characteristics of tropical cyclones (TCs) for which the cyclogenesis (TCG) process was modulated by upper tropospheric cold lows (UCLs) over the western North Pacific (WNP) during the 38 years from 1979 to 2016. Among the 965 TCs, 90 (9 %, 2.4 per year) were defined as having TCG influenced by UCLs in the northwest quadrant of the TC region (UL-TCs). Most UL-TCs occurred in the summer, with large variability in the annual occurrence rate of UL-TCs during June to October, ranging from 0 to approximately 30 %. The annual variation was related to the activity of the Tibetan high and the summer temperature anomaly over Japan. The extremely hot summer of 2016 was partly enhanced by the intense Tibetan high, when 4 UL-TCs also occurred. The average location of UL-TCs at the time of TCG and tropical storm formation (TSF) was significantly farther to the north than the average location of TCs not formed under the influence of UCL (N-UL-TCs). Many UL-TCs occurred in lower tropospheric environments associated with the shear line or confluence regions. The UL-TCs tended to move northward, and the occurrence rate of UL-TCs that made landfall in Japan was approximately double that of other countries. The atmospheric environmental parameters around UL-TCs at the time of TCG were more favorable for the development of TCs than those around N-UL-TCs. In contrast, the atmospheric and oceanic environmental parameters around UL-TCs at the time of TSF were less favorable for the development of TSs, such that UL-TCs tended to remain at weak in intensity.

著者

Eric A. Smith Alberto Mugnai

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.67, no.5, pp.739-755, 1989 (Released:2007-10-19)

参考文献数

20

被引用文献数

9 17

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鉛直方向と角度について細かくとったマイクロ波の平行放射伝達モデルを用いて、EHF/SHFスペクトル領域にわたる数個の周波数での宇宙空間へ放射されるマイクロ波の伝達に対して、時間に依存して変わる雲の微物理構造の影響を調べるために、雲モデルのシミュレーションとともに、一連の数値実験を行なった。本研究の全般的な目的は、宇宙プラットホームから多チャンネル受動型マイクロ波を利用して降水を推定する技術に介在する物理を詳細に調べることにある。本論文は、先に発表した感度試験研究(Mugnaiand Smith,1988;Smith and Mugnai,1988)の続きである。発達するモデル雨雲における受動型マイクロ波の輝度温度に対する大きな氷粒子の効果を、EHF/SHFスペクトル域の10個の周波数で調べた。固い氷結モード及び低密度の氷結モードの両方に対して、それぞれ三つの雲モデルを考慮した。結果は、10.7GHz と 231GHz の問の周波域が、様々の雲モデルや氷結モードに異なって応答することを、はっきり示している。個々の雲層や降水層の輝度温度に果たす寄与を鉛直方向に分離するために我々が導入した、周波数に依存して鉛直に分布する一般化射出/散乱加重関数は、大気上端での輝度温度の強さに強く関与している特定の層を同定するのに、どのように利用できるかを示した。その一般化加重関数は、それ自身における散乱項の相対的強さを示す散乱関数め寄与率とも結びついている。このことは、輝度温度が個々の層における降水粒子によっていかに加減されるか、をよく理解する助けになる。この研究のもう一つの顕著な成果は、中間または高周波数(37GHz以上)に対する、混合相の存在の重要性を明らかにしたこと、及び85GHzでの氷結モードの影響を定量的に示したことである。更に、ある一定の全液体水分量に対しては、雲の鉛直スケールが、実際の観測と合う輝度温度を与える上での、主な支配的要因であることが示された。この結果は、北部アラバマでの1986年の COHMEX 実験における、航空機搭載の2チャンネルマイクロ波放射計による激しい雷雲の観測の実例解析に基づいている。

著者

Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2018-027, (Released:2018-10-12)

被引用文献数

35

---

An extreme, damaging rainfall occurred in northern Kyushu in July 2017. Whether such an extreme rainfall is quantitatively captured by numerical models is a challenging issue. We investigate the influences of terrain representation in simulating a stationary convective system and the resulting heavy rainfall for this case by conducting a series of 167-m-resolution numerical experiments. By employing a high-resolution elevation dataset as well as a double-moment cloud microphysics scheme, the control experiment successfully reproduced the stationary, linear-shaped convective system and the associated heavy rainfall. When the model terrain was created by a coarser-resolution elevation dataset, the 167-m-resolution experiment underestimated the accumulated rainfall, because of discretely developing convection and weaker intensities of the rainfall.These impacts of the terrain representation were confirmed to be robust through conducting another experiments with a different microphysics scheme. The representation of model terrains is critically important in simulating stationary convective systems and quantitatively the resulting heavy rainfall.

著者

CHEN Yaodeng WANG Jia GAO Yufang CHEN Xiaomeng WANG Hongli HUANG Xiang-Yu

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2018-048, (Released:2018-06-22)

被引用文献数

3

---

Background error covariance (BEC) is one of the key components in the data assimilation systems for numerical weather prediction. Recently, a scheme of using an inhomogeneous and anisotropic BEC estimated from historical forecast error samples has been tested by employing the extended alpha control variable approach (BEC-CVA) in the framework of the Variational Data Assimilation system for the Weather Research and Forecasting model (WRFDA). In this paper, the BEC-CVA approach is further examined by conducting single observation assimilation experiments and continuously cycling data assimilation and forecasting experiments covering a 3-weeks period. Moreover, additional benefits of using a blending approach (BEC-BLD), which combines a static, homogeneous BEC with an inhomogeneous and anisotropic BEC, are also assessed. Single observation experiments indicate that the noises in the increments in BEC-CVA can be somehow reduced by using BEC-BLD, while the inhomogeneous and multivariable correlations from the BEC-CVA are still taken into account. The impact of BEC-CVA and BEC-BLD on short-term weather forecasts is compared with three-dimensional variational data assimilation scheme (3DVar), and compared with the hybrid ensemble transform Kalman filter and 3DVar (ETKF-3DVar) in WRFDA also. Results show that the BEC-CVA and BEC-BLD outperform the use of 3DVar. It is shown that BEC-CVA and BEC-BLD underperform ETKF-3DVar as expected, however the computational cost of BEC-CVA and BEC-BLD is considerably less expensive since no ensemble forecasts are required.

著者

松本 誠一

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.45, no.1, pp.53-63, 1967 (Released:2008-05-27)

参考文献数

19

被引用文献数

6 14

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北陸地方に設定した細かい観測網による高層観測資料に基ずき,熱および水収支を1963,1964および1965年の3ケ年分の特別観測期間につき比較した。水蒸気の収束量はこの3冬とも殆んど同じ値を示しているが,降水量は年々非常に変っている。海面からの蒸発および対流輸送量の違いはかなりあるけれども,降水の変動には主として凝結した水分の輸送が関係している。6時間間隔の水蒸気輸入量を領域内の6時間降水量と比較すると,風下側の観測点の降水量とよい関係があることが分る。平均流束による発散で計算すると顕熱増加量は潜熱減少量のほぼ2倍になることが示される.この関係は観測網の大きさに関係なく,とくに雲層内でよく成立っている。差引き過剰の熱エネルギーは対流活動により輸送されているものと考えられる。強い降雪が観測されるときには対流活動が盛んで,海面から補給される熱エネルギーよりも多い熱エネルギーを雲層に輸送していることが示唆される。本研究は北陸豪雪特別研究の一環としてなされたものである。

著者

柳井 連雄

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.39, no.5, pp.282-309, 1961-12-28 (Released:2007-10-19)

参考文献数

98

被引用文献数

17 33

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台風の発生機構を力学的に説明することを試みた。台風の発生とは,既存の大規模な低緯度擾乱が激しい自由対流に転化することであると考える。第一章で大気中に起る種々の自由対流,強制対流について一般的考察を行なつた。特に堰形渦中の自由子午面須環の発達速度を不安定成層,安定成層の各々の場合につき摂動の水平スケールの関数として論じた。台風のような大きいスケールを持つ擾乱の発達を説明し得るものは安定成層中の傾圧性(すなわちradialな温度差)による力学的不安定であつて,これはFultzやHideによつて行なわれたdishpan実験中にみられ,Kuoによつて理論的に説明されている激しいHadley型対流の機構と本質的に同じである。第二章では実際の台風発生過程を三段階に分け,各々のstageにおいて支配的な機構を説明した。第一は偏東風波に伴う力学的強制上昇流の維持,第二はその強化と,その中での積雲対流の誘発,潜熱放出による中心部の温暖化,第三が形成された水平温度差が臨界値を越したときの激しいHadley型自由対流への転化である。要するに凝結熱は発生期においても台風の一次的垂直循環の直接的原因ではなく,それはwarm coreの形成,維持を通して重要なのである。

著者

KHATRI Pradeep HAYASAKA Tadahiro IWABUCHI Hironobu TAKAMURA Tamio IRIE Hitoshi NAKAJIMA Takashi Y.

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2018-036, (Released:2018-04-09)

被引用文献数

9

---

The present study implements long-term surface observed radiation data (pyranometer observed global flux and sky radiometer observed spectral zenith transmittance data) of multiple SKYNET sites to validate water cloud optical properties (cloud optical depth COD and effective radius Re) observed from space by MODIS onboard TERRA and AQUA satellites and AHI onboard Himawari-8 satellite. Despite some degrees of differences in COD and Re between MODIS and AHI, they both showed common features when validated using surface based global flux data as well as cloud properties retrieved from sky radiometer observed zenith transmittance data. In general, CODs from both satellite sensors are found to overestimated when clouds are optically thin. Among a number of factors (spatial and temporal variations of cloud, sensor and solar zenith angles), the solar zenith angle (SZA) is found to have an impact on COD difference between reflectance based satellite sensor and transmittance based sky radiometer. The Re values from the sky radiometer and satellite sensor are generally poorly correlated. The difference in Re between the sky radiometer and satellite sensor is negatively correlated with COD difference between them, which is likely due to the inherent influence of Re retrieval precision on COD retrieval and vice versa in transmittance based sky radiometer.

著者

OKUYAMA Arata TAKAHASHI Masaya DATE Kenji HOSAKA Keita MURATA Hidehiko TABATA Tasuku YOSHINO Ryoko

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2018-033, (Released:2018-03-30)

被引用文献数

23

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The new geostationary meteorological satellite of the Japan Meteorological Agency (JMA), Himawari-8, entered operation on 7 July 2015. Himawari-8 features the new 16-band Advanced Himawari Imager (AHI), whose spatial resolution and observation frequency are improved over those of its predecessor MTSAT-series satellites. These improvements will bring unprecedented levels of performance in nowcasting services and short-range weather forecasting systems. In view of the essential nature of navigation and radiometric calibration in fully leveraging the imager’s potential, this study reports on the current status of calibration for the AHI. Image navigation is accurate to within 1 km, and band-to-band co-registration has also been validated. Infrared-band calibration is accurate to within 0.2 K with no significant diurnal variation, and is being validated using an approach developed under the GSICS framework. Validation approaches are currently being tested for the visible and near-infrared bands. Two such approaches were compared and found to produce largely consistent results.

著者

Wataru Mashiko Hiroshi Niino

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.135-139, 2017 (Released:2017-07-31)

参考文献数

26

被引用文献数

6

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A super high-resolution simulation of the 6 May 2012 Tsukuba supercell tornado with a horizontal grid spacing of 10 m is conducted to investigate its fine-scale structure under realistic environmental conditions including surface friction. The simulated tornado repeatedly exhibits evolutions from one-cell to two-cell vortex, and subsequently to a multiple-vortex structure, where the vortex structure is sensitive to a swirl ratio. Subvortices in the multiple-vortex structure are located on the immediate inside of the radius of the maximum tangential wind speed, and cyclonically rotate around the tornado center with a slower speed less than half of the maximum tangential wind speed. The subvortices have a feature of a suction vortex accompanied by strong horizontal convergence and strong updraft near the surface. Although a superposition of the swirling winds associated with the subvortices and the parent tornado vortex causes locally intensified winds, the maximum horizontal and upward winds over the tornado's lifetime occur at the stage of shrinking of the vortex radius right before a transition to a multiple-vortex structure.

著者

Hongli WANG Linjing QIU Xiaoning XIE Zhiyuan WANG Xiaodong LIU

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.96, no.4, pp.391-403, 2018 (Released:2018-08-02)

参考文献数

27

被引用文献数

2

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The climate variability in monsoon and arid regions attributable to dynamic vegetation is investigated using NCAR's Community Earth System Model with the Dynamic Global Vegetation Model. Two present climate simulations, one using dynamics and the other using fixed vegetation cover, are carried out. A comparative analysis of the two simulations reveals that the climate in monsoon and arid regions exhibits different responses to dynamic vegetation. On the hemispheric scale, precipitation mainly increases in the Northern Hemisphere and decreases in the Southern Hemisphere in response to dynamic vegetation, while the surface temperature exhibits a consistent decrease. On the regional scale, precipitation decreases caused by dynamic vegetation are the main trend in monsoon regions except for the Asian monsoon region, while precipitation responses to vegetation change are weak in arid regions relative to monsoon regions. The surface temperature increases significantly because of dynamic vegetation only in the boreal winter Asian monsoon region, while the rest of the monsoon and arid regions mainly exhibit reduced surface temperatures. Therefore, the climate variability in the Asian monsoon region is clearly different from the other regions. Further analysis shows that dynamic vegetation can modulate variations in the east–west sea-level pressure gradient and lower-level meridional winds in East Asia, and it can strengthen (weaken) the East Asian summer (winter) monsoon. Mechanistic analysis reveals that the difference in hemispheric and regional climate variations may be due to changes in the dynamic vegetation-induced moisture flux and net surface radiative forcing.

著者

ZHUGE Xiaoyong ZOU Xiaolei

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2018-041, (Released:2018-04-13)

被引用文献数

19

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Convective initiation (CI) nowcasting often has a low probability of detection (POD) and a high false-alarm ratio (FAR) at sub-tropical regions where the warm-rain processes often occur. Using the high spatial- and temporal-resolution and multi-spectral data from the Advanced Himawari Imager (AHI) on board Japanese new-generation geostationary satellite Himawari-8, a stand-alone CI nowcasting algorithm is developed in this study. The AHI-based CI algorithm utilizes the reflectance observations from channels 1 (0.47 μm) and 7 (3.9 μm), brightness temperature observations from infrared window channel 13 (10.4 μm), the dual-spectral differences between channels 10 (7.3 μm) and 13, 13 and 15 (12.4 μm), as well as a tri-spectral combination of channels 11, 15 and 13, as CI predictors without relying on any dynamic ancillary data (e.g., cloud type and atmospheric motion vector products). The proposed AHI-based algorithm is applied to CI cases over Fujian province in the Southeastern China. When validated by S-band radar observations, the CI algorithm produced a POD as high as 93.33 %, and a FAR as low as 33.33 % for a CI case day that occurred on 1 August 2015 over Northern Fujian. For over 216 CI events that occurred in a three-month period from July to September 2015, the CI nowcasting lead time has a mean value of ~64 minutes, with a longest lead time over 120 minutes. It is suggested that false-alarm nowcasts that occur in the presence of capping inversion require further investigation and algorithm enhancements.

著者

播磨屋 敏生

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.46, no.4, pp.272-279, 1968 (Released:2008-05-27)

参考文献数

13

被引用文献数

2 5

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かぎ状絹雲をmother-cloudからの降水のtrai1によるものと考えて,その特異な形を決める因子を観測値に基づいた温度,湿度,風速の垂直分布のもとで数値計算により調べた.計算の結果から次の事が結論される.かぎ状絹雲の形は,降水粒子の質量および風の垂直シャーに非常に依存する.また軸比が非常に大きい針状結晶を除いては,降水粒子の形にはあまり依存しない.

著者

Xi CAO Renguang WU

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.96, no.4, pp.317-336, 2018 (Released:2018-07-27)

参考文献数

43

被引用文献数

7

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The present study compares contributions of different environmental factors to the tropical cyclone (TC) genesis over the western North Pacific (WNP) during 2015 and 2016. A local instantaneous view of conditions for the TC genesis is adopted in the present study, which is distinct from the previous view of large-scale temporal averaged conditions. The present study also distinguishes the contributions of three time scale variations (synoptic, intraseasonal, and interannual) of a number of factors. Common to 2015 and 2016, the positive contribution of lower-level vorticity and upward motion to the TC genesis is mainly from the intraseasonal and synoptic components; the contribution of the barotropic energy conversion to the development of synoptic disturbances is larger from climatological mean winds and intraseasonal wind variations than from interannual wind variations; all three time scale variations of mid-level specific humidity contribute positively to the TC genesis; the barotropic energy conversion from climatological mean winds is due to the terms in relation to the meridional shear and zonal convergence of zonal wind. In comparison, the positive contribution of lower-level vorticity and mid-level specific humidity is larger in 2015 than in 2016 on all the three time scales; the contribution of the barotropic energy conversion in relation to the meridional shear of interannual variations of zonal wind and the zonal convergence of intraseasonal variations of zonal wind are larger in 2015 than in 2016; the vertical wind shear on all the three time scales and the sea surface temperature on the interannual time scale have a larger positive contribution to the TC genesis in 2016 than in 2015.

著者

Kayo Ide Philippe Courtier Michael Ghil Andrew C. Lorenc

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.75, no.1B, pp.181-189, 1997-03-25 (Released:2008-01-31)

参考文献数

32

被引用文献数

286 622

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The need for unified notation in atmospheric and oceanic data assimilation arises from the field's rapid theoretical expansion and the desire to translate it into practical applications. Self-consistent notation is proposed that bridges sequential and variational methods, on the one hand, and operational usage, on the other. Over various other mottoes for this risky endeavor, the authors selected: "When I use a word, " Humpty Dumpty said, in rather a scornful voice tone, "it means just what I choose it to mean - neither more more less. "Lewis Carroll, 1871.