著者

Xue-Song ZHU Hui 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

vol.97, no.1, pp.153-173, 2019 (Released:2019-02-14)

参考文献数

53

被引用文献数

6

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Using brightness temperature data from passive microwave satellite imagery, this study examines tropical cyclones (TCs) with concentric eyewall (CE) in the western North Pacific between 1997 and 2011. The identified CEs are divided into two types according to the characteristics of the eyewall replacement cycle (ERC) in the microwave imagery: a CE with a typical ERC (T-ERC) and a CE without an ERC (N-ERC). It is indicated that 88% T-ERCs reach peak intensity near (0.2 h after on average) CE formation, whereas 90% N-ERCs reach peak intensity prior to (22.0 h on average) CE formation. In general, N-ERCs tend to occur when there are strong interactions between the environment and the CE, whereas T-ERCs occur in a relatively quiet environment. The three-dimensional conceptual models of the environmental configurations for both CE types are proposed. Specifically, N-ERCs are accompanied by stronger southwesterly and southeasterly inflows, active low-level trough, and stronger subtropical high (SH) and South Asia high (SAH), compared with T-ERCs. For N-ERCs, the stronger inflows may bring in a large amount of moisture, and the active low-level trough may result in a large vertical wind shear (VWS). The stronger SH and SAH may contribute to changes in the intensity and direction of the VWS for N-ERCs, and hence trigger the development of local convection in the outer eyewall. The asymmetries in the convection of the outer eyewall may weaken the ability to cut off the radial inflow to the inner eyewall. Consequently, N-ERCs fail to finish the ERC and weaken rapidly in intensity, even though the moisture remains sufficient after CE formation.

著者

FUKUSHIMA Hirokazu YAZAKI Tomotsugu HIROTA Tomoyoshi IWATA Yukiyoshi WAJIMA Atsushi YOKOTA Ayumi

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.2019-005, (Released:2018-10-29)

被引用文献数

5

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There is an increasing need for accurate winter agrometeorological forecasts, which is facilitated by a better understanding of the evolution process of nighttime air temperature distribution. However, studies on how air temperature distributions evolve in mesoscale plains have been limited. To clarify how the low temperatures in winter nights form, we analyzed the effects of topography and boundary-layer wind on the temperature distribution of the Tokachi region for a winter night using numerical simulations by the Japan Meteorological Agency Nonhydrostatic Model (JMA-NHM)with horizontal grid spacing of 2 and 5 km. We also analyzed vertical profiles of boundary-layer atmospheric conditions. The results show that, although boundary-layer wind is expected to affect the temperature distribution over the entire Tokachi region, the effects were generally confined to the northwestern part. Widespread effects over the Tokachi region were found only under strong wind conditions. We found that the mountain pass in the northwestern part of the Tokachi region is an important wind path, and the downslope winds as well as the sensible heat transfer by turbulent mixing in the boundary layer also was important in the evolution of the air temperature distribution. On the night we considered, a moderate boundary-layer wind was maintained throughout the night, but the surface wind speed decreased from the northern and southern parts of the Tokachi region; this can be attributed to the development of an inversion layer. A drainage flow was observed to originate from the southern part of the Tokachi Plain, reaching the central part of the Tokachi region in the night. We find that radiative cooling and sensible heat transfer by turbulent mixing in the surface layer do not adequately explain the temporal change in observed surface air temperatures. The development of an inversion layer and katabatic drainage flow drastically change the temperature distribution, despite a moderately strong wind condition in the boundary layer.

著者

KUO Kuan-Ting WU Chien-Ming

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.2019-031, (Released:2019-02-02)

被引用文献数

11

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In this study, the mechanism for precipitation hotspots (PHs) of locally developed afternoon thunderstorms in the Taipei Basin is investigated using a three-dimensional Vector Vorticity equation cloud resolving Model (VVM) with an idealized topography and surface properties. A 500-m horizontal grid resolution is used in all experiments. The results show that the local circulation is a key for PHs at the south of the Taipei Basin. The two valleys guide background southwesterly flow along with the sea breezes to penetrate into the basin. The urban heat island effect enhances the sea breeze convergence at the south of the basin and produces strong convection there. Interactions between cold pools generated by the convection and the sea breezes produce northward propagating new convective cells. Besides, the background wind direction is important in determining the location of sea breeze convergence. If the background wind direction changes from westerly to west-northwesterly, there might be no precipitation at all in the basin. This study suggests that the idealized experiments also provide a useful framework for studying the impacts of future climate change on the PHs in the Taipei Basin by applying the pseudo-global warming approach.

著者

Akio KITOH Hirokazu ENDO

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.97, no.1, pp.141-152, 2019 (Released:2019-02-06)

参考文献数

40

被引用文献数

22

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Future changes in precipitation extremes and role of tropical cyclones are investigated through a large ensemble experiment, considering 6,000 years for the present and 5,400 years under +4 K warming, using a 60-km mesh Meteorological Research Institute atmospheric general circulation model version 3.2. As in the previous findings of the authors, the annual maximum 1-day precipitation total (Rx1d) is projected to increase in the warmer world in the future almost globally, except in the western North Pacific where a projected decrease of tropical cyclone frequency results in only small change or even reduction of Rx1d. Furthermore, a large ensemble size enables us to investigate the changes in the tails of the Rx1d distribution. It is found that 90- and 99-percentile values of the Rx1d associated with tropical cyclones will increase in a region extending from Hawaii to the south of Japan. In this region, the interannual variability of the Rx1d associated with tropical cyclones is also projected to increase, implying an increasing risk of rare heavier rainfall events because of global warming.

著者

Wataru MASHIKO

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.97, no.1, pp.39-54, 2019 (Released:2019-02-07)

参考文献数

41

被引用文献数

1

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In this study, the characteristics of wind gusts in Japan in the period from 2002 to 2017 were examined using surface meteorological data recorded at 151 weather observatories throughout Japan. This study does not focus on particular phenomena, such as tornadoes and downbursts, which cause wind gusts. A wind gust is defined on the basis of the gust factor and the amount of increase and decrease of the 3-s mean wind speed from the 10-min mean wind speed. A total of 3,531 events were detected as wind gusts. The frequency of wind gusts with more than 25 m s−1 averaged across all observatories is 0.97 per year, which is four or five orders of magnitude higher than the tornado encounter probability in Japan. The frequency of wind gusts in the coastal region is approximately three times higher than that in the inland area. Wind gusts occur most frequently in September and least frequently in June. Wind gusts have high activities during daytime, especially in the afternoon. Approximately half of the events are the typhoon-associated wind gusts (WGTYs), which occurred within a radius of 800 km from the typhoon center. Most of the WGTYs occur from August to October. Approximately half of the WGTYs occur in the right-front quadrant of a typhoon with respect to the typhoon motion. The frequency of WGTYs is high in western Japan, whereas the northern and eastern parts of Japan are characterized by a high frequency of wind gusts without a typhoon. In addition, persistent strong winds, which meet the same conditions as wind gusts but without a rapid decrease in the wind speed, were investigated. The frequency of such strong winds is high on the Japan Sea coast, especially in December. The effects of the observational environment on the frequency of wind gusts were also discussed.

著者

真木 雅之 播磨 屋敏生

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

vol.66, no.4, pp.581-597, 1988

被引用文献数

16

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盆地において,まわりの山地斜面からの冷気の移流•堆積が地表面の夜間冷却量に及ぼす効果を1次元の数値モデルを用いて調べた。数値モデルは冷気の移流•堆積による大気層の冷却を熱収支的な立場から考慮したものである。計算結果によれば,例えば,盆地の深さが500m の場合,風の弱い快晴の夜間に,盆地底での夜間冷却量は平坦地に比べ約15%(冬期)から約25%(夏期)大きくなり,山頂や丘陵頂部に比べ約40%(冬期)から約90%(夏期)大きくなる。これは,盆地のようにまわりを山で囲まれたところでは山地斜面からの冷気が盆地中央部上空へ移流•堆積するために,盆地底での下向きの大気放射量が小さくなり,地表面の放射冷却を強めるためである。この冷気の移流•堆積の効果は深い盆地ほど顕著である。移流による大気層の冷却が盆地に比べて小さい山麓の地表面冷却量は盆地に比べて小さくなるが,平坦地に比べて約10%(冬期)から約15%(夏期)大きく,山頂や丘陵頂部に比べて約30%(冬期)から約75%(夏期)大きくなる、計算された結果は AMeDAS で観測された結果と比較して妥当なものであった。

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

菊地 勝弘

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

vol.42, no.6, pp.341-353, 1964

被引用文献数

2

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北海道石狩湾々上,特に沿岸付近に冬期間早朝しばしば雲頂20~30mめ層状の雲が発生した。これ等の雲を手稲山頂から35ミリカメラおよび16ミリムービーカメラで一定時間毎に撮影し,観測した。その結果,はじめ層状に発生したこれ等の雲は日の出後時間と共に上昇し,雲頂200m位でセル状となり,規則正しい列状に配列し,10時前後にいずれも消滅した。解析の結果,これ等の雲は夜間の強い輻射冷却により石狩平野上にできた寒気が,比較的暖かい石狩湾上に吹出し,垂直混合により湾上の暖気が凝結してできたものと考えられる。日の出後寒気の吹出しが弱まり,逆転層の上昇とともに,これ等の雲は上昇し,セル状となりその高度のwind shearによって列状に配列したものであろう。この論文ではこの雲を"Coastal Cloud"と名付けた。<br>観測されたCoastal Cloudsはsmall scaleのもので降水現象を伴わなかったが,もし同様な過程でlarge scaleに生ずるならば,前線や山岳効果がなくても降水をもたらすことが十分期待される。

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

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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

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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

高橋 劭

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

vol.55, no.1, pp.121-129, 1977

被引用文献数

6

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ハワイ島の雨を逆転層の高さ,強度に関係させて分類することをこころみた。貿易風の強い8月の場合がこの論文ではくわしく解析された。雨は逆転層が低い時に見られる早朝と夕方のシャワー(海&bull;陸風に左右される),逆転層の高い時に見られる日中の強い雨,逆転層が2層あるときの地雨に大別された,又この逆転層が上層のcyclonic ce11の動きと密接な関係があることもわかった。<br>Front systemの影響をうけるハワイの冬の雨との比較で空中電場に強い差が見られた。氷晶の存在がその原因であろう。

著者

櫻庭 信一

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

vol.22, no.9, pp.303-304, 1946

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

本多 弘吉

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

vol.8, no.10, pp.361-363, 1930

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

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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。