著者

XIN Xiaoge WEI Min LI Qingquan ZHOU Wei LUO Yong ZHAO Zongci

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.2019-043, (Released:2019-04-01)

被引用文献数

3

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Two sets of decadal prediction experiments were performed with Beijing Climate Center climate system model version 1.1 (BCC-CSM1.1) with different initialization strategies. One experiment is relaxing modeled ocean temperature to the Simple Ocean Data Assimilation (SODA) reanalysis data (SODAInit). In the other (EnOI_HadInit) experiment, the modeled ocean temperature were relaxed toward the assimilated ocean data, which were generated by assimilating sea surface temperature (SST) of the Hadley Centre Sea Ice and Sea Surface Temperature (HadISST) data to the ocean model of BCC-CSM1.1 using Ensemble Optimum Interpolation (EnOI) method. Comparisons between EnOI_HadInit and SODAInit hindcasts show that EnOI_HadInit is more skillful in predicting SST over the North Pacific, the southern Indian Ocean, and the North Atlantic. Improved prediction skill is also found for surface air temperature (SAT) over South Europe, North Africa, and Greenland, which is associated with the skillful prediction of the Atlantic multi-decadal oscillation in EnOI_HadInit. EnOI_HadInit and SODAInit are both skillful in predicting East Asian SAT, which is related to their skillful predictions of the tropical western Pacific SST. The result indicates that assimilated data generated by the ocean model of BCC-CSM1.1 with EnOI assimilation provide better initial conditions than SODA reanalysis data for the decadal predictions of BCC-CSM1.1.

著者

LIM Jaechan PARK Hyung-Min

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.2019-041, (Released:2019-03-19)

被引用文献数

1

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In this paper, we propose an H-infinity (H∞) filtering approach for the prediction of bias in post-processing of model outputs and past measurements. This method adopts minimax strategy that is a solution for zero-sum games. The proposed H∞ filtering approach minimizes maximum possible errors whereas a recently common approach that adopts the Kalman filtering (KF) minimizes the mean square errors. The proposed approach does not need the information of noise statistics unlike the method based on the KF, while training process is required. We show that the proposed approach outperforms the method based on the KF in experiments by applying real weather data in Korea.

著者

KUO Tzu-Hsien MURAKAMI Masataka TAJIRI Takuya ORIKASA Narihiro

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.2019-032, (Released:2019-02-02)

被引用文献数

3

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Aluminum oxide (Al2O3) and iron oxide (Fe2O3) particles have been observed not only in industrial areas and their surroundings but also in natural atmospheric environments. These types of aerosols can influence aerosol–cloud interactions. In this study, physico-chemical properties, such as size distribution and ability to act as cloud condensation nuclei (CCN) as well as ice nucleating particles (INPs), of surrogates of ambient Al2O3 and Fe2O3 particles were investigated using a CCN counter, the Meteorological Research Institute’s (MRI’s) cloud simulation chamber, the MRI’s continuous flow diffusion chamber-type ice nucleus counter, and an array of aerosol instruments. The results indicated that their hygroscopicity parameter (κ-value) ranged from 0.01 to 0.03. This range is compatible with that of surrogates of mineral dust particles and is smaller than typical κ-values of atmospheric aerosols. On the other hand, based on their ice nucleation active surface site (INAS) densities, these materials may act as effective INPs via immersion freezing (i.e., ice nucleation triggered by particles immersed in water droplets). In the cloud chamber experiments, Al2O3 and Fe2O3 particles continuously nucleated ice crystals at temperatures < −14°C and < −20°C, respectively. This result indicates that the Al2O3 particles were better INPs than the Fe2O3 particles. Moreover, the INAS density of the Al2O3 particles was comparable to that of natural ambient dust.

著者

TAUVALE Luteru TSUBOKI Kazuhisa

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.2019-042, (Released:2019-04-01)

被引用文献数

7

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Geographic and meteorological characteristics of 479 tropical cyclones (TCs) in a study domain in the Southwest Pacific (defined by 135°E - 120°W and 5°S - 65°S) over the past 48 TC seasons from 1969–1970 to 2016–2017 were examined using the latest Southwest Pacific Enhanced Archive of Tropical Cyclones dataset. Examined metrics include the geographic distributions of TCs, numbers, intensity, length in days (TC days), accumulated cyclone energy (ACE), and power dissipation index (PDI). The results show increasing TC activities in the western, northwestern, northern and central subdomains of the nine subdomains in the study domain. The average latitudes of TC genesis and TC maximum intensity remained almost unchanged. Most of TCs took southward to southeastward paths, and the majority attained their maximum intensities in the western and central parts of the study domain. The annual number of TCs and TC days decreased over the study period, the numbers of stronger TCs slightly increased whereas stronger TC days increased. The highest annual lifetime-maximum intensity and average annual lifetime-maximum intensity also increased. The highest annual maximum intensification rates did not change much over the study period, nor did ACE and PDI. The results show correlations between highest annual lifetime-maximum intensity to the variations of average sea surface temperature (SST) as well as correlations between TC days to the variations of average SST in the region.

著者

HIROSE Hitoshi SHIGE Shoichi YAMAMOTO Munehisa K. HIGUCHI Atsushi

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.2019-040, (Released:2019-03-15)

被引用文献数

23

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We introduce a novel rainfall estimation algorithm with a random-forest machine-learning method only from Infrared (IR) observations. As training data, we use nine-band brightness temperature (BT) observations obtained from IR radiometers on the third-generation geostationary meteorological satellite (GEO) Himawari-8 and precipitation radar observations from the Global Precipitation Measurement core observatory. The Himawari-8 Rainfall estimation Algorithm (HRA) enables us to estimate rain rate with high spatial and temporal resolution (i.e., 0.04° every 10 min), covering the entire Himawari-8 observation area (i.e., 85°E–155°W, 60°S–60°N) based solely on satellite observations. We conducted a case analysis of the Kanto–Tohoku heavy rainfall event to compare rainfall estimation results of HRA and the near-real-time version of the Global Satellite Mapping of Precipitation (GSMaP_NRT), which combines global rainfall estimation products with microwave and IR BT observations obtained from satellites. In this case, HRA could estimate heavy rainfall from warm-type precipitating clouds, although GSMaP_NRT could not estimate heavy rainfall when the microwave satellites were unavailable. Further, a statistical analysis showed that the warm-type heavy rain seen in the Asian monsoon region occurred frequently when the BT differences between the 6.9-μm and 7.3-μm of water vapor (WV) bands (ΔT6.9–7.3) were small. Himawari-8 is the first GEO to include the 6.9-μm band which is sensitive to middle-to-upper tropospheric WV. An analysis for the weighting functions of the WV multibands revealed that ΔT6.9–7.3 became small as WV amount in the middle-to-upper troposphere was small and there were optically thick cloud with the cloud top near the middle troposphere. Statistical analyses during boreal summer (August and September 2015 and July 2016) and boreal winter (December 2015 and January and February 2016) indicate that HRA has higher estimation accuracy for heavy rain from warm-type precipitating clouds than a conventional rain estimation method based on only one IR band.

著者

Akiyoshi WADA Hiroshige TSUGUTI Kozo OKAMOTO Naoko SEINO

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.3, pp.553-575, 2019 (Released:2019-06-05)

参考文献数

62

被引用文献数

4

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The September 2015 Kanto-Tohoku heavy rainfall event occurred in a stationary linear convective system between Typhoons Kilo and Etau. We investigated the influence of sea surface temperature (SST) on the local heavy rainfall event using a regional air-sea strongly coupled data assimilation system based on the local ensemble transform Kalman filter (LETKF) and a nonhydrostatic atmosphere model (NHM) coupled with an ocean-surface wave model and a multilayer ocean model with an Advanced Microwave Scanning Radiometer 2 (AMSR2) level 2 (L2) SST product. From the validation of SST analyzed by the coupled data assimilation system with the Japanese geostationary multi-functional transport satellite 2 hourly SST product and in-situ observations at a moored buoy, we demonstrated that the coupled system with the AMSR2 L2 SST led to an improvement in the SST analysis. Based on the verification using radiosonde observations and radar-rain gauge rainfall analysis, the analysis of the lower-atmospheric components was improved by the air-sea coupled NHM-LETKF. The local torrential rainfall event that occurred around 37°N in the Tochigi prefecture was embedded in a stationary linear convective system. The location of the linear convective system corresponded to the synoptic-scale convergence area between the cyclonic circulation associated with Etau and easterly lower-tropospheric winds. Strong southerly winds associated with Etau caused a periodic enhancement of local convection along the convergence area on the upwind side of the linear convective system and resulted in a wave-like train of the total water content around an altitude of 4-8 km on the leeward side. The improvement of SST analysis could not only change the transition of Etau to the extratropical cyclone but also the lower-tropospheric wind field and thereby the location of the stationary linear convective system with embedded local torrential rain.

著者

新野 宏

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.58, no.1, pp.33-51, 1980

被引用文献数

2

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非圧縮で粘性がなく,密度一様な回転流体中で,回転軸に平行な体積力によって作り出された層流ジェットの振舞を線形論によって調べた。体積力はある有限の領域(以下領Aと呼ぶ)に軸対称に分布している。この力は,ある時刻(t*=0)に急に働き始め,その後の変化として<br>1) 無限に続く場合(連続的な力)<br>2) 時刻t*=T*に止む場合(継続時間T*の力)の2通りを考えるものとする。<br>連続的な力に対しては,流れの場は時間と共に回転軸方向に一様になるが,領域A内ではテイラー&bull;プラウドマンの定理が成り立たない為に圧力と接線速度は軸方向に一様にはならない。特に圧力場には,体積力に逆らうような軸方向の圧力傾度が次第に形成される。この圧力傾度は体積力が働き始めてからt*=10.90/fでほとんど定常になることがわかった。(ここでfはコリオリ係数である。)そして,定常状態では圧力傾度力は軸方向には体積力と,半径方向にはコリオリカとつりあっている。<br>継続時間T*の力に対しては,もしT*が10.90/fよりも大きいならば,力が止んだ後の領域A内の運動はT*によらないことがわかった。このような大きな値のT*に対しては,力が止んでからt*'=3.4/fと6.5/fとの間に領域A内に逆流が生ずる。(ここで,t*'=t*-T*である。)この逆流は,体積力が止むまでそれとつり合っていた逆向きの圧力傾度力によって生ずる。やがて,逆流が弱くなった後は,領域A内に周期約2&pi;/fの減衰振動が残る。この論文のモデルは,回転流体中の乱流ジェットの室内実験で見つかった逆流を説明する為に作られた線形論(新野,1978)をより洗練した形にしたものである。

著者

SHIN Uju LEE Tae-Young PARK Sang-Hun

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.2019-036, (Released:2019-02-19)

被引用文献数

10

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An investigation has been carried out using rainfall observation data, National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) analysis and forecast data to explain the environment and processes that lead to heavy rainfall in the early morning over the Korean peninsula during episodes of cloud clusters (CCs) associated with mesoscale troughs (CCMTs). For this study, nine episodes with maximum hourly rainfall amount in the early morning (i.e., 0300–0900 LST) are selected from seventeen heavy-rainfall episodes associated with CCMTs during 2001–2011. Case studies on two episodes have revealed that, for both episodes, 1) a low-level trough develops over eastern China and its coastal area during the daytime; 2) the strong southwesterly band (SWB; an area with wind speeds > 12.5 m s-1) on the pressure level 925 hPa over the East China Sea, which is located southeast of the trough, strengthens and expands at nighttime toward the southwestern Korean peninsula; 3) the SWB supplies large amount of moisture and increases convective instability over the southwestern Korean peninsula with a convection trigger mechanism (i.e., strong horizontal convergence); and 4) heavy rainfall occurs in the early morning over the southwestern Korean peninsula, where the exit region of the SWB is located. A mechanism for the SWB growth is presented. Furthermore, generality of the major results from the two case studies is verified using the results obtained for the composite fields of the 9 CCMT episodes.

著者

SAUNDERS Peter YU Yafan PU Zhaoxia

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.2019-030, (Released:2019-01-25)

被引用文献数

3

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Hurricane Joaquin, a notable hurricane over the Atlantic Ocean in 2015, is studied with emphasis on its unique hairpin turn that occurred between 2100 UTC 1 October and 0600 UTC 2 October 2015. A series of mesoscale high-resolution numerical simulations is performed with an advanced research version of the Weather Research and Forecasting (WRF) model. The sensitivity of numerical simulations to different cumulus, boundary layer, and microphysical parameterization schemes is examined to investigate the most relevant processes influencing the track evolution of Hurricane Joaquin. It is found that the numerical simulation of Hurricane Joaquin’s track is highly sensitive to the choice of cumulus scheme. Large-scale environmental conditions and hurricane inner-core structures are diagnosed. Results indicate that middle- to upper-level steering flows are crucial in influencing Joaquin’s track. Further investigation of the large-scale environment (e.g., middle- and upper-level trough, blocking high, thermal distribution, etc.) shows that middle-level blocking high plays an important role in Joaquin’s movement. The structure of the hurricane core region, including the vertical extent of diabatic heating, vertical velocity, and relative humidity, could also play an important role. Specifically, the asymmetry and local absolute vorticity tendency over the inner-core region and its vicinity has a strong implication for Joaquin’s hairpin turn.

著者

新田 勍 水野 孝則 高橋 清利

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.70, no.1, pp.447-466, 1992

被引用文献数

43

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1986/87エルニーニョ発生期に起きた、様々な対流活動と流れの場に関する、時間・空間変動の特徴について調べた。この時期、インド洋から太平洋にかけての熱帯域では、季節内変動(ISV)、超雲集団(SCC)、双子低気圧、西風バーストが発生、発達、消滅を繰り返した。<br>多くの季節内変動は、インド洋で発生し、超雲集団、双子低気圧、西風バーストを伴って、西部熱帯太平洋へと伝わって行く。1986年に発生した季節内変動の中で、エルニーニョの発達に重要な役割を果たしたと思われる、(1)5月の双子低気圧、(2)8月に発達したITCZ、(3)本格的なエルニーニョの発達と関係した11月の超雲集団、の3例について詳しい時間変化と水平-垂直構造を調べた。<br>超雲集団が赤道上をインド洋から西部太平洋に東進する過程で、下層の西風バーストが海洋大陸上、特にスマトラの地形によって大きく影響を受けることが明らかになった。

著者

菊地 勝弘 堀江 成人 播磨屋 敏生 近野 好文

出版者

公益社団法人 日本気象学会

雑誌

気象集誌 (ISSN:00261165)

巻号頁・発行日

vol.66, no.1, pp.125-139, 1988

被引用文献数

11

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一般に北海道における年平均降雨量や年間の大雨日数は、本州方面に比較して少ない。しかし、北海道胆振支庁管内のオロフレ山系南東斜面では、4月から10月までの7ケ月間の平均降雨量は2,000mm近くにも達し、日降雨量90mm以上の大雨の日も年間4~51回発生し、しばしば災害をもたらし、大雨地域として知られている。近野&bull;菊地(1981)による観測から、この地域の大雨は、その最大降雨量の位置から、山岳型、海岸型、平野型、北西斜面型、その他の5つに分類される。これらのことを更に詳細に調らべるために、この地域にAMeDASその他7ケ所の雨量計に更に独自に16ケ所の雨量計のメソスケールネットワークを設け、1980、81年の2年間、6月から10月にかけて集中観測を行った。雨量計の間隔は約5kmであった。<br>山岳型降雨の場合に限ってみると、最大降雨量は、オロフレ峠(海抜930m)と、白老の滝(海抜380m)付近に現われた。海抜高度が付近の山々に比べて、比較的低い白老の滝付近に最大降雨量が現われる原因を、地形を考慮して考察した。その結果、この斜面の南東側の太平洋からの暖湿気の南東風による移流では、比較的弱い降雨が緩斜面や平坦部で観測されるが、急斜面になる山岳部では強い降雨が観測された。このことから、海岸部から山岳部にいたる沢の形状が水平収束による降雨の増幅をうながしていることが推定された。<br>これらのことを確かめるために数値実験を行った。その結果、単なる上昇流だけでは観測値に達しなかった降雨量は、水平収束の効果を加えることによって、観測値とよい一致を示した。また、山岳部の降雨強度、風速、上層の雲からの降水強度の関係が議論された。その結果、上層の雲からの降水強度が強いほど、また風速が強いほど山岳部の降雨強度が強かった。これらの結果を、数値実験と比較した。山岳部の計算による降雨強度は、上層の雲からの降水強度と風速によって増加した。したがって、もし上層の雲からの降水強度と地上での風速が、かなり正確に得られれば、オロフレ山系南東斜面での山岳部の降雨強度を推定できることが示唆された。

著者

三好 勉信 守田 治

出版者

社団法人日本気象学会

雑誌

気象集誌 (ISSN:00261165)

巻号頁・発行日

vol.71, no.4, pp.529-544, 1993-08-25

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水の物理過程が、地球の大気大循環にどの様な影響を与えているかを調べるために、水の物理過程を全て排除した大気大循環モデルを作成した。水の物理過程を排除したモデルで得られた大循環は、水の物理過程を全て含んだモデルで得られる大循環とは大きく異なった。例えば、地表のアルベドをすべての地点で0.1とした場合、水の物理過程を含んだ場合の地表付近の平均温度は289Kであるのに対して、水の物理過程を排除した場合は279Kである。地表付近での極と赤道の温度差は、水の物理過程を含んだ場合は約40Kであるのに対して、水の物理過程を排除した場合は約100Kである。気温の鉛直分布、南北分布についても、2つの実験で大きく異なった。帯状流は、水の物理過程を含んだ場合は緯度30-50゜で最大となるのに対して、水の物理過程を排除した場合は60-70゜で最大となる。直接子午面循環(ハドレー循環)の南北幅は、2つの実験でほほ同じになったが、循環の強さは、水の物理過程を排除した方がはるかに弱くなった。さらに、波の活動度、間接子午面循環(フェレル循環)の南北幅、強さも、2つの実験で大きく異なった。地表面及び大気の熱収支について詳しく調べ、それらを基に水の物理過程を含んだ場合と排除した場合の熱収支の違いについて議論を行った。また、水の放射過程が熱収支に及ほす影響、および水の蒸発、凝結、カ学による水蒸気輸送が熱収支に及ほす影響について議論を行った。

著者

Hironori FUDEYASU Ryuji YOSHIDA

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.2, pp.439-451, 2019 (Released:2019-04-04)

参考文献数

33

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 during the 38 years from 1979 to 2016. Among the 965 TCs, 90 TCs (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 TCs, such that UL-TCs tended to remain at weak intensity.

著者

Wan-Ru HUANG Po-Han HUANG Ya-Hui CHANG Chao-Tzuen CHENG Huang-Hsiung HSU Chia-Ying TU Akio KITOH

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.2, pp.481-499, 2019 (Released:2019-04-03)

参考文献数

58

被引用文献数

9

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By using the Weather Research and Forecasting (denoted as WRF) model driven by two super-high-resolution global models, High Resolution Atmospheric Model (denoted as HiRAM) and Meteorological Research Institute Atmospheric General Circulation Model (denoted as MRI), this study investigates the dynamical downscaling simulation and projection of extreme precipitation activities (including intensity and frequency) in Taiwan during the Mei-Yu seasons (May and June). The analyses focus on two time period simulations: the present-day (1979-2003, historical run) and the future (2075-2099, RCP8.5 scenario). For the present-day simulation, our results show that the bias of HiRAM and MRI in simulating the extreme precipitation activities over Taiwan can be reduced after dynamical downscaling by using the WRF model. For the future projections, both the dynamical downscaling models (i.e., HiRAM-WRF and MRI-WRF) project that extreme precipitation will become more frequent and more intense over western Taiwan but less frequent and less intense over eastern Taiwan. The east-west contrast in the projected changes in extreme precipitation in Taiwan are found to be a local response to the enhancement of southwesterly monsoonal flow over the coastal regions of South China, which leads to an increase in water vapor convergence over the windward side (i.e., western Taiwan) and a decrease in water vapor convergence over the leeward side (i.e., eastern Taiwan). Further examinations of the significance of the projected changes in extreme precipitation that affect the agriculture regions of Taiwan show that the southwestern agriculture regions will be affected by extreme precipitation events more frequently and more intensely than the other subregions. This finding highlights the importance of examining regional differences in the projected changes in extreme precipitation over the complex terrain of East Asia.

著者

Kuan-Ting KUO Chien-Ming 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.97, no.2, pp.501-517, 2019 (Released:2019-04-03)

参考文献数

21

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 (SW) flow along with the sea breezes to penetrate into the basin. The urban heat island (UHI) effect enhances the sea breeze convergence at the south of the basin and produces strong convection there. The 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 (W) to west-northwesterly (WNW), 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 changes on the PHs in the Taipei Basin by applying the pseudo–global warming approach.

著者

大後 美保 鈴木 雄次

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.21, no.2, pp.52-58, 1943 (Released:2009-02-05)

参考文献数

6

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The coefficients of correlation between the yield of hemp and the weather factors (i. e. monthly mean temperature, monthly amount of rainfall, monthly total number of rainy days and monthly total hours of sunsh ne) have been calculated by the method reported in a previous number of this magazine, for each prefecture in Japan, in each month during the cultivating time. The correlation coefficients calculated are shown in tables 1, 2, 3 and 4.The correlation coefficients are generally small; only, in the north-eastern provinces, air temperature is more closely correlated with the yield than any other weather factor, and that positively, while in the southern part the closest correlation is found between the yield and rainfall. The results of this investigation show that the warm, rainy weather in the cultivation time of hemp is favourable for it in Japan proper.

著者

高山 大 新野 宏 渡辺 真二 菅谷 重平 つくば域降雨観測実験グループ

出版者

日本気象学会

雑誌

Journal of the Meteorological Society of Japan. Ser. II (ISSN:00261165)

巻号頁・発行日

vol.75, no.4, pp.885-905, 1997-08-25

参考文献数

47

被引用文献数

1

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1994年9月8日の午後、突風と降雹を伴う強い雷雲が群馬および埼玉県を通過した。埼玉県北西部の美里町立美里中学校では、校舎の窓ガラスが突風で割れ、教師2人と71人の生徒が負傷した。被害調査、地上観測、高層観測、静止衛星、現業レーダーなどのデータを用いて、雷雲とこれに伴う突風の解析を行った結果、この雷雲に伴って少なくとも3つのダウンバーストが発生したことがわかった。主な解析結果は以下の通りである。3時間以上長続きしたこの雷雲は、約8 m/sのスピードで東南東進し、発達期以降はその直下で10度近くの気温低下と発散風を伴っていた。成熟期には雲頂は約15kmに達し、レーダーによる反射強度の分布は進行方向に対してオーバーハング構造を呈していた。被害調査による雷雲下の降雹域の幅は2力所で顕著な拡がりを示した。この拡がりの見られた場所と時刻は、レーダーで観測された反射強度の核の降下の場所・時刻と一致していた。更に、数地点の地上気象観測データの時空間変換から求めた水平風の分布には、降雹域の拡がりにほぼ対応した場所・時間に明瞭な発散風(ダウンバーストAおよびC)が見られた。ダウンバーストAは、児玉環境大気測定局(KD)とそこから約3kmに位置する児玉郡市広域消防本部の中間で生じたことが、両地点の風向風速記録から明瞭に読みとれる。雷雲通過による降温はこの2地点付近で最も大きく、11度以上に達した。ダウンバーストAは最終的には差し渡し40kmの範囲にまで広がった。雷雲はダウンバーストAを生じた後、急速に衰弱した。KDの自記紙にはダウンバーストAとは別の更なる気温降下と風の発散が記録されており、近くでダウンバーストBが発生したことを示している。KDでダウンバーストBを発生させた雷雲の部分は、被害を引き起こした突風が吹いた時刻には約8km離れた美里中上空をちょうど通過していた。美里中付近の気象観測資料はないが、被害調査やこれらの事実から、美里中近くで第4のダウンバーストが発生した可能性が示唆される。これらのダウンバーストはすべて、ガストフロントの6~10km後方で発生した。雷雲周辺のCAPEは、雷雲通過前後の3時間で1800 m^2/s^2から700 m^2/s^2以下に減少した。相当温位の下層の極大値と中層の極小値との差も同様に、26Kから16Kに低下した。

著者

谷本 誠

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.7, no.10, pp.353-356, 1929

著者

FANG Yongjie LI Bo LIU Xiangwen

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.2019-019, (Released:2018-12-07)

被引用文献数

4

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The boreal summer intra-seasonal oscillation (BSISO) is the predominant sub-seasonal variability over the East Asia (EA) and western North Pacific (WNP) region and critical for seasonal forecast of the EA summer monsoon. This study examines the theoretically estimated predictability and practical prediction skill of the EAWNP BSISO in the Beijing Climate Center Climate System Model version 2 (BCC_CSM2.0), which is one of participants in the Sub-seasonal to Seasonal Prediction Project. Results from the uninitialized free run of BCC_CSM2.0 show that the model reasonably simulates the EAWNP BSISO in terms of its variance, propagation and structure. Measured by the bivariate correlation (> 0.5) and root mean square error (< √2) between the predicted and observed real-time BSISO index, the prediction skill and predictability of EAWNP BSISO are about 14 and 24-28 days respectively. The initial/target strong BSISO cases have a relatively higher prediction skill compared to the initial/target weak BSISO cases. For the theoretically estimated BSISO predictability, similar dependence on target amplitude occurs in the model, while no significant dependency on initial amplitude is found. Moreover, diagnosis of the phase dependence reveals that BSISO is less skillful for the prediction starting from active or active-to-break transition phases of WNP rainfall, whereas it is more predictable when prediction is targeting extreme dry/wet phases of WNP rainfall. Finally, systematic errors are found in BCC_CSM2.0 such as the underestimation of BSISO amplitude and the faster phase speed.

著者

INATSU Masaru SUZUKI Hayato KAJINO Mizuo

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.2019-010, (Released:2018-11-28)

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A set of atmospheric dispersion-deposition model integrations was conducted with a hypothetical emission of radioactive materials consisting of 137Cs, 131I, and 134Cs from the Tomari Nuclear Power Plant in Hokkaido, Japan, which is a snow climate site. Each integration was driven by Japan Meteorological Agency’s meso-scale model analysis data with 5-km horizontal resolution. The initial conditions were those on each day from January 2010 to December 2016 and the integration period was at most 4 days. The target was the area within 30 km of the plant. Extending a unit-mass emission concept, the measure of relative risk is the probability of exceeding the threshold of the maximum effective dose rate based only on exposure from groundshine. Considering that the measure increased monotonically with the ratio of the total emission amount to the threshold, we evaluated the probabilistic risk with its median. The results suggested that the risk was higher in the eastern part of the target area due to the prevailing westerly. The frequent snowfall in winter drags radioactive materials down in the target region, even under an active turbulent condition with strong vertical shear. The composite analysis for wind direction averaged over the target area revealed that the risk was high in the leeside, but that mountains effectively blocked the inflow of the radioactive materials. The results were insensitive to a wet deposition parameterisation. The risk was reduced when we replaced the emission altitude with a higher one than the standard setting. The snow shielding effect was negligible on the short-term radioactivity just after the emission but was substantial on the seasonal change in radioactivity.