著者

Meiji Honda Akira Yamazaki Akira Kuwano-Yoshida Yusuke Kimura Katsushi Iwamoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.259-264, 2016 (Released:2016-09-22)

参考文献数

17

被引用文献数

7

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Synoptic conditions causing an extreme snowfall event in the Kanto-Koshin district occurred on 14-15 February 2014 are investigated through a reanalysis data set. Associated with a developing cyclone passing the south coast of Japan, persistent snowfall exceeding more than 24 hours over the Kofu-Basin resulted in 112 cm snowfall at Kofu. Slow progress of the south-coast cyclone also contributed to the long snowfall duration. An anticyclone developed over the northern Japan (∼1032 hPa) also contributed to this extreme snowfall. This anticyclone brought warm and moist air inflow by southeasterlies forming moisture flux convergence over the Kanto-Koshin district on the morning of 14th when snowfall started in the Koshin district in spite that the south-coast cyclone was located to the south of Kyushu. Further, ageostrophic cold northerlies with high pressure extension from the anticyclone by “cold-air damming (CAD)” would suppress warming with the approaching south-coast cyclone and keep snowfall until the morning of 15th. In other four heavy snowfall events at Kofu, snowfall durations were almost 12 hours. Although anticyclone to the north and CAD were identified in each case, the moisture transport from the southeast was not evident and moisture flux convergence was not formed earlier.

著者

Hiroaki Kawase Akira Yamazaki Hajime Iida Kazuma Aoki Wataru Shimada Hidetaka Sasaki Akihiko Murata Masaya Nosaka

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.39-45, 2018 (Released:2018-03-29)

参考文献数

22

被引用文献数

8

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Extremely small snow cover in the winter of 2015/16 and interannual variations of snow cover over the Japanese Northern Alps are simulated by a regional climate model with 2 km grid spacing based on the Japanese 55-year Reanalysis (JRA-55). Our simulation well reproduces the daily variation of snow depth along the Tateyama-Kurobe Alpine Route, located at the Japanese Northern Alps, as compared to snow depths observed by time-lapse cameras in 2014/15. Our simulations indicate that the maximum snow depth in 2015/16 was the lowest of 16 years at high elevations, especially in the spring. In March 2016, weak cold air outbreaks and inactive storm-tracks cause little precipitation around central Japan, resulting in greatly reduced annual accumulated snowfall than usual at high elevations. Warmer April conditions also contribute to accelerated snow melting, resulting in the disappearance of snow at high elevations one-month earlier than usual. Analysis of large-scale circulations related to past large El Niño years shows a warmer April is a typical response in El Niño events, while weak cold air outbreaks and inactive storm-tracks are contributed by the extratropical internal variation rather than lingering El Niño effects in tropics.

著者

Akira Yamazaki Meiji Honda Akira Kuwano-Yoshida

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.11, pp.59-64, 2015 (Released:2015-05-11)

参考文献数

12

被引用文献数

1 15

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The influence of large-scale atmospheric blocking over the northwestern Pacific on heavy snowfall events in the Kanto area and on the Pacific Ocean side of northern Japan (PNJ) within the time scale of ∼10 days was examined through blocking case studies. The past 14 blocking cases over the Pacific, including the blocking during early- to mid-February 2014 that influenced a record-breaking snowfall over the Kanto area, were analyzed using a long-term reanalysis dataset and local meteorological observation station data. Results reveal that blocking over the Pacific causes large precipitation over the Kanto area and the PNJ by shifting cyclone (storm) tracks towards the east coast of Japan from their usual eastward course across the mid-Pacific via the south coast of Japan. Excessive passing of cyclones caused large precipitation in the Kanto area and snowfall in the PNJ. In the blocking cases with heavy snowfall events in the Kanto area, a strong cold-air inflow over Japan also existed in the lower troposphere originating from east Siberia, which initiated synoptic ground cold-air environments in the Kanto area.

著者

Akira Yamazaki Ao Takezawa Kazusa Nishimura Ko Motoki Kyoka Nagasaka Ryohei Nakano Tetsuya Nakazaki Munetaka Hosokawa

出版者

The Japanese Society for Horticultural Science

雑誌

The Horticulture Journal (ISSN:21890102)

巻号頁・発行日

pp.QH-094, (Released:2023-10-17)

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Chili pepper is cultivated in the absence of fruit-promoting treatments or insect pollinators. The fertilization ability of both males and females, as well as natural self-pollination ability under high temperatures, are necessary for autonomous set fruit under high temperatures. The reproductive traits related to autonomous self-pollination ability and fertilization ability of both males and females after pollination under control (CK) and high temperature (HT) treatments were investigated in this study. ‘Takanotsume’ (TK) showed a significantly higher percentage of autonomous fruit set than ‘Peruvian Purple’ (PP) in both CK and HT treatments, suggesting that TK has a strong autonomous fruit set regardless of temperature. On the other hand, the percentage of autonomous fruit set of PP was 0% in the HT treatment, while autonomous fruit set was observed in the CK treatment. Therefore, TK had autonomous fruit set ability even at high temperatures when PP did not have any. TK had more pollen on the stigma than PP, suggesting that TK has a higher ability for autonomous self-pollination. Flower morphology was not considered a factor in the autonomous self-pollination of TK. In contrast, TK tended to release more pollen than PP. One factor that can support autonomous self-pollination is pollen dispersion. A significant difference was observed in the fruit set rate during artificial pollination between the treatments (CK and HT) of the pollen parent and the cultivars (TK and PP) of the seed parent. In fact, female fertility in TK was higher than that in PP, regardless of the temperature condition. Almost no fruit set of PP was observed via autonomous self-pollination in the HT treatment, but fruits were set by artificial pollination using both the pollen and pistil of PP in the HT treatment. This result is consistent with the finding that PP exhibits decreased autonomous self-pollination at high temperatures. The higher autonomous fruit-set ability of TK than PP under high temperatures may be attributed not only to superior female fertility, but also to its autonomous self-pollination ability under high temperatures. Therefore, pollen dispersal ability under high temperatures was considered a key factor for autonomous fruit-set.

著者

Ayumu Kono Ayumu Kawabata Akira Yamazaki Yuma Ohkubo Adriano Sofo Munetaka Hosokawa

出版者

The Japanese Society for Horticultural Science

雑誌

The Horticulture Journal (ISSN:21890102)

巻号頁・発行日

pp.QH-037, (Released:2022-11-30)

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We investigated the effect of ultraviolet-B (UV-B) irradiation on the development of black spot disease caused by Diplocarpon rosae Wolf., which is a major problematic disease in rose (Rosa × hybrida) production. The growth of D. rosae colonies was suppressed on potato dextrose agar (PDA) medium under UV-B irradiation (peak wavelength: 310 nm; full width at half maximum: 30 nm) at an intensity of 15 μW·cm−2 with 1 h daily treatment. In addition, black spot conidia were inoculated to the rose ‘Danjiri Bayashi’ leaves and the effective growth suppression of black spot symptoms was observed on the leaves under UV-B irradiation. Next, various rose cultivars were planted in two greenhouses: one for supplemental UV-B irradiation treatment and one as a control without the treatment. In the UV-B irradiation greenhouse, the roses were irradiated at an intensity of 3–5 μW·cm−2 every day from 23:00–23:30 and 0:00–0:30 (total: 1 h). No chemical pesticides other than a starch agent for aphid control were used throughout the experiment. With the exception of the data for ‘Papa Meilland’ in 2019, UV-B irradiation significantly reduced the number of leaves infected with black spot disease. In September 2019, the non-UV-B irradiated ‘Danjiri Bayashi’ and ‘Papa Meilland’ had severe black spot symptoms on over 20 leaves. The number of plants with black spot symptoms increased in July 2020 compared to 2019. On the other hand, in UV-B irradiated plants, fewer black spot symptoms were observed than in non-UV-B irradiated plants. Although some visible damage was observed in the UV-B irradiated plants, the chlorophyll and carotenoid contents in the leaves decreased, indicating that UV-B irradiation had a certain negative effect on the photosynthetic apparatus. Over a five-month period, the cumulative number of flowers in the UV-B irradiation greenhouse did not decrease, and actually increased, depending on the cultivar, compared to the control treatments. Our results suggest that supplemental UV-B irradiation is effective at suppressing black spot disease in roses and can contribute to the production of pesticide-free edible rose production.

著者

Akira Yamazaki Takeshi Enomoto Takemasa Miyoshi Akira Kuwano-Yoshida Nobumasa Komori

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.41-46, 2017 (Released:2017-03-25)

参考文献数

26

被引用文献数

7

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The observation operators in the local ensemble transform Kalman filter (LETKF) were improved to enable use of observations in the vicinity of the poles in the data assimilation system composed of the atmospheric general circulation model for the Earth Simulator (AFES) and the LETKF. The improved observation operators allow to assimilate the observations located south (north) of southernmost (northernmost) Gaussian grid latitudes. An algorithm for searching the nearest observations from an analyzed grid for error covariance localization was also modified to efficiently assimilate observations near the poles.The new algorithms were incorporated into the LETKF, and the impacts of routine radiosonde observations at the South Pole during the periods of July 2012 and January 2013 were assessed. The radiosonde observations suppressed an artificial expansion of the analysis ensemble spread which occasionally caused numerical instability in the upper troposphere and the lower stratosphere over the Antarctic regions. The analysis was also improved in the Antarctic regions.