著者

青野 靖之 小元 敬男

出版者

The Society of Agricultural Meteorology of Japan

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.49, no.4, pp.263-272, 1994-03-10 (Released:2010-02-25)

参考文献数

29

被引用文献数

11 18

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The change of the monthly mean temperature for March since the 11th century is estimated from the records of cherry blossom in old documents. The dates given as cherry blossom festivals in old diaries and chronicles are assumed as full flowering dates of Prunus jamasakura, one of the native cherry tree species of Japan. The temperatures are estimated by means of DTS method, which has been used to estimate flowering date from temperature data. It is shown that computations for the recent 40 years proved that the decadal average values of the March temperature may be obtained by the method for P. jamasakura with the accuracy of 0.1°C of the root mean square error.It is shown that the entire study period can be roughly divided into three subsections. In the first period (the 11-13th centuries), the March appeared to be generally very warm compared with other periods, however, accuracy of the estimated values are rather poor because decadal averages are computed from relatively small number of years due to missing of records.For the second period (the 14-16th centuries), there was a period of warming of 2°C from 1470's to 1610's, otherwise the decadal averages suggest large fluctuations, at least partly attributed to poor quality of full flowering data of P. jamasakura.For the third period (the 17-20th centuries), temperatures generally tend to be estimated in low values, especially estimations in 1690-1710's and 1810-30's continued to the present is noticeable. The rise amounts to 3.4°C seems due both to urban warming and larger scale warming over the central Japan roughly the same degree.

著者

小元 敬男

出版者

The Society of Agricultural Meteorology of Japan

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.24, no.1, pp.33-38, 1968-06-20 (Released:2010-02-25)

参考文献数

11

被引用文献数

2 2

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This paper gives climatological information on hail occurrence in Kanto-Koshin District. Hailstorms occur mostly in the warm season in this area, therefore, climatology of warm season hailstorms is studied in detail.Data of the recent eitght years are used to obtain a frequency distribution, for it is possible to determine hail patterns for most of hailstorms occurred during this period. As shown in Fig. 4, there are three distinct maxima and two secondary maxima in the frequency distribution. It is noteworthy that all of these maxima are situated about 70km east through southeast of major mountain areas.Locations of hailswaths observed during the eight year-period are examined. The result (Fig. 5a-5d) indicates that the local farmer's tradition “hailstorms always take the similar routes” is not entirely untrue. A number of interseting features may be pointed out from the result, some of them are as follows:1) Most hailstorms in this region move east through southeastward. However, in the western region most hailstorms are eastward moving, whereas eastern region there are more southeastward moving storms.2) Hailstorms moving east-southeastward are associated with thunderstorms developed near the NW-Gunma Mtns or the Nikko Mtns, whereas those moving northeastward are associated with thunderstorms developed near the Chichibu Mtns.3) Hailstorms move from mountain areas toward lower lands, they rarely cross big mountain regions, and sometimes change courses to follow valleys.Finally, long term variations of hail occurrence are studied. Although long term increase of hail days seems to exist (Fig. 6), at least partly, it is attributed to the tendency that fewer records remain for earlier days. However, the records for recent 20 years indicate increase in hailstorm activities druing the last several years. Computations of correlation coefficients between different areas and stations are made. The result suggested that for long term view point, hail occurrence is quite random.

著者

青野 靖之 小元 敬男

出版者

日本農業気象学会

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.45, no.4, pp.243-249, 1990-03-10 (Released:2010-02-25)

参考文献数

25

被引用文献数

19 22

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Blooming dates of Prunus yedoensis at 38 sites are estimated by using “the number of days transformed to standard temperature (hereafter referred as DTS)” for the 25 year period starting 1961. The sites are all located at or in the vicinity of the meteorological observatories of Japan Meteorological Agency. The standard temperature for DTS in this study is chosen 25°C, for the temperature characteristic Ea, a value [71.1kJ mol-1] is used for all stations. Both of these values are the same as those in our previous paper, although CGS unit was used before.It is shown that by this first estimation RMS errors of estimated blooming dates fell within a range 1-3 days except for stations in regions of southern coasts of Kyushu Is. and Izu Is. An attempt of reducing errors, in the first place, readjustment of accumulated DTS was made. This enable us to reduce RMS error up to 0.5 days from the previous computations. But this approach was not very effective at southern stations. Large RMS error in these warm regions seemed to be due to incomplete transition of rest break or large interannual variation of this process. An adjustment of estimation of blooming date at southern sites is made by applying the concept of chill-unit which is the weighted hour corresponding to the effectiveness of chilling to rest completion. It is shown that this procedure reduced RMS error of blooming dates to 2.32 days from 6.64 days at Hachijo Is., and at all stations in warm regions the error reduced to about 2 days.

著者

小元 敬男 青野 靖之

出版者

The Society of Agricultural Meteorology of Japan

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.45, no.1, pp.25-31, 1989-06-10 (Released:2010-02-25)

参考文献数

21

被引用文献数

22 15

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An attempt is made to estimate blooming dates of Prunus yedoensis for 21 meteorological stations in Japan by using DTS (the number of days transformed to standard temperature). The starting date for computation at each station is determined by correlation analysis. At many stations the date lies between 40 and 55th day from January 1st.The number of days transformed to a standard temperature (in this study 25°C is used) at each station is computed by adding characteristic temperature of each day from a starting date to blooming date for various temperature characteristic (Ea). The estimated blooming date is the date when accumulated value of DTS reached at that of mean observed blooming date for the site.It is found that 17kcal mol-1 for Ea gives minimum error when averaged over all sites. Using this Ea and D2 which is the starting date determined from error analysis, computations are made to estimate blooming dates at each station between 1961 and 1985. It is shown that at stations in Hokkaido and Tohoku districts, RMS errors between the observed and the calculated blooming dates fall between 1 and 2 days. At stations in other areas, the errors range between 2 and 3, except for Hachijo where it becomes 6.7 days. The large error at this southernmost station seemed to be attributed to year to year change of degrees of rest completion of Prunus yedoensis, which affect effectiveness of temperature just before blooming.

著者

小沢 行雄 小元 敬男 八木 鶴平 米谷 恒春

出版者

独立行政法人防災科学技術研究所

雑誌

防災科学技術研究資料

巻号頁・発行日

vol.34, pp.1-20, 1978-12-20

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The National Research Center for Disaster Prevention carried out a five-year hail suppression research project ending in 1972. A rocket system was developed for cloud seeding. In the system, the rocket was to be launched from a mobile launcher reaching 6000--7000m above the ground, and completely burned away in the air during its falling time after seeding. The number of effective nuclei produced by the AgI composite loaded was more than 10^<12> (per gram of AgI) at -10℃. Results of field experiments using the rockets were presented at the Seminar of Cumulonimbus Modification of Tropical Nature (Miami, USA, 15--19 Feb. 1971) and International Conference on Weather Modification (Tashkent, USSR, 1--7 Oct. 1973). Manuscripts for these are reprinted here at the end of this report, with the abstract of a paper on effectiveness measurement for the AgI composite.

著者

本間 幸治 青野 靖之 小元 敬男

出版者

The Society of Agricultural Meteorology of Japan

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.51, no.4, pp.321-327, 1995-12-10 (Released:2010-02-25)

参考文献数

17

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The relationship between temperature and the southern limits of temperate deciduous trees in Japan is discussed by using two indexes of temperature. One is the mean temperature of the warmest month to represent summer condition, and another is the chilling hours (accumulated hours below 7.2°C (45°F)) for winter. Eight species of deciduous trees (Zelkova serrata, Fagus crenata, Aesculus turbinata, Pterocarya rhoifolia, Betula ermanii, Quercus mongolica, Ulmus davidiana and Acer mono) were chosen for this purpose. It appeared that the chilling hours are effective in determining the southern limit of Zelkova serrata, suggesting at least thermal condition in winter is important in the warm side distribution for this species. For other species, the case in which winter condition may affect southern limits is found in the coastal areas and the relatively low latitude region of Japanese mainland.The impact of global warming on the potential probability of occurence for Fagus crenata in Osaka Prefecture and its vicinity is also examined. For a 1.5°C mean temperature rise, the potential probability becomes 0.02-0.21 from the present 0.13-0.68 in Mt. Izumi-Katsuragi and Mt. Koya area, and 0.24-0.70 from 0.65-0.76 in Mt. Kongo. For a 3.0°C rise, the probability decreases to 0.04-0.34 in Mt. Kongo. In the other two areas, it will become almost 0 suggesting the climatic condition becomes too warm for the occurence of this species.

著者

小元 敬男 鱧谷 憲 嚴 香姫

出版者

THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES

雑誌

水文・水資源学会誌 (ISSN:09151389)

巻号頁・発行日

vol.7, no.2, pp.106-113, 1994

被引用文献数

7

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日本の都市の気象台のデータは1950年代と1960年代に急速な乾燥化を示したが,1970年頃に変化傾向が急変し,年間の変動を除いて以後ほぼ一定になっている.東京や大阪のデータは相対湿度の増加傾向すら示唆している.一方,非都市域の気象官署では最近明瞭な乾燥化が観測されている.このため相対湿度及び水蒸気圧の都市内外差は近年,減少傾向になっている.急速な乾燥化の起こっていた時期には,水蒸気量の減少と昇温が同時的に相対湿度を低下させていた.最近の湿度の都市内外差の減少は非都市域の乾燥化という相対的なものだけではなく,様々な人間活動による都市大気への水蒸気の放出量の増加の効果も寄与している.今日の東京及び大阪における都心部と郊外の相対湿度の差はほぼ温度差に起因している.わが国の大都市における乾燥化は夏の蒸し暑さを僅かではあるが和らげる効果をもたらしている.

著者

小元 敬男 文字 信貴 平田 尚美 梶川 正弘 竹内 利雄 吉野 正敏

出版者

大阪府立大学

雑誌

自然災害特別研究

巻号頁・発行日

1985

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本年度は、降ひょうと突風の実態の把握及び基礎研究に必要なデータを得る目的で、分担者のほゞ全員が群馬県で観測を行った。6月前半には、レーダー観測、突風観測、ひょう粒の分析の実験を実施、7月15日〜8月15日の期間には上記の他に高層気象観測、気圧分布観測、短期間ではあるがドプラーソーダによる観測を行った。更ル、5月15日〜8月15日の期間、記録計による100地点での降ひょう観測を行うなど、北関東夏季の積乱雲対象としてかつてない充実した研究観測を実施したのであるが、昨夏は群馬県における雷雨は異常に少なく予期したほどのデータは得られなかった。しかし、この観測期間中に観測本部のある群馬県農業総合試験場にひょうが降り、また地元の協力者から分析用の大きなひょう粒が提供されるなど、ひょうの基礎研究に役立つ資料が得られた。更に同地域における下層大気の昇温が積乱雲発達に及ぼす影響の研究に必要なデータも得られた。例年より少なかったが、上記期間中に発生したひょう害及び突風(災)害の現地調査も行った。その他の分担研究課題の成果として、ひょう害の変遷に関する研究では、関東甲信地域のひょう害は1950年頃までは5月下旬を中心とするピークが一つあっただけであるが、その後7月下旬を中心とするピークが現れ顕著になりつつあることなど幾つかの新らたな気候学的事実が明らかにされた。また、防ひょうネットの研究では、千葉県の実験地に激しい降ひょうがあり、実際の場合について、種々の網目のネットの被害防止効果を測定できた。無被害地の実験データと併せて、防ひょうネットの最適網目は10mmであることが確められた。激しい雷雨の常習地域で長期にわたって連続観測を行ったにも拘ず、異常年に当ってしまい、充分データを得ることができなかった。この種の研究は根気よく続ける必要がある。