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斜面下降風に関する農業気象的研究II斜面下降風に関する農業気象的研究IIAN0005519X
Agro-meteorological studies on the down slope wind Ⅱ |
"/今岡, 円七/"今岡, 円七 ,
"/Imaoka, Enhichi/"Imaoka, Enhichi
22
(
4
)
, pp.375
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409 , 1966-12 , 九州大學農學部 , Faculty of Agriculture, Kyushu University
ISSN:0368-6264
NII書誌ID(NCID):AN0005519X
内容記述
In the part I of this paper I have described the method of observation on the slope wind in the night carried out chiefly at a small island (Hakatajima Island in the Inland Sea of Seto) and partly at a large slope of a mountain (Ogi-yama, Beppu City, Oita Pref.), and the obtained results from the micro-meteorological point of view. Now in this part II, I shall explain mainly my observation on temperature distribution associated with the slope wind and the frost damage on crops from the point of view of agro-meteorology. Obtained results are summarized as follows: (1) At each bottom of the northern and southern slopes a low temperature zone due to the cooling layer was observed to exist. But the depths of the cold airs were different, i.e., less than 10 meters and more than 50 meters respectively, probably due to the fact that the northern slope was connected to the sea, and the southern slope to a small basin where a cold air lake was formed. (2) On each slope, a high temperature zone was observed, height ranges being 30-80 meters on the northern slope and 60-110 meters on the southern slope respectively. (3) Observed number of frosty days on the southern slope amounted to more than 30 in a year at the foot of the slope, and decreasing gradually upward till it began to increase again near the top of the hill. A frostless zone was observed at the height of 90-100 meters above the sea level, quite in agreement with the high temperature zone. (4) It is known in the Inland Sea of Seto that the occurrence of frost damage of Pelargonium species coincides very well with the distribution of frost-fall, and they should be cultivated in areas where frosty days never exceed 16-20. But it was made clear from our observations that when the average temperature fell to 3℃ and the average wind velocity reached 5.3 meters per second in the coldest month owing to the outbreak of an unusually cold wave, etc., wintering was impossible in almost all the area. (5) It is usual in the area of the Inland Sea of Seto that the low temperature damage on the mandarin orange is comparatively small and ignored from the economical point of view. But under a certain condition of the unusually low temperature such as January to March in 1963, the low temperature damage was remarkable. The states of damage distribution in the Inland seemed to be coincided with our results of the observation on cooling layer and air temperature.
晴夜において斜面上で冷却した空気は低地に流下し,そのために谷間等ではいちじるしく低温となる.地理的条件等によつて異なるが,高度差70mぐらいの谷間と尾根上で,気温差が4℃以上に達することはまれでない.このような局地的気温差は,前篇で説明した冷却層の影響によつて生ずると考えてよく,降霜分布の傾向もそれらとよく一致している.本篇では農業気象的な立場からこれらの問題を究明することとする.瀬戸内海の伯方島(Lat.34°14’N,Long.133°05’E)にある小さな丘状地で,1960年から1962年かけて,晴夜における冷却層の性状と,それによつて生ずる接地気温又は降霜状況等の局地性に関する観測を行なつた.これらの結果を要約すると次の如くなる. (1) 小丘状地(120m M.S.L.)の北斜面下方は海に接し,南斜面下方は小盆地となつており,両斜面の下方にそれぞれ冷却層による低温域が見られるが,海に接する北斜面の冷却層の厚さは10m以下であるのに対して,南斜面下方の盆地では冷気湖を形成し,冷却層の厚さは50mに達している. (2) 南斜面では海抜110m,北斜面では80m以上の高度から気温の逓減が初まつている.従つて南斜面の60-110m,北斜面の30-80mの地域はそれぞれ高温地帯となつている. (3) 両斜面とも上方の高温帯と低地の低温部との接地気温差は4.5-5.0℃ に及び,又南斜面下方では年間降霜日数が30日を越すが,丘頂近くの海抜90-100mの間は無霜地帯となつている.瀬戸内海地域におけるゼラニウムの凍霜害発生状況は降霜分布の状態と非常によく一致しており,降霜日数16-20日以下の地域で栽培することが越冬の第1条件であるが,異常寒波等により最低月の月平均気温が3℃,月平均風速が5.3m/Sに達すると,ほとんどすべての地域において越冬が不可能であつた.瀬戸内海地域における例年の柑橘の低温障害の程度は,経済的水準において無視してよいと思われる.然し1963年1・2・3月の異常低温の条件下では低温障害が目立ち,島内における被害の分布状況は夜間冷却層,接地気温分布の観測結果と関連が見られるが,季節風の風圧による機械的作用も,低温障害発生に関係していると思われる.
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https://qir.kyushu-u.ac.jp/dspace/bitstream/2324/22980/1/p375.pdf
