農業気象

冬季の幼木茶園における温度分布と樹体の凍結

高市益行, 米谷力

1990 年 46 巻 2 号 p. 71-77
発行日: 1990/09/10
公開日: 2010/02/25

DOIhttps://doi.org/10.2480/agrmet.46.71

ジャーナルフリー

抄録を表示する抄録を非表示にする

Relationship between temperature distribution and freezing of a young tea plant (Camellia sinensis L., cultivar ‘Yabukita’, two years old) was investigated in a field condition. Freezing of the plant was detected by temperature rize with fine thermocouples (0.1mm in diameter) inserted in the stems and attached to the leaves.
The lowest nighttime temperature of the plant (plant hight: 65cm) was observed on leaves at about 35cm above ground. The leaf temperature was 3-4°C lower than the air temperature at 1.5m hight (Ta₁₅₀) when wind speed U₁₅₀ and net radiation Rn were below 0.5m/s and -60W/m², respectively. Freezing of plant body was found to spread to all shoots through trunk in a relatively short period of from several to a dozen minutes. A boundary of frozen and unfrozen part was at the lowest part of trunk in a straw mulch layer.
Relatively wet conditions when dew-point temperatures around leaves at about 35cm height were above -2°C, freezings did not occur until leaf temperatures fell below about -2°C in spite of adequate dew formation. Conditions when dew-points were -2 to -4°C, freezing temperatures of the leaves were changed with and nearly equall to the dew-points. More dry conditions when dew-points were below -4°C, freezings occurred at almost constant temperatures of -4°C, and they seemed not to be related to the dew-points. In these conditions, freezings might occur first in stem tissues without dew formation on leaves.

抄録全体を表示

PDF形式でダウンロード (420K)
抄録

1990 年 46 巻 2 号 p. 78
発行日: 1990/09/10
公開日: 2010/02/25

DOIhttps://doi.org/10.2480/agrmet.46.78

ジャーナルフリー

PDF形式でダウンロード (77K)
香川県高瀬盆地周辺における冬季の晴天日の局地気象特性の観測

真木太一, 黒瀬義孝

1990 年 46 巻 2 号 p. 79-86
発行日: 1990/09/10
公開日: 2010/02/25

DOIhttps://doi.org/10.2480/agrmet.46.79

ジャーナルフリー

抄録を表示する抄録を非表示にする

The local meteorological observation was carried out at Takase Basin and the south west slope of Osa Mountain, Kagawa Prefecture on clear-fine day in winter, Jan. 19-21, 1988.
The cold air lake was observed at the bottom of Takase Basin and the thermal belt observed at the slopes of 100-500m of Osa Mountain and 100-200m of Asahi Mountain. The vertical differences of both air and surface temperatures for the typical inversion layer were 6-7°C and about 10°C, respectively, and the thickness of the inversion layer was 80-100m at the basin bottom. In the case of small cold air current, the cooling seemed to be larger, because the air current was easy to stand on the gentle slope. The pan-type distribution of isotherm was recognized at the basin.
The change of wind direction and the frequency of weak wind of 1m/s were higher at the basin bottom. The cold air current of 1 to 3m/s was observed at the slope and its wind speed was relatively heigher at the lower region of the slope. The cold air current seemed to blow from the elevation of about 400m. The stronger the wind speed of the air current was, the higher the air temperature was at the foot of the mountain, however, the air temperature seemed to be constant in the case of wind speed over 3m/s.
The relative humidity and the appearance frequencies of dew and frost were higher at the basin bottom, but lower at the slope and the foot of the mountain in the case of cold air current. The air was dry and its temperature was high at the observation base of 160m in the blowing period of cold air current. The amounts of dew and frost were few, and the latent heat flux by evapotranspiration was occasionally released from the soil surface even at night. As the cold air current blowing from the thermal belt is the warmer wind at the slope and supplies the sensible heat to the crop at the foot of the mountain, its utility is high as meteorological resources along with the thermal belt.

抄録全体を表示

PDF形式でダウンロード (540K)
数種の植被内における変動光

鈴木晴雄, 田中伸一

1990 年 46 巻 2 号 p. 87-92
発行日: 1990/09/10
公開日: 2010/02/25

DOIhttps://doi.org/10.2480/agrmet.46.87

ジャーナルフリー

抄録を表示する抄録を非表示にする

変動光については連続照射の人工光を間欠照射の変動光へと制御し, それを栽培へ応用した例もあるが, 実際の植被による変動光の実態はほとんど明らかにされていないのが現状である。本実験では, 室内実験にて各植被による変動光の特徴を得ることを目的とした。
(1) 変動光に関する風洞実験から, 各植被 (約20cm高) の変動光のスペクトル密度が一定のレベル以上になる周波数は, 風速1.7ms^-1の場合, イネ (28Hz)>トウモロコシ(22Hz)>ゴボウ(17Hz)>ニンジン(13Hz)・ソラマメ(11Hz)・ダイズ(10Hz)の順序であった。6種の植被についてピーク周波数は弱風(1.7ms^-1)と強風(2.5ms^-1)の場合ともに大差はなく, いずれも1.5～3.5Hzであった。ピーク値は風速の増大につれ比例して大きくなり, この関係は周波数の範囲についてもみられた(Fig. 4)。
(2) 生育にともなう変動光の変化については, ソラマメではスペクトル波形の周波数の範囲と風速との関係が草高と一定の関係になかった。トウモロコシではその関係は明瞭となり, 草高が高くなるほど周波数は低くなる傾向にあった。

抄録全体を表示

PDF形式でダウンロード (338K)
移動プローブによる地表面付近の気象要素のプロフィルの測定

文字信貴, 鱧谷憲, 小元敬男

1990 年 46 巻 2 号 p. 93-96
発行日: 1990/09/10
公開日: 2010/02/25

DOIhttps://doi.org/10.2480/agrmet.46.93

ジャーナルフリー

PDF形式でダウンロード (182K)
東北タイのユーカリ植林と林間栽培について

高垣美智子

1990 年 46 巻 2 号 p. 97-101
発行日: 1990/09/10
公開日: 2010/02/25

DOIhttps://doi.org/10.2480/agrmet.46.97

ジャーナルフリー

PDF形式でダウンロード (409K)
黒龍江省中日農業気象研究会成立大会参加報告

宮田明

1990 年 46 巻 2 号 p. 103-106
発行日: 1990/09/10
公開日: 2010/02/25

DOIhttps://doi.org/10.2480/agrmet.46.103

ジャーナルフリー

PDF形式でダウンロード (556K)

J-STAGEへの登録はこちら（無料）