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Volume 27, Issue 4
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R. YOKOTA, H. TAKAHASHI1972 Volume 27 Issue 4 Pages 123-128
Published: May 25, 1972
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSIn this paper, we compared the distributions of horizontal wind speed measured in a region of complicated configuration to those of its model area in the wind tunnel.
The results obtained may be summarized as follows:
(1) In the model test with 1/1000 reduced scale of the field, the distributions of the wind speed at 1.0mm height in the model area had a good similarity to that of 1.0m height in the field.
(2) The wind erosion has happened at two areas in this field (Fig. 1). The results of its model test in the wind tunnel showed that the wind erosion in area (D) and area (E) were caused by SW∼W wind and S wind, respectively.
(3) At first we predicted that the wind was converged by the shelter belt (I), consequently the wind erosion was brought about at the area (E) in the field. However, it was cleared that removing the shelter belt increased the wind speed at the area (E) and expanded the area of wind erosion on the model test of wind tunnel.View full abstractDownload PDF (2533K) -
Seishi ISOBE1972 Volume 27 Issue 4 Pages 129-135
Published: May 25, 1972
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSSignals from two uni-directional sonic anemometers at different levels in the canopy of mature corn of 3m high have been analysed with the method of “fast Fourier transforms” to yield energy and cross spectra and cross correlation coefficients. The spectral analysis reveals the formation of characteristic components in a frequency range of 0.11Hz to 0.18Hz. These compoments are shown to travel upward at least above a level of 85cm. The components in a range below the characteristic band of frequency seem to move downward. The cross correlation coefficients with time delay indicate that on the average the fluctuations of wind velocity travel upward and that the travelling speed increases with mean wind speed in the vegetation.
A constant-temperature hot-wire anemometer has provided the data for the energy spectra in a frequency range of 1Hz to 50Hz and their variations with level and wind speed condition in the vegetation. The spectra disclose the excitation of distinctive frequency components under moderate to strong wind conditions. Supplementary measurements of energy spectra of turbulence behind cylinders and plates in a wind tunnel and their comparison with the spectra in the corn provide an interpretation for the distinctive components to be due to stems of the corn. No conspicuous extremals which could be attributed to leaves are found in the spectra.
For details, reference should be made to: Isobe, S. (1972) A spectral anlysis of turbulence in a corn canopy. Bull. Nat. Inst. Agric. Sci. (Japan), Ser. A, No. 19, 101-113.View full abstractDownload PDF (733K) -
Taichi MAKI1972 Volume 27 Issue 4 Pages 137-143
Published: May 25, 1972
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSAt Syowa Station in Antarctica, the author observed the wind velocity profile from March to September in 1970 and the temperature profile from March 1970 to February 1971.
The results are summarized as follows:
(1) The frequency distribution of the stable temperature gradient is about 88 per cent in winter (from May to September) and about 75 per cent throughout the year. The variation pattern of the requency distribution of the temperature is nearly symmetric in autumn (March and April) and spring (October and November), and is distorted in other seasons, namely the peak of the frequency distribution shifts to the small temperature gradient in winter and to the great temperature gradient in summer.
(2) The phenomenon of Kernlose type also appears at the annual variations of TX (tropospheric maximum temperature), T20 (temperature at 20m height) and T1 (temperature at 1m height) which are averaged of the observations with inversion. The temperature differences between Tx, T20, and T1 increases in winter.
(3) The more the thickness of an inversion layer increases, the less the rate of an inversion appearance increases.
(4) The value of the temperature difference decreases in order of Tx-T1, T20-T1 and T10-T1. The maximum value of the temperature difference is found in July and the minimum value of the temperature difference in January and February.
(5) The ratio of (T10-T1)/(T20-T1) is great in autumn and is small in summer. The ratio of (T10-T1)/(T20-T1) in winter and spring is nearly equal to the mean of the summer-value, which shows the maximum in the year, and the autumn-value, which shows the minimum in the year. The observation results, described above make clear that the temperature profile in winter and spring shows a linear variation and that the temperature gradient in the lower atmospheric surface layer remarkably increases in autumn and decreases in summer.
(6) To make clear the relation between the wind velocity and the temperature gradient, the observed data are plotted on the Fig. 9. From the distribution of the plotts, it is possible to estimate the maximum value of the temperature gradient related with the wind velocity. This maximum value is called maximum limit of the relation between the wind velocity and the temepreture gradient. The curve shape of the maximum limit looks like an orthogonal hyperbola. The temeprature gradient remarkably increases in the case of the wind velocity at 10m (U10) below 5m/sec and decreases in the case of the wind velocity above 8m/sec, with which the snow cover begins to drift.View full abstractDownload PDF (964K) -
Masatoshi M. YOSHINO, Mitsuko HOSHINO, Michio OWADA1972 Volume 27 Issue 4 Pages 145-152
Published: May 25, 1972
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe total area of wind breaks reaches 37, 629 ha in Hokkaido in 1969. In order to rearrange the wind breaks, it was hoped to study the distribution and the density of wind breaks in relation to local wind conditions. Here, an example of the studies in the Shari-Abashiri region is reported.
The writers made firstly investigations into the density and the prevailing directions of wind breaks through interpretation of air photos and secondly field observations of wind-shaped trees, such as Larix leptolepis, Fraxinus mandshurica and Populus spp., as an indicator of the local wind conditions. The following results, as given in the figures attached, were obtained: The Shari-Abashiri region studied can be divided into three from the viewpoint of wind conditions. They are; i) the northern foot region of Mt. Shari, ii) the coastal region and the marshy region along the Shari River, and iii) the hilly region between the cities, Koshimizu and Kiyosato.
The characteristics of each regions are: In the first region, the density of wind breaks is 100m/ha on the average with the maximum 150-200m/ha. The southeasterly winds prevail up to 100m above sea level on the foot as called “Sharidake-oroshi (fallwind from the Mt. Shari)”, which blows especially in spring. The direction of the wind breaks are mainly from SW to NE. In the second region, the density of wind breaks is lower than 25m/ha. This coastal region is lower than 20m above sea level and has 2-3km width. There prevail the northerly winds from the Sea of Okhotsk. Where the marshy, low land extends 8-10km inland from the coast, the northerly winds invade into there. In the third region, the density of wind breaks is mainly 50-75m/ha. Almost all wind breaks run in W-E direction. The prevailing wind directions are southerly, but northerly in an exceptional year with cool summer, like in 1971.View full abstractDownload PDF (3548K) -
(1) Influence of shelter-hedge on vertical profile of air temperatureR. YOKOTA, H. TAKAHASHI, M. HAGIWARA1972 Volume 27 Issue 4 Pages 153-158
Published: May 25, 1972
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSIn order to make clear the influence of shelter-hedge upon thermal conditions of cultivated fields, measurements of wind and temperature profiles were made in the lee of model windbreaks. Experiments were made in a wind tunnel as shown in Fig. 1 and on a plowed field. The geometrical sizes of model shelter-hedges and the hydraulic charactriestics of underlying surfaces are shown in Table 1. The results obtained are summarized as follows:
1. The similitude between phenomena observed in the wind tunnel and field experiments was examined by the following relations proposed by Inoue (1959) and Nemoto (1961, 1967) for wind profile in the surface air layer
HN/HM=ZON/ZOM, UN/UM=(HN/HM)1/3
Relationships among wind speed, roughness and height of shelter-hedge used in the experiments satisfied approximately the relations mentioned above, indicating that the results obtained in wind tunnel experiments may be applicable to field conditions.
2. Fig. 4 indicates clearly that the vertical distribution of air temperature in the lee of the shelter-hedge (closeness 100%) is not very affected by thermal stratification in air flow. However, the distribution pattern of air temperature in the lee of the shelter-hedge (closeness 100%) changed considerbly by wind speed as shown in Fig. 5. Especially, the temparature profiles observed in field experiments (N) was much affected by wind speed.
3. The temperature rising effect of shelter-hedge was studied in relation to the closeness of sheter-hedge in the wind tunnel. The model shlter-hedges with the closeness of 100, 60, 50, 40 and 30% were set in the wind tunnel and temperature profles in the lee of these shelter-hedges were measuried by using thermocouples. Two-dimensional distributions of air temperature as shown in Fig. 7 indicate that the temperature rising effect is highest in the lee of shelter-hedge with closeness of 60%.View full abstractDownload PDF (731K) -
Nobuyoshi SASAKI, Takeharu BOKURA1972 Volume 27 Issue 4 Pages 159-163
Published: May 25, 1972
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSSimultaneous observations at 4 points were made in July, 1970 in the plain of the Oirase river, Aomori prefecture in order to investigate the characteristics of Yamase wind.
The observational stations were established, one at the seaside and the other three on some rice fields of inland at distances of 4, 12 and 28km from the coast respectively. Observations were made for micrometeorological elements in general up to the height of 1m above the ground.
The effects on Yamase wind passing from coast over inland were generally slowing down of the velocity, the humidity and water drops in the atmosphere were decreased, and the temperature rose.
The air temperature at a linear distance of 10km from coast was about 2°C higher than that of the coast. The rate of increase in air temperature was affected by solar radiation energy.
When Yamase wind is broken up by obstructions like houses and trees, the wind velocities and water content in the atmosphere are significantly affected.
At the base of the mountains the thickness of layer of clouds increased. Furthermore the solar radiation energy decreased and the air temperature was lower during heavy Yamase wind.
It was considered that these phenomena were influenced by the location of the mountain.View full abstractDownload PDF (3037K)
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