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Volume 33, Issue 2
Displaying 1-8 of 8 articles from this issue
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Tetsuo KOBAYASHI1977 Volume 33 Issue 2 Pages 61-66
Published: September 15, 1977
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe northwestern part of 1890 hectares of Lake Nakaumi is projected to be reclaimed by drainage in the near future. The Honjo area is a paddy land situated on the shore and surrounded by hills 200-500 meters high. These topographical features enhance the development of a local climate. In order to investigate the air temperature characteristics of the Honjo area and the likely changes in local climate caused by the reclamation, eight observation stations with standard shelters were deployed in and near the area. Observations of air temperatures were undertaken during a four-year period 1973-1976.
The results obtained are summarized as follows:
(1) Lake Nakaumi has an appreciable effect on the air temperatures of this shore area throughout the year. The magnitude of the effect changes seasonally and depends on the weather. The influence on the daily minimum temperatures is conspicuous in spring and autumn, especially under calm condition with radiation cooling. The daily maximum temperatures are remarkably influenced by the lake from late winter to spring, when the lake water temperatures are relatively low, under the light to gentle on-shore wind.
(2) Lake Nakaumi acts on the daily minimum temperatures of the shore area as a heat reservoir, the process of which is rather complicated. Some conditions to develop the local circulation system, such as air mass characteristics, seem to play an essential role in the process. In the case of the daily maximum temperatures the process is simple and straightforward. The lake water temperature, the wind speed and direction are the essential factors.View full abstractDownload PDF (691K) -
Y. MIHARA, K. TSURUTA, O. NEMOTO1977 Volume 33 Issue 2 Pages 67-74
Published: September 15, 1977
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSA large orchard of satsuma mandarin located nearest the sea coast of the southern end of Kyushu was completely destroyed by the early frost on the two successive nights in November, 1968. The orchard of 72 hectare area in an artificially flattened dune, 5m above sea level, is divided into 60 rectangular sections; each section, 100m wide and 120m long, is surrounded by a pine-tree hedge 6-8m high and is partitioned further into nine small parts by 1.8m high plastic-net windbreaks set up in two lines and two rows. Under such a perfect protection against wind hazard, about 200 thousand young mandarin trees were planted in the autumn of 1967 and the spring of 1968.
In September of 1968 a typhoon, passing off the sea coast to the north, swept the orchard; however, wind hazard was very slight, only faint discoloration was recognized on leaves during a few weeks after the typhoon.
Unusual severe frost occurred on 15th and 16th of November after a warm spell of about ten days. Nearly 85 percent of mandarin trees in the orchard were injured; most of their trunks were frozen to death. Thus the orchard was destroyed and abandoned one year after establishment. Awful damage due to the early frost, however, was restricted within the orchard with windbreaks on the dune. Significant hazard was hardly recognized in many other orchards on the hillsides adjacent to the destroyed one.
To make clear the reason for severe frost damage in the orchard with cautious windbreaks, observations were done for several nights both in the ruined orchard and on another flat ground with model windbreaks. We come to the conclusions that the night land-breeze, generally called cold air flow, lessens in reality the night chilling of the air near the ground surface, and that much obstruction to the breeze by windbreaks such as in the above mentioned case will cause fabulous coldness on the leeward side of the windbreaks on nights when radiation cooling is prevailing.View full abstractDownload PDF (4795K) -
Tetsuya HASEBA1977 Volume 33 Issue 2 Pages 75-79
Published: September 15, 1977
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSEvaporation rates from isothermal wet surfaces of circular and square plates were measured in laminar air-flow parallel to the surface, in order to clarify the dimension dependence of water-vapor transfer coefficients on the flat leaf of small dimensions for forced-convection.
Below a critical Reynolds number of about 2×104, the average forced-convection transfer coefficient is proportional to the 0.5 power of wind speed.
The average transfer coefficients for circular and square models of larger dimensions with a diameter/side-length above 5 to 7cm agree with the predicted values from the “approximate boundary layer theory”. For smaller models with dimensions below 5 to 7cm, however, the observed coefficients are larger than the predicted. The ratio of the observed coefficient to the predicted one (α) becomes larger as the model dimension (l, cm) decreases. A relation between them leads to α≅1.2l-0.09.
Some experiments on evaporation from the square wet surfaces whose leading edges made part of that of a larger rectangular plate showed that a relative increase in the transfer coefficient could be partly caused by the turbulent transport of vapor around the model edges.View full abstractDownload PDF (481K) -
Satoshi Iwakiri1977 Volume 33 Issue 2 Pages 81-85
Published: September 15, 1977
Released on J-STAGE: February 25, 2010
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1977 Volume 33 Issue 2 Pages 87-97
Published: September 15, 1977
Released on J-STAGE: February 25, 2010
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1977 Volume 33 Issue 2 Pages 98
Published: September 15, 1977
Released on J-STAGE: February 25, 2010
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Taichi MAKI1977 Volume 33 Issue 2 Pages 99-101
Published: September 15, 1977
Released on J-STAGE: February 25, 2010
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1977 Volume 33 Issue 2 Pages 102
Published: 1977
Released on J-STAGE: February 25, 2010
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