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Volume 57, Issue 2
Displaying 1-5 of 5 articles from this issue
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Hiroaki KOMODA, Tetsuo KOBAYASHI, Jun'ichi TESHIMA, Yutaka UENO2001 Volume 57 Issue 2 Pages 69-77
Published: June 10, 2001
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe wind and temperature structure over a grass-covered slope of Mt. Kuju were examined by making meteorological observations for two months at the Kuju Agricultural Research Center of Kyushu University, located on the south-southeast-facing slope. The following characteristics were revealed from the observations.
1) The rate of increase of surface wind speed with increasing altitude on the slope was smaller when the wind blew down-slope or up-slope than cross-slope.
2) The friction velocities of down-slope or up-slope winds under rather high wind conditions were on the average larger than those of cross-slope winds at the same wind speed.
3) For WSW winds, when the wind speed exceeded a critical value the surface wind speed over the upper part of the slope, which is immediately downwind of a ridge that projects southward and ends suddenly halfway down the hill, increased less than over the lower part as a result of the formation of a wake.
4) On clear nights, the downward sensible heat flux in the 1.5-2.8m air layer over the slope was almost the same, or about twice as large as the net radiation, which suggests that the cold-air-drainage layer (CADL) produced by radiation cooling near the surface was often warmed by entraining ambient air.View full abstractDownload PDF (3880K) -
Hisashi KATO, Yukio AKAI2001 Volume 57 Issue 2 Pages 79-92
Published: June 10, 2001
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSA simple numerical model, which is based on an atmospheric diffusion model considering the vertical subsidence of sea salt particles and the semitheoretical estimation of their generation and vertical distribution, is proposed to estimate the amount of wind-driven sea salt or sea salt damage at any point along the coastal area under strong onshore wind conditions. The performance of the model was evaluated through sensitivity studies of the calculation methods for the deposition, adsorption and on the vertical distribution pattern of sea salt particles over the ocean used as initial data. The results were compared to data observed under typhoon conditions in Okinawa Prefecture. The estimated initial vertical distribution pattern of sea salt particles for each size class reproduced well the observed pattern under the strong onshore wind conditions. The atmospheric concentration, deposition and adsorption of sea salt particles observed under strong onshore wind conditions over a platform-like topography near the coast can be reproduced by the model when the interception of sea salt particles by the cliff and the observation efficiencies are considered. In the model, the deposition and adsorption of sea salt particles over the coastal area are proportional to the wind speed to the third or fourth power, and they are most sensitive to the wind speed near the coast. These features are reasonably consistent with the results of studies reported in the literature. Through a series of evaluations, it was suggested that this model is useful for the simple evaluation of sea salt damage over a coastal area under a flat or simple topography.View full abstractDownload PDF (6034K) -
Ken HAMOTANI, Nobutaka MONJI, Koji YAMAGUCHI2001 Volume 57 Issue 2 Pages 93-99
Published: June 10, 2001
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSA REA (Relaxed eddy accumulation) system for long-term CO2 flux measurement was developed. Long term continuous measurements were achieved by applying a repeating intake and exhaust sampling bag system, by adapting a durable electric valve which can withstand frequent switching, and by real time computation of the REA-coefficient using the temperature signal.
Density correction (WPL correction) is shown to be necessary in the REA method as well as in the open path eddy correlation method. A simple correction method using a heat budget was proposed.
Continuous CO2 flux measurement was made over a cypress forest from October, 1997 to August, 1998, when the system was stuck by a lightning. Typical 10-day averages of CO2 flux were about -0.05mg m-2 s-1 in January and -0.27mg m-2s-1 in August.View full abstractDownload PDF (784K) -
Tsuyoshi HONJO, Hiroshi SHONO2001 Volume 57 Issue 2 Pages 101-106
Published: June 10, 2001
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSIn this study, leaf tip (declination) angles were measured by image processing method and by using a 3-D digitizer. The 3-D digitizer senses magnetic wave from the source and determines the 3-D location of the sensor. While the 3-D digitizer measures the precise position of the leaf, it is time comsuming, especially if there are many leaves. For this reason, we also tested a method to determine general information on leaf tip angles by image processing, we call this the “texture analysis method”. In this procedure, only photos were necessary for the calculation of general characteristics of leaf tip angles.
The 3-D digitizer (Isotrak, POLHEMUS Inc.) was used for the measurement of leaf position of F. benjamiana L. a plant that has about 300 leaves. Within about 60cm from the source, the digitizer showed good precision.
The results of the texture analysis method were compared with measurements of the 3-D digitizer. Generally they showed good agreement and indicated that the texture analysis method was effective for the estimation of leaf tip angles.View full abstractDownload PDF (3471K) -
Tetsuo KOBAYASHI, Hiroshi TANI, Yoshitaka KUROSE, Osamu TSUKAMOTO, Tai ...2001 Volume 57 Issue 2 Pages 107-115
Published: June 10, 2001
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (1249K)
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