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Volume 54, Issue 1
Displaying 1-11 of 11 articles from this issue
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Xiaochuan ZHANG, Yasuyuki AONO, Nobutaka MONJI1998 Volume 54 Issue 1 Pages 1-11
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThis paper proposes a method to estimate the urban surface heat fluxes using Landsat TM data in conjunction with routine data from meteorological observatory and direct field measurement data. The sensible and latent heat fluxes are evaluated independently using bulk transfer formulae. The ground cover classification, surface albedo, surface temperature and the normalized difference vegetation index (NDVI) are deduced from two Landsat TM images on Aug. 6, 1990 and Dec. 6, 1988. A field measurement is carried out to obtain the relationship between the moisture availability and relative humidity for no-vegetation ground using band-pass covariance technique to measure the turbulent sensible and latent heat fluxes over concrete surface.
The distribution of each pixel and mean value for each kind of ground cover show that the net radiation in urban area has a relatively conservative behavior with little spatial variability. Conversely, the sensible and latent heat fluxes have clear spatial variability. The high sensible heat flux corresponds to high building (urban center) and residential area, while the relatively low sensible heat flux corresponds to forest area in parks and open water. The latent heat flux is very low in high building and wooden residential area (mean values less than 37Wm-2 in summer and 1Wm-2 in winter). But in residential area with some vegetation and forest area, latent heat flux increases to 77 and 194Wm-2, and the mean Bowen ratio decreases to 4.6 and 1.6 in summer, respectively. Since the amount and activity of vegetation is higher in summer, there is a greater spatial variability of heat fluxes in summer than in winter.View full abstractDownload PDF (6271K) -
Yoshitaka KUROSE, Kazuo FUKAISHI, Yousay HAYASHI, Kazuhiko OHBA1998 Volume 54 Issue 1 Pages 13-21
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe Ohzu Basin is located in the north western part of Shikoku Island as is shown in Fig. 1. As in other basins in Japan, basin fog appears frequently from autumn to winter. In order to make clear the climatological characteristics of basin fog at the Ohzu Basin, Ehime prefecture, and understand its role as an element of agro-climatological resources, observations were carried out from Sep. 8, 1995 to Feb. 5, 1996. The sites were located at bottom of the basin and on mountainside faced to the center of the basin. The latter site was situated above the upper surface of the fog layer which appears typically in the Ohzu Basin. Spatial distribution of the fog were also analyzed using the LANDSAT images provided on Dec. 5, 1985 and Dec. 13, 1988.
The results obtained in this study were summarized as follows:
(1) The total number of fog day reached 46 days during the present observation period mentioned above. In the most frequent period, fog occurred at the ratio of one day to two day in October and November.
(2) Dispersion time of the fog changed seasonally accordance with a shift of time of sunrise, and the fog has lasted 4 hours or more after the sunrise under dominant foggy conditions.
(3) The meteorological characteristics of foggy day were shown as follow, attenuated of solar radiation in the morning, decreased of radiative cooling in nighttime, and low temperature until fog dissipate.
(4) Several % of monthly total solar radiation was shaded by fog layer at the basin bottom site. Total time of saturation condition indicated by R.H.=100% on foggy days became 21 hours at the site of mountain slope. At the basin bottom site, it reached 493 hours during the period of the observation.
(5) Upper surface of the fog layer was limited to a height about 300m above the sea level, and distributed horizontally along lower part of the Hiji River. The maximum height was affected by the surrounding topography.
(6) In the Ohzu Basin, hamlets on the mountain slope distributed zonally above the fog layer. This indicates that the fog has a remarkable influence on human life of mountainous region. On the other hand, the chinese cabbage-producing district was formed in the foggy area. Utilizing this foggy climate of the basin, high quality chinese cabbage with soft leave are produced in the basin bottom.View full abstractDownload PDF (1473K) -
Jun SUZUKI1998 Volume 54 Issue 1 Pages 23-29
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSFilm mulch is being used in many farm lands because it improves the environment for cultivation by suppressing water evaporation from soil surface, maintaining a mild soil moisture condition, and maintaining the soil temperature higher than the bare soil surface, in addition to protecting against pests and diseases. Crop cultivation in cool high lands (such as the Shinshu Plateau) can be made possible with the introduction of film mulch. However, as the direct infiltration in the root zone are lower in fields where film mulch is used than in bare soil fields, and this raises fears that droughts would be exacerbated.
Experimental comparisons of the soil moisture condition and flow between mulched bed and furrow space using the soil moisture measurement technique at many positions and many depths were carried out in the fall of 1995 in field planted with Chinese cabbage (Brassica pekinensis Rupr.), and in the spring of 1996 in field planted with cabbage (Brassica oleracea L.). The results are summarized as follows;
(1) The shallow topsoil of the mulched beds had less soil moisture than furrow space and bare soil even after light rains at low soil moisture condition. The sowed areas (hold of the mulch film) in mulched beds, however, were moisture than the surrouding of sowed area. But one or two days after rainfall, soil moisture condition in mulched bed and furrow space were almost same.
(2) As the crops grew, the soil moisture became lower than furrow space due to the water uptake by the crops' root system. In the soil layer below the root zone, i.e. at a depth of more than 0.3m, soil moisture is moved from the furrow space to the mulched bed by the gradient of soil moisture potential caused by the soil moisture uptake by the root system.
These results propose that occasional plowing in the furrow space causes an increase in the infiltration rate of rain water, and facilitates the movement of moisture from the furrow space to root zone of the mulched beds.View full abstractDownload PDF (867K) -
Junsei KONDO1998 Volume 54 Issue 1 Pages 31-41
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSUsing the micrometeorological data (Harazono et al., 1995) obtained at the Arctic Tundra at Barrow, Alaska in the summer of 1993, preliminary analysis was made and the daily and seasonal variations of evapotranspiration, radiation, ground heat flux, and surface temperature were estimated.
On fine days, the value of sensible and latent heat fluxes increased to maximums of approximately 200 to 300Wm-2 during the midday, then decreased to about zero (sensible heat flux) and -30 to -80Wm-2 (latent heat flux) around the time of the sun's northing. It is found that the surface evaporation efficiency β, having a mean value of 0.3, decreases with increasing wind speed. Using a model calculation, it is obtained that the mean value of evapotranspiration at the IBP site for 71 days, from 16 July to 25 August, is 0.89mmd-1 which is 40% of the potential evaporation (defined by Kondo and Xu, 1997a).View full abstractDownload PDF (1428K) -
Tsuyoshi HONJO1998 Volume 54 Issue 1 Pages 43-46
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSA neural network was used to estimate climatic data from topographical factors in areas where observed climatic data do not exist. The neural network with a back propagation algorithm was used as a method of nonlinear multiple regression which has advantages over conventional linear regression, especially when the relation between climatic data and topographical factors is nonlinear.
As an example, four meteorological data (normal value of daily mean temperature, daily maximum temperature, daily minimum temperature and daily mean wind velocity) were estimated for 74 observation points around Shizuoka Prefecture from input data of 13 geological factors such as altitude, latitude, longitude, slope angles etc. The network consists of 3 layers which have 13 units in the input layer, 4 units in the output layer and 26 units in an intermediate layer. A linear multiple regression analysis was also used to compare the characteristics of the methods.
In all cases, the neural network showed smaller errors than the multiple regression. In the case of wind velocity where the data was rather scattered, the neural network showed its advantage clearly. Although the use of the neural network is accompanied by theoretical ambiguity, the result shows precise estimation is possible by neural network.View full abstractDownload PDF (530K) -
Tsutomu WATANABE, Yoshikazu OHTANI1998 Volume 54 Issue 1 Pages 47-54
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSAs a part of an estimation method of the heat storage rate within forest biomass, two simple schemes are presented for a calculation of the heat conduction into a cylindrical material. One is a modified version of the so-called Force-Restore method, and the other is a method based on the digital filter. Both methods are tested against analytical solutions of the heat-conduction equation for given diurnal cycles of the cylinder-surface temperature. The modified Force-Restore method gives acceptable results when the diurnal change in the surface temperature is not very different from a sinusoidal wave of 1-day cycle. The digital filter method can produce correct results for any patterns of diurnal cycles, if the time series of the surface temperature is given for more than 1-day period centered by the evaluation time of heat storage. Both method can be applied to an entire forest, if stems of the forest are classified into adequate classes in terms of their radii.View full abstractDownload PDF (912K) -
Kimio INOUE, Hiroshi ABE1998 Volume 54 Issue 1 Pages 55-61
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSTo study meteorological characteristics of cool foggy easterly (Yamase), by which rice production in the Tohoku region was frequently damaged, we measured temperature of the fog layer resulted from Yamase, using infrared thermal indicator and meteorological satellite (HIMAWARI). These temperature data were compared with wet-bulb and dry-bulb temperatures obtained by a ventilated psychrometer.
Generally, the temperature of fog droplets estimated from infrared thermal indicator was higher than the wet-bulb temperature by about 0∼1°C. This result indicates clearly that fog droplets were cooled by evaporation on the droplet surface.
Under the conditions that the fog layer is homogeneous in liquid water content and fog droplet size distribution, the height of the fog layer can be estimated by the observation of visibility and relative solar radiation flux.View full abstractDownload PDF (3053K) -
Kazushige YAMADA, Tomoyoshi HIROTA, Ryuichi SHIROOKA1998 Volume 54 Issue 1 Pages 63-69
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSReturn periods of continuous snow cover duration at the 24 observation points in Hokkaido were investigated using the Weibull distribution method. The mean value of continuous snow cover duration was in the region of 120 days to 170 days. The differences between the mean value and the value of return periods of continuous snow cover duration at 3, 5, 10 and 30 year intervals were about 7, 14, 21 and 30 days, respectively. The differences between the mean value and the first date of the return periods of continuous snow cover duration at 3, 5, 10 and 30 year intervals were about 6, 10, 15 and 23 days. In the same, the last date of continuous snow cover duration at 3, 5, 10 and 30 year intervals were about 4, 8, 10 and 14 days, respectively. The variation of the return periods of last date was small compared with the first date.View full abstractDownload PDF (865K) -
Junsei KONDO1998 Volume 54 Issue 1 Pages 71-75
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (638K) -
Development of Measurements of Meteorological Environment at the Cultivater LandWorking Group of Meteorological Improvement Studie1998 Volume 54 Issue 1 Pages 76-78
Published: March 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (376K) -
1998 Volume 54 Issue 1 Pages 120
Published: 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (807K)
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