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Volume 54, Issue 3
Displaying 1-7 of 7 articles from this issue
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Alan Edwin GREEN, Yousay HAYASHI1998 Volume 54 Issue 3 Pages 225-234
Published: September 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSSurface measurements of sensible heat flux (H) over rice paddies were made for several days using a Larger Aperture Scintillometer (LAS) operating in the near-infrared. At such wavelengths temperature (T) normally dominates refractive fluctuations and humidity (Q) fluctuations are considered insignificant. However, under conditions of low Bowen ratio β, as encountered over rice paddies the combined effects of temperature and humidity fluctuations are theoretically shown to contribute to the refractions and may be a consideration when calculating H from scintillation data. Bacause of low β and overcast skies daytime fluctuations in the refractive index structure parameter (10-16m-2/3<Cn2<10-14m-2/3) were smaller on average than nocturnal values but greater than the LAS signal-to-noise figure (10-17m-2/3rms). Corrected half hourly scintillometer data for enhanced Q fluctuations did not improve the Hsc comparison to the eddy correlation Hec which tended to underestimate for unstable but overestimate for stable conditions over a small dynamic range of data (-100<H<100Wm-2).View full abstractDownload PDF (3271K) -
Sei-ichiro YONEMURA, Masaharu YAJIMA, Hidemitsu SAKAI, Masahiro MOROKU ...1998 Volume 54 Issue 3 Pages 235-245
Published: September 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSRice yield was estimated at all the third mesh points in Japan for the condition of elevated CO2 concentration and increased temperature with a growth model. Growth parameters of the model for 36 principal Japanese japonica type varieties were employed for the calculation. In cases of the temperature change in -2, +2 and 4°C, decrease of the total yield of Japan was estimated to be about -14, -5 and -12%, respectively. Under the conditions with temperature increment of 2°C, only rice yield in Hokkaido rose. In central and southern part of Japan, rice yield decreased as the temperature rose, however, the reduction could be avoided by advancing the planting date.
Effect of CO2 concentration on rice yield was incorporated into the radiation use efficiency which was calculated from light-photosynthetic curves of canopies in growth chambers. Rice yields increased from 10 to 15% depending on the radiation intensity when CO2 concentration was elecated from 350ppm to 1200ppm. Under the lower the radiation intensity, the increase of rice yield caused by elevated CO2 concentration was higher.View full abstractDownload PDF (6156K) -
Atsushi MARUYAMA, Kazuhiko OHBA, Yoshitaka KUROSE1998 Volume 54 Issue 3 Pages 247-254
Published: September 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSA simple model to estimate the daily mean water temperature of paddy fields from observed meteorological data was developed. The model is based on a crop growth model coupled to an equilibrium water temperature model. Using this model, the water temperature of a paddy field can be estimated from only three factors namely, air temperature, solar radiation, and water vapor pressure, observed a nearby weather station. Validity of the model was examined on actual paddy fields of different style of cultivation, under warm temperate climate. There was a good agreement between observed and calculated temperature. This suggests that the water temperature of paddy fields can be estimated well using this model without any correction to adjust for the style of cultivation.
The model was applied to estimate the water temperature of paddy fields under normal and abnormal weather conditions. Under normal weather conditions, there were regional differences in water temperature of paddy fields caused by the differences in elevation and cultivation period of paddy fields. Under abnormal weather conditions, the deviation from normal of water temperature was directly proportional to the deviation from normal of air temperature. A 1.0°C decrease in air temperature during a cool summer year corresponded to a 1.0°C decrease in water temperature of paddy fields, whereas a 1.0°C increase in air temperature during a hot summer year corresponded to a 0.6°C increase in water temperature of paddy fields.View full abstractDownload PDF (2816K) -
Taichi MAKI1998 Volume 54 Issue 3 Pages 255-266
Published: September 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSAn investigation was carried out at the Jagaramogara basin in Tendo, Yamagata from 1996 to 1997. Obtained results are as follows:
(1) There are wind caves or holes with changeable wind direction, blowing out cool air from the holes in summer half year of May to October and drawing in cold air in winter half year of November to April at the basin bottoms of Ohjigoku and Shimojigoku in Jagaramogara. The author found that the entrances of wind in summer and exits of wind in winter are the stone holes from the region below the cliff of Amayobari west slope to the region fallen down on upper Murakumonoike, and also found that the same regions mentioned above are the entrance in summer and the exit in winter including with the upper holes of the sloped area at Shimojigoku basin.
(2) The hole air temperature was observed 0°C at the end of May, 2 to 3°C with relative humidity of 100% and wind speed of 1.5m/s from July to August, maximum of 5.3°C in the middle ten days of October and minimum of -5.4°C in the last ten days of January. There are ices in the wind cave at least until June. The air temperature of blowing wind from the hole in summer is low based on the conduction heat contacted from the ice to air and by cooling of sublimation, fusion and evaporation heats.
(3) Inversion of air temperature frequently appeared at night from autumn to spring and is fairly even at the daytime in summer. Strong cooling continued for a long period by adding to the cold air lake with temperature inversion and to cold air blowing out from the holes of basin bottom under a proper condition.
(4) The cold air current being relatively dry and warm is observed and typical wind speed is fairly strong of 2.0 to 2.5m/s. The air current starts to blow from the elevation 760m on Amayobari Mt., slides down on the slope and joins in the basin. The cold air lake is developed by radiation cooling. The thermal belt appeared at the elevation of 560 to 570m.
(5) The plant profile indicates the reverse distribution to elevation which the semi-alpine plants of dwarfing with cold-drought resistance are found near the lower part of basin. There are many plant species, but the number of holes were decreased recently.View full abstractDownload PDF (3771K) -
Takeharu BOKURA1998 Volume 54 Issue 3 Pages 267-274
Published: September 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (1112K) -
Guo Yu QIU, Kazuro MOMII, Tomohisa YANO, Sadanori SASE1998 Volume 54 Issue 3 Pages 275-282
Published: September 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSENWATBAL (ENergy and WATer BALance) is a numerical model to calculate soil evaporation (E) and plant transpiration (T). In this study, ENWATBAL model is tested in a sandy bare soil field and a sorghum field. Results reveal that the measured and estimated E agree with each other well. In the bare soil field, regression coefficient between the measured and estimated E is r2=0.92. In the sorghum field, regression coefficient between the measured and estimated E is r2=0.63. Estimated and measured T are consistent with each other and the regression coefficient between them is r2=0.63. It is also shown that the calculated and measured evapotranspiration (ET) agree with each other and the regression coefficient between them is r2=0.70. Therefore, it is concluded that ENWATBAL model can evaluate E, T, and ET accurately under the coarse sandy soil and lower evaporation conditions.View full abstractDownload PDF (939K) -
Satoru TAKAYA, Masayuki NOTO1998 Volume 54 Issue 3 Pages 283-287
Published: September 15, 1998
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (544K)
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