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Volume 50, Issue 3-4
Displaying 1-13 of 13 articles from this issue
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Emissivities in the Window Region for Plant Canopies and its Effects of Plant Cover Ratio and OthersXiufeng WANG, Ikuo HORIGUCHI, Takashi MACHIMURA1994 Volume 50 Issue 3-4 Pages 177-183
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSInfrared thermometers have been adopted for measurements of surface temperature, and are used routinely to measure the temperature of the earth's surface from satellites. To obtain accurate measurements of surface temperature by infrared thermometry, it is necessary to know the surface emissivity in the atmospheric window region. In this study, emissivities of plant leaves and canopies were measured by the box method using an infrared thermometer.
Results are summarized as follows:
(1) Soil emissivity increases with an increase in soil water.
(2) The emissivity of potato leaves was lowest among the six varieties of plants measured, and that of gramineous leaves was the highest.
(3) Inclination angles of leaves less than 60° do not affect leaf emissivity.
(4) Higher emissivities of leaves lead to higher values for plant canopy emissivities.
(5) The water content of soil has an effect on the emissivities of plant canopies.
(6) When vegetation cover is heavy, the emissivities of plant canopies are close to, or greater than, those of leaves.
Above and the reported results confirmed that plant leaf temperature is measured with considerable accuracy, if a value of 0.97 or 0.98 is used for the emissivity setting of the infrared thermometer. A value of -0.04-+0.01 must be added to plant leaf emissivity for measurements of canopy temperature.View full abstractDownload PDF (899K) -
Taichi MAKI, Mingyuan DU, Borong PAN, Kenji UEMURA1994 Volume 50 Issue 3-4 Pages 185-195
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe authors studied climatic characteristics at Turfan Desert Research Station in northwest China on the basis of the meteorological measurements for the periods from July, 1990 through December, 1992. The desert climate data were compared with those in a nearby oasis. Main results were as follows:
(1) Maximum air temperature was 47.9°C on August 3, 1990 and June 29, 1992, and maximum surface soil temperature 84.7°C on July 16, 1992. Monthly mean wind speed was lowest at 1.3m/s in January and highest at 3.5m/s in July, and annual mean wind speed was 2.2m/s. Annual precipitation from July 1, 1991 to June 30, 1992 was 16.0mm and 2-year mean precipitation from 1991 to 1992 was 8.8mm.
(2) Wind speeds of strong wind season from April to August were lowest at early morning and highest from evening to midnight. Annual prevailing wind direction was from NE to NNE, however, most frequent wind direction for the strong wind season was from W to WNW. Foehn and strong wind over 20m/s occurred on about 30% and 10%, respectively, of the days in July and August.
(3) The instantaneous maximum wind speed correlated well with the daily maximum 10-minute mean wind speed for either the strong wind season and the whole year. The proportional coefficient of the former to the latter speed was 1.41 as a gust factor.
(4) Evaporation rate from soil surface at the dry land of Turfan was very low below 1mm per day, while that from small pan-type evaporimeter was very high at about 25mm per day on fine days in summer. Amount of evapotranspiration calculated by gradient method was generally smaller than that by heat budget method, however, the increaing rate of the former was larger than that of the latter under the condition of strong wind. By comparison, the evapotranspiration rate calculated by the heat budget method was erroneously high in the dry land.
(5) Air and soil temperatures inside an oasis were lower than those in a desert at daytime in summer and higher at night in winter, and annual and diurnal fluctuations of the temperatures were smaller inside than outside the oasis. After rainfall, the air and soil temperatures increased slowly inside the oasis than outside, because of the higher soil moisture content and relative humidity.View full abstractDownload PDF (1482K) -
Wei GU, Seiji HAYAKAWA1994 Volume 50 Issue 3-4 Pages 197-206
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSA 102-year temperature record in Sapporo, Hokkaido, Japan was studied with regard to the relationship between occurrence of low temperature in summer and cooling damage in rice.
As an index of low temperature in summer, the ratio of the deviation from normal temperature to the standard deviation was calculated for four terms in summer, i.e. May to September, May to June, July to August, and the month of September. On the basis of the four ratios, the temperature record in Sapporo from 1889 to 1990 was classified with the maximum likelihood partition method into four levels, of which level 0 designates no low temperature, and levels 1 to 3 designate the degree of low temperature in ascending order. Of the 102 years, 50 years were classified as level 1 or higher.
The 50 years of low temperature in summer were further examined with regard to the relationship between occurrence of low temperature and cooling damage in rice. Fuzzy cluster analysis indicated that, in the years of cooling damage, there were four types of cool summer year considering both the degree of cool summer damage and low temperature occurrence, i.e. low temperature in early summer, low temperature in mid-summer, low temperature in early and late summer, and low temperature in whole summer.
Finally, the occurrence of low temperature in summer was related to the variation of rice yield in Hokkaido. The yield loss caused by cooling damage was related to the low temperature level as defined in this study.View full abstractDownload PDF (1322K) -
Shumin LI, Kenji KURATA, Tadashi TAKAKURA1994 Volume 50 Issue 3-4 Pages 207-211
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSSome experimental results of solar radiation transmissivity into a Chinese-style lean-to greenhouse were described. The greenhouse is east-west oriented and its north wall, north roof and east- and west-gable walls were made of opaque materials.
A scale-model greenhouse with the floor area of 20cm (width)×160cm (length) was constructed and 16 solar cells (each detecting area is 11mm×17.5mm) were set on the floor at its central part. Experimental observations were conducted from December 1992 to June 1993 in Tokyo (35°41′N) at an interval of about 45 days on fine days as well as on overcast days. The results on fine days showed that in winter and spring daily transmissivity distributions on the floor were quite uniform except for some low radiation points due to shades of the purlines. In summer time, on the other hand, daily transmissivity at the north part of the greenhouse showed remarkably lower values compared to those of the rest part. Transmissivities during 9:00-15:00 were higher than those during the early or late hours of the day in every season. The results on an overcast day showed that diffuse radiation transmissivity on the floor was quite nonuniform because of the shade effect of the north wall and north roof to the diffuse radiation.View full abstractDownload PDF (690K) -
GuiRui YU, Keiichi NAKAYAMA, YanLei YI1994 Volume 50 Issue 3-4 Pages 213-220
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSSoil can be regarded as a source and a storage of water in soil-plant-atmosphere continum (SPAC). To make clear the characteristics of moisture retention of the soil in relation to other soil properties is part of the basic work of water dynamic analysis in SPAC. In this study, water retention characteristic curves and other soil properties were measured for 50 samples representing 5 different kinds of soil from the northeastern region of China.
From the results, a new empirical equation for moisture characteristic curve was proposed. The parameters of the equation had physical meaning and could be estimated by the percentage of micro-aggregate and the organic matter content in the soil, and the geometric mean of soil particle size. Furthermore, an equation to describe the rate of soil water absorption was also proposed. Parameters in the equation depended upon the specific surface area of the soil, the organic matter content in the soil and the percentage of soil particles less than 0.01mm.View full abstractDownload PDF (1029K) -
Nobuo KUME, Kunio TAKEZAWA1994 Volume 50 Issue 3-4 Pages 221-224
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe time of bud opening in the first crop of tea plants was estimated using the one-dimensional nonparametric DVR (developmental rate) method and two-dimensional nonparametric DVR method.
The experiment was carried out from 1991 through 1993 at the Saitama Tea Experiment Station, and times of bud opening were observed. Meteorological factors taken into consideration were maximum temperature, minimum temperature, mean temperature, precipitation, and duration of sunshine for every day of the experiment.
Nonparametric DVR functions were derived from nine sets of data; DVI (developmental index) was set at 0.0 on the spring skiffing day. The standard deviation of prediction error of the best DVR function obtained from two meteorological factors (minimum temperature and precipitation) was about 0.8 days, while the standard deviation of the observed durations from the spring skiffing day to the time of bud opening was about 9.1 days. This result guarantees that the nonparametric DVR method predicts the time of bud opening in the first crop of tea plants accurately enough for practical purposes.View full abstractDownload PDF (467K) -
Shinji YOKOYAMA, Kiyotune SHIRAI, Satoru TAKAHASHI1994 Volume 50 Issue 3-4 Pages 225-229
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSBoth the equation of estimating evaporation (E) from soil surface and that of estimating temperature (T0) at soil surface are obtained from the heat balance equation applied by the theory of heat transfer. It is difficult to observe the value of E, but it is comparatively easy to observe the value of T0. If the estimated results of T0 coincide well with the observed results, it is certified that not only the heat balance equation but the method to estimate E is accurate. Therefore, we examined a method to estimate T0 from the meteorological factors such as air temperature, relative humidity, solar radiation, wind velosity which can be measured without difficulty. The results are as follows:
1) The effective rediation (when T0 is equal to the air temperature) QR0 is calculated from the solar radiation and albedo.
2) The relative humidity and the soil moisture content at soil surface can be estimated from albedo.
3) T0 is more influenced by QR0 than the Soil heat flux QB.
By the results obtained above, we estimated T0. Those calculated values were almost equal to measured values. Consequently, we confirmed that the method to estimate E is appropriate.View full abstractDownload PDF (641K) -
Koji UCHINO, Akihiro KONO, Kazuyoshi SAKODA1994 Volume 50 Issue 3-4 Pages 231-234
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
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Tohoku Chapter1994 Volume 50 Issue 3-4 Pages 235-248
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
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Eiji GOTO1994 Volume 50 Issue 3-4 Pages 249-250
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
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1994 Volume 50 Issue 3-4 Pages 251-256
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (859K) -
[in Japanese]1994 Volume 50 Issue 3-4 Pages 257
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (133K) -
[in Japanese]1994 Volume 50 Issue 3-4 Pages 258
Published: December 10, 1994
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (124K)
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