著者

斎藤 隆幸

出版者

日本農業気象学会

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.23, no.2, pp.65-74, 1967-09-30 (Released:2010-02-25)

参考文献数

9

被引用文献数

1 4

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In order to study the nocturnal cooling of plant communities, the fall of temperature of a wheat field during night was calculated for various values of net radiation and of wind speed above the surface of the wheat field, 60cm height and with 4.4 of L A I. The results of the calulation were compared with the fall of temperature of the bare soil surface during night.As it is observed that the thermal condition of the plant layer is approximately in equilibrium for the time just before sunrise, the vertical distribution of leaf temperatue, air temperature and water vapour density within the plant layer at the time of sunrise are calculated with various values of net radiation and of wind speed at the height 40cm above the surface of the wheat field on the assumption of equilibrium condition.The calculated profiles of leaf temperature and air temperature for 0.10cal·cm-2·min-1 of net radiation are shown in Fig. 4 for the values of 0.5m·sec-1 and 3.0m·sec-1 of wind speed. It is seen from Fig. 4 that difference between the temperatues of the upper part of plant layer and of soil surface under the plant layer is about 9.0°C for 0.5m·sec-1 of wind speed and about 0.5°C for 3.0m·sec-1.The fall of temperature during night was obtained from the difference between the calculated value of temperature and the temperature at the time of sunset. The temperature at the time of sunset was assumed to be equal to that at the top of the inversion layers. The fall of leaf temperature of the upper part of the wheat field, shown in Fig. 3, is in very close agreement with observational values. As seen in Fig. 3, the temperature fall increases rapidly with decreasing the wind speed below 1m/sec.The fall of temperature of the bare soil surface was also calculated for the radiation values and the wind speed at the height 50cm above the soil surface. The calculated results of the fall are in good agreement with those of BERLYAND (1956). The variation in the fall of temperature of the bare soil surface with wind speed is not so apparent as in the case of the wheat field.By use of both calculated results of the wheat field and of the bare soil surface, comparison was made of the fall of temperature of the upper part of the wheat field and of the bare soil surface under the same meteorological conditions. From the results it can be inferred that the night minimum temperature of the upper part of the wheat field is lower than that of the bare soil surface for the condition of calm wind, but that for windy condition the reverse is the case.

著者

林 陽生

出版者

日本農業気象学会

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.48, no.1, pp.57-64, 1992-06-10 (Released:2010-02-25)

参考文献数

15

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To investigate dependencies in the magnitudes of a waving ear on mean wind speed, field observations were carried out over a barley filed in the ripe stage. Fluctuating displacements derived from HONAMI were measured using a newly designed 2-dimension strain sensor. The velocity fields were measured by a sonic anemometer-thermometer.A coherently waving phenomena of HONAMI appeared and was evaluated by the fluctuating displacements of a single ear of the stand. Dividing a time series of the fluctuating displacement into five typical bands of frequency by use of an analog filter, it was shown that there are two dominants of 0.5-Hz and below 0.1-Hz in the original. The bands were from a natural frequency and a gustness of wind respectively. Comparing the amplitudes, the natural frequency contributed remakably to the original fluctuation of HONAMI.Magnitudes of an instantaneous ear-displacement, which represents 0.5-0.6-Hz of frequency, varied with increments of the mean wind speed within a range of 2.6-4.4-m/s. Except for this range, the dependency between the amplitude and the wind speed was not clear.Instantaneous changes in lateral displacements and velocity fluctuations were quite similar except for the component of higher frequencies. Under such circumstances, an ear-displacement will appear to infulence strongly the aero-dynamical properties of the canopy boundary layer.The force per unit length acts on a waving ear generates by a relative velocity of u-dx/dt. Here, u is the mean wind speed, and dx is the displacement of an ear from its mean position during dt. Using this concept, drug force was evaluated under two criteria for leeward ear-moving and ear-standing. Under the windy conditions, the force loaded on an waving ear reduced by 10% against the standing criterion with dx=0. On the other hand, the reduction rate became small down to 4% of the standing criterion under the condition of weak wind.

著者

Toshichika Iizumi Gen Sakurai Masayuki Yokozawa

出版者

日本農業気象学会

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

pp.D-13-00023, (Released:2014-04-03)

参考文献数

42

被引用文献数

3 10

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The consequences of observed changes in climate and management on yield trends in major crop-producing regions have implications for future food availability and access. We presents an assessment of the impacts of historical changes in sowing date and climate to the maize yield trend in the United States (U.S.) Corn Belt from 1980 to 2006, using large-area crop modeling and data assimilation technique (the model optimization based on the Markov Chain Monte Carlo method). The model calibrated at a regional scale successfully captured the major characteristics of the reported changes in yield and the timing and length of maize growth periods over the Corn Belt. The simulation results using the calibrated model indicate that while the climate change observed for that period likely contributed to decrease the yield trend, the positive contribution from the reported earlier shift of sowing date offset the negative impacts. With given spread in the assessment results across previous studies and this study, the credence of the conclusion that the negative impacts of the climate change on the U.S. maize yield trend are more likely attributed to the decreasing growing-season precipitation trend than to the temperature trend increased. This study addressed an emerging use of large-area crop modeling and data assimilation to attribute observed change in crop yield trend to climate and management.

著者

佐々木 喜一 木村 玲二 伊志嶺 正人 大田 守也

出版者

日本農業気象学会

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.61, no.1, pp.77-81, 2005 (Released:2006-07-21)

参考文献数

7

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Evapotranspiration from a sugar cane field was observed during the summer season in the Miyako Islands. Interpolation was also conducted for the data deficit period by using the bulk transfer coefficient and evapotranspiration efficiency, which were represented as a function of solar radiation and soil water content. Evapotranspiration was 6.4 mm day-1 in late June, and decreased gradually. It was under 3.5 mm day-1 (100 W m-2) at the end of October.

著者

真木 太一

出版者

日本農業気象学会

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.39, no.3, pp.225-234, 1983-12-10 (Released:2010-02-25)

参考文献数

3

著者

中山 敬一 浦野 永久 今 久 松岡 延浩

出版者

日本農業気象学会

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.48, no.4, pp.359-363, 1993-03-10 (Released:2010-02-25)

参考文献数

5

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To clarify the effects of water blooms on the heat balance in a water body, some heat balance components were observed in a small water pond (length and breadth of 160cm; depth of 45cm) made of polystyrene board of 15cm thick.Floatage of stratified water blooms increased the albedo on the water surface but decreased the net radiation in daytime. The water temperature near the surface was increased in daytime, and decreased in nighttime as a result of the floatage of water blooms. The amount of heat storage in the water body was reduced by the stratified water blooms, because of suppressing effect for transmission of solar radiation into the water body. The amount of latent heat flux was increased in daytime by the stratified water blooms but decreased in nighttime depending on the lower water surface temperature and the reduced heat storage in the water body.

著者

日下部 正雄

出版者

日本農業気象学会

雑誌

農業気象 (ISSN:00218588)

巻号頁・発行日

vol.16, no.1, pp.34-37, 1960-06-30 (Released:2010-02-25)

参考文献数

3

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著者は主として西日本災異誌によつて梅雨によつて起つたと推定される災害について調査した。まず梅雨による災害が全災害のうちでどのような位置を占めるかをみると, 古代においては干ばつが首位を占め梅雨についての記録が比較的少なかつたが, 14世紀ごろから次第に重要性を増し, 17世紀ごろになると梅雨は台風についで注目すべき位置を占めるようになつている。またこのころになると単なる長雨による災害ではなく, 梅雨末期の大雨が大きな役割を演ずることを, 洪水の旬別ひん度や, 川潮の旬別ひん度などから明らかにした。また山潮が風化花崗岩土地帯に多いことを示した。