松岡 延浩

周辺(越谷,東京,我孫子,船橋)のアメダスデータを使い,松戸(千葉大学園芸学部圃場)の気温の推定を行った.その結果,東京のデータは年間を通しかなり高温に経過し,生データの比較では問題があること,船橋の場合には観測点の特徴により特異な温度経過を示しているらしいこと,月平均・日平均気温に関しては重回帰式を使うことでかなりの精度で予測できること,日最高・日最低気温に関しては重回帰式を用いても必ずしも十分な精度で推定できず,物理的に詳細な状況を加味する必要があることが示された.

Physical soybean damages caused by fall of scoria with eruption of a volcano were experimentally studied. Scoriae were divided into three sizes. The small scoria is smaller than 1.5cmφ : the middle is 1.5 to 2.5 : the large is 2.5 to 3.5. These scoriae were fallen to soybean canopy from 5m above ground surface at three growth stages of soybean. Results are as follows. 1. Yield of all the damaged soybean decreased in comparison with the normal soybean. 2. The influence of the small scoria was less. The fall of leaves by the small scoria was hardly recognized in the late stage of growth. Damages by the middle scoria were especially large in the early stage of growth. Numerous leaves were fallen by the large scoria in the late stage of growth. When the pod is large, the yield is directly reduced by fall and injury of the pod in the stage. 3. Total fallen dry weight of soybean become very large by the large scoria in comparison with the middle scoria of the same weight. 4. Visible injuries of leaves in this experiment were similar to that observed in Izu Oshima just after the eruption of volcano in 1986.

Nighttime temperature is mainly determined by two factors. One is its altitude and the other is its topographical feature, surface condition or effects of sea. Therefore, to evaluate nocturnal cooling, we must remove altitudinal effect from nighttime temperature. In this study, we showed the way to evaluate cooling using temperature data from NOAA/AVHRR and numerical terrestrial data of Hokkaido-Island in Japan. Lapse rate of surface temperature for the meshes which had the highest temperature at the altitude, was equal to that of air temperature of atmosphere. Therefore we can calculate surface temperature without the altitudinal effect, by subtracting the estimated highest temperature of the altitude, from the real surface temperature. Thus, we defined the cooling of the mesh as the remainder temperature of the subtraction. Using the cooling, it was clarified that basins and Valleys are cooled more excessively than plains. © 1992, The Society of Agricultural Meteorology of Japan. All rights reserved.

The study was conducted to clarify the effects of cultural temperature on the activities of INA (ice nucleation-active) bacteria Pseudomonas syringae. INA bacteria were cuttured at 5 levels of temperature (0, 10, 20, 25 and 30°C) for 1 to 5 days of cultural periods respectively. The soybean leaflets contacted with the suspension of these INA bacteria cultured under above cultural conditions. The ice nucleation activities were evaluated through the freezing temperatures of water droplets suspended with INA bacteria and of soybean leaflets spread with INA bacterial suspension. There were no large differences between the freezing temperatures of water droplets suspended with INA bacteria cultured under the temperature condition of 20°C and below. However, the freezing temperatures of droplets suspended with INA bacteria cultured at 25 and 30°C decreased with the cultural duration. On the other hand, the freezing temperatures of soybean leaflets also dependent on cultural temperature, although they were generally lower than those of water droplets. The ice nucleation activities of the INA bacteria cultured under 25 and 30°C were almost nil. © 1991, The Society of Agricultural Meteorology of Japan. All rights reserved.

Hayakita, which is surrounded by hills like a basin, has strong stable air layers due to radiative cooling and is compared with Chitose which lies in the center of Yuhutsu plain. The Hayakita area also suffers from frost damage since low temperatures remain until early morning (Matsuoka et al., 1987). It was considered that the upper wind plays an important role in maintaining stable layers in Hayakita. In this study, relations between upper wind speed and surface wind speed were investigated. Wind speeds were measured at Hilltop as well as at Hayakita and at Chitose. The wind speed at Hilltop was compared with the upper wind speed which is at the 900mb isobaric surface, above Sapporo (V900). The analysis revealed i) Wind speed at Hilltop (UT) is greater than 2m/sec. ii) Wind speeds at 900mb and 800mb isobaric surface above Sapporo (V900 and V800 respectively) are greater than 2m/sec. iii) Vertical shear (│V900 — V800│) is less than 6m/sec. The regression equation between wind speed at Hilltop and at 900mb isobaric surface is given in eq. (1). The correlation coefficient (r) is significant to 1% level. Thus it may be stated that the wind speed at Hilltop represents upper wind speed at the 900mb isobaric surface. The relations between wind speed at Hilltop (UT) and, those at Hayakita and Chitose (UH and Uc respectively) were investigated on cloudy nights. It was considered that this type of situation, which was judged on the basis of 4-hour mean cloud amount being over 9.0 at the Chitose airport, has nearly neutral conditions aerodynamically. Eq. (2) shows relations between UT and UH, and, UT and Uc. The gradient of the regression line for Chitose is greater than that for Hayakita. From the relation between UH and Uc, eq. (3) was obtained using a hypothesis of logarithmic law of wind speed profile. The roughness parameters at Hayakita and Chitose were calculated to be 0.43m and 0.09m respectively, using the methods employed by Kondo and Yamazawa (1983). If this value at Chitose is substituted for Z0c in eq. (3), the roughness parameter at Hayakita (Z0H) is calculated to be 0.42m which is nearly equal to 0.43m as mentioned above. Thus roughness parameter (Z0) shown by eq. (3) can express topographical feature. On the clear nights which have below 2.0 of mean cloud amount, the relations between wind speed at Hilltop, and wind speed at Hayakita or Chitose resulted by eq. (4). These nights have stable conditions aerodynamically. The gradients of the regression equations are smaller than those under the neutral conditions, but the tendency that gradient at Chitose is greater than that at Hayakita, remains in eq. (4). The relationship between the time taken to destroy stable layers by entrainment and topographical feature, was investigated on the nights when there was wind speed increases at Hilltop. The crosscorrelation between the sequence of wind speed at Hayakita (or Chitose), and that at Hilltop was calculated for this analysis. Under steady state conditions, time taken to destroy stable layers (L) is represented as eq. (8). By inputting observed values into eq. (8), the regression equations are given in eq. (9). The regression constant at Hayakita (5=1.13) is larger than that at Chitose (5=0.96). The hypothesis that B is a unique constant for each location is justified. Thus, if regression equations such as eq. (9) are determined, we can predict the duration of low temperature periods using potential temperature gradient in the stable layer and upper wind speed. © 1988, The Society of Agricultural Meteorology of Japan. All rights reserved.

To research regional difference of frost damage, meteorological observations were made at Hayakita, located in the south-east of the Ishikari-Yuhutsu plain in Hokkaido. Hayakita has crops that are the most easily damaged by frost in the plain. In particular paddy rice plants are damaged by the first frost when their growth is retarded by a cool summer. The first frost in Hayakita occurs 1 week earlier than in other parts of the plain. To research this problem, Chitose that has different topography from Hayakita, was selected as a control area and some meteorological factors such as air temperature, wind speed, solar radiation, net radiation and downward radiation were compared between Hayakita and Chitose. These areas are at the same altitude and share similar surface features. Although Hayakita is surrounded by hills, Chitose is in the center of the plain and is located 12 kilometers away from Hayakita. In this paper, the daily minimum air temperatures and 4-hour mean values of the meteorological factors in the springs and falls of 1983 and 1984 were compared between Hayakita and Chitose. Also the variations of these factors on clear nights were compared. Daily minimum air temperatures in both seasons were not significantly different between Hayakita and Chitose. This means that the advection and accumulation of air mass cooled on surrounding slopes are not significant as causes of the frost damage in Hayakita. The 4-hour mean value of wind speed at Chitose was always greater than that at Hayakita. However, there were no significant differences for the other factors, such as solar radiation, net radiation and downward radiation between Hayakita and Chitose. The air temperature in Hayakita was often lower than that in Chitose, especially in the lower range of temperatures. This tendency was more remarkable in fall than in spring. Sometimes the temperature difference between the two regions reached approximately 5K in fall, accompanied with a large difference of wind speed. This large difference of air temperature tended to be observed from 20:00 to 4:00 of clear nights. It was caused by temperatures in Chitose often being rapidly increased by raising wind speed during that time, but both temperature and wind speed in Hayakita remained low and unchanged. When comparing temperature profiles to 80 meters above ground level of both regions, it was noted that the stable layer formed by radiative cooling was destroyed from upper portion to near ground surface at Chitose, while, on the other hand, only the upper portion of the layer was destroyed at Hayakita. However, both stable layers remained during the nights when no temperature difference occurred between the regions. Therefore, the occurrence of temperature differences between the regions is due to the difference in the destruction ratio of the stable layer. The phenomena mentioned above, often appeared in the center of the plain when the upper wind (geostrophic wind) speed and/or direction changed. The upper wind data were obtained from radiosonde data at the 900mb isobaric surface above Sapporo. The changes of wind were classified by following two patterns: i) upper wind speed very small at first, becoming stronger later, and ii) upper wind direction changing from a direction in which WSR (Wind Speed Ratio: the ratio of surface wind speed to upper wind speed at a direction) is small to other one in which WSR is greater. Greater WSR means greater wind speed at ground level for a given upper wind speed WSR is influenced by surrounding geographic features. Therefore, the WSR values at the center of the plain, lying between the high mountains to the east and west, were large for the north-south direction and small for the east-west direction. On the other hand, WSR values were relatively small for all directions in Hayakita. Thus wind speed in Hayakita was always smaller than that in the center of the plain. It can thus be recognized that low temperatures continue for long period at Hayakita because of the surrounding hills and that the frost damage at Hayakita occurs more easily than that in the center of the plain. The difference of temperature between Hayakita and Chitose is caused by the difference in the destruction ratio of the stable layers of Hayakita and Chitose. As this ratio is closely related to turbulent mixing determined by the upper wind speed (Kondo, 1982b), the complex topography contributes to the frost damage in Hayakita. © 1987, The Society of Agricultural Meteorology of Japan. All rights reserved.

In order to examine the effect of dew on the leaf surface on the freezing temperature T1of plant juice, the experiments were conducted by using the radiative cooling apparatus. When a pair of the primary leaves of a soybean seedling spread fully, the seedling was set in the apparatus and then cooled down to a subzero temperature. The mean freezing temperature of wet leaves 71w was —4.4°C and was 0.8°C higher than that of dry leaves T1das shown in Table 3. The difference in temperature was significant statistically. When one of a pair of leaves was dry and the other was wet, the wet leaf froze firstly and then the dry leaf froze within a few or longer seconds. The mean freezing temperature of the dry leaves T1dwwas — 3.9°C as shown in Table 4 and was 1.3°C higher than that of the dry leaves T1d (Table 3) as a result of ice inoculation by freezing of the wet leaf. The mean freezing temperature of the wet leaves T1ww was lower than T1dwas shown in Table 4. It is considered that this difference in freezing temperatures is due to the difference in evaporative cooling between the dry and the wet leaves under low humidity in the experimental cabinet. The multi-regression equation on the frost injury ratio/ the freezing temperature 7 and the minimum leaf temperature T3 after T1 (see Fig. 1) in the previous paper (Yamanaka et al. 1982) was modified by adding the present experimental data taken at the warmer experimental conditions than the former and the following equation was obtained. I = —8.21 T1-17.40 T3-34.26 In analyzing the experimental results, it was found that the frost injury did not occur when the plants were held in the supercooling condition or when the droplets on the leaves froze but plant juice did not freeze or only a part of liquid outside cells froze. © 1986, The Society of Agricultural Meteorology of Japan. All rights reserved.