In paddy rice production areas in Hokkaido, forest windbreaks were established to improve environmental conditions and protect rice plants from damage during cool summer weather. We measured meteorological variables, water temperature and rice growth at four sites at distances of 3H, 5H, 10H and 17H (H is the windbreak height of 18 m) leeward from a forest windbreak that stretches east-southeast to west-northwest. The 17H site was a reference site where the windbreak had little influence. The following effects of the windbreak were observed in sites 3H, 5H and 10H. Wind speed was reduced when the wind direction was between the south and west, which was the most frequent wind directio in June and July in this area, including in cool summer years. Air temperature increased/decreased during the daytime/nighttime, respectively, but daily average air temperature was little changed. Daily mean water temperature increased in June but decreased in July. A possible reason of this was that higher water temperatures in June hastened leaf expansion resulting in a smaller amount of radiation being transmitted to water surface in July. Although plant height and radiation interception increased earlier, their maximum values showed little difference from the reference site. There was no significant difference in the yield among the sites. Although no damage from cool summers occurred in our study years, our results show the possible mechanisms by which windbreaks can reduce damage to rice from cool summer weather. Windbreaks did not warm air or water temperatures in the booting stage in middle to late July and offered little protection effect then. However, it is known that cool water temperatures before panicle initiation, corresponding to the June period, increases the susceptibility of panicles to low temperatures in the booting stage, causing sterility. Higher water temperatures in June due to windbreaks would, therefore, reduce sterility in cool summers.
Meteorological data are one of the fundamental information not only for studies on agricultural meteorology but also for other research fields and various social and economic activities. In this review, I summarized the current status of broad-scale (i.e. landscape or larger) data of land-surface meteorology applicable to agrometeorological works. The data sets presented here include statistically aggregated or up-scaled data, objective analysis and reanalysis data with meteorological models, teleconnection indices, satellite remote sensing data, and synthetic data for model input. Based on the development of weather monitoring systems and informatics, variety, quality, and coverage of these data sets have greatly improved in last decades. The data development facilitates our researches and operations in agricultural fields with respect to yield estimation, meteorological risk avoidance, optimization of management, and so on. However, we should still pay enough attention to deficiencies (e.g., bias and error, and short coverage) contained in these data, including the characteristics and difference among data sets, and data use policy.
Flux study has in an important position in earth science today. Pioneering flux studies were considered to learn the background of the todays’ prosperity, the philosophy and methods of pioneers for the next progress. Dr. Eiichi Inoue developed “Turbulent Eddy Model” to reveal the mechanism of turbulent structure of wind near the ground. The model was composed of mean flow and many ranks of eddies, Largest, Medium, and Smallest turbulent eddies, those were assumed as mutual actions among them such as Stokes’ friction. The model provided the eddy-energy spectrum of -5/3 power law, by the assumption of the same energy dissipation among all ranks of eddies (Inoue, 1951, in Japanese). Those were approved by applications of observed natural wind data. Inoue paid attention to the interaction between the waving plant phenomena “Honami” and wind, and the logarithmic function over plant canopy was also derived from the model analysis. Investigation of Honami with the model provided zero-plane displacement, roughness length, and the diffusion coefficient over plant canopy, resulted in establishment of the flux calculation method “Gradient Technique”. Inoue and the colleagues applied their profile data of wind, temperature, water vapor, and CO2 to Gradient Technique and succeeded to determine fluxes at first in the world (Inoue et al., 1958, in Japanese). Today, we can get the field observed fluxes automatically with quality control and we believe them as the true reflection of the nature unconditionally. However, the great efforts by pioneers to understand the figure of truth using limited data suggested us to examine the data carefully and confront the object in nature. Contents were presented at the organized session of the 75 years Anniversary Meeting of SAMJ, on March 13, 2018.
Potatoes grown in Kami-Yuchi district, the northernmost hilly part of Hokkaido, Japan, were well known and popular for their delicious taste. They were called "Yuchi-potato". However, farmers gave up their cultivation 60 years ago after the introduction of dairy farming in the district. Some farmers have recently tried to revive Yuchi-potato production, thinking that meteorological conditions in the district are favorable for high quality potato production. We examined this perception as follows. We compared normal values of meteorological factors in Kami-Yuchi district with those in other potato-producing areas of Hokkaido (Nayoro, Kitami, Biei, Kutchan and Memuro). Precipitation is within a suitable range. Although sunshine hours in Kami-Yuchi are moderate among the compared areas, there are many total sunshine hours in the growing season. This is because of a long growing season caused by the low temperature. Although the diurnal range of air temperature in Kami-Yuchi is smaller than those in Biei and Nayoro, the temperature in Kami-Yuchi (maximum, minimum, mean, nighttime in a day) is lowest, particularly in low-altitude locations along rivers, which could rise starch value.
This study developed a farmland meteorology estimation system to support precise cultivation management. The system is suitable for application even in areas of hilly, mountainous, or sloping terrain. This system provides daily maximum, minimum, and mean air temperatures, daily relative humidity, and daily accumulations of solar radiation, reference evapotranspiration, and precipitation, together with 6-hourly predictions of precipitation. These data are estimated from the Automated Meteorological Data Acquisition System (AMeDAS) observation data without any observation devices except for the precipitation data. Precipitation data is just an Analysis and Forecast of Precipitation produced by the Japan Meteorological Agency. The estimation methods used for air temperature and solar radiation are based on original techniques developed by the National Agriculture and Food Research Organization. Air temperature data are estimated by a model that uses a radiative cooling scale to determine temperature differences between estimation sites and an AMeDAS site. Solar radiation data constitute the sum of direct and diffuse solar radiations; the former are estimated using a model of atmospheric transmittance and the latter are estimated using models for dimensionless parameters of direct and diffuse solar radiation. Other meteorological data are estimated according to the Irrigation and Drainage Paper No. 56, produced by the Food and Agriculture Organization of the United Nations. An automated device for the acquisition of air temperature has also been developed for the temperature difference estimation model. This device acquires data with similar accuracy to AMeDAS without needing an AC power supply.