Development of Spatial Distribution Maps in a Grid of 50 m for Weather Resources Using the Weather Data of an Agricultural Network System in Conjunction with the Geographical Factors

摘要

Due to periodic attacks of a cool and foggy wind in northern part of Japan, caused by an Okhotsk high pressure and sometimes bringing serious rice crop damage, the farmers in southeast area of Aomori Prefecture, the north end of the main island, organized the 14 JAs (Japan Agriculture Cooperatives). They built an agricultural information network system in 1994 for providing information on weather predictions, markets, production technologies, and workers to 4,500 farms to help their agricultural business. In this study, we developed spatial distribution maps in a grid of 50 m for weather resources using weather data from the 28 weather stations of the system in conjunction with geographical features where the system locates on. The maps of weather resources were analyzed in the area of 40 km in width by 80 km in length. Four weather factors were chosen as the mean daily air temperature, the maximum and the minimum daily air temperatures. The weather data were collected during from Jan 1997 to Dec 2000. The 18 geographical factors such as altitude, latitude, longitude, and gradient were obtained from a digitalized altitude map in a grid of 50 m provide by the government. A multiple regression analysis between each weather factor and its optimal geographical factors was examined in combination with the stepwise method. As optimal geographical factors, 3 to 5 factors were determined for each weather factor, resulted in a high determination coefficient of more than 0.80. When a cool and foggy weather caused by an Okhotsk high pressure was occurred in summer, the maps of the mean daily air temperature was affected strongly by the geographical factor of the slope to east direction. In a Fourier analysis of altitude distribution, the optimal grid size for the maps was estimated in a range of 50 m to 30 km.