Abstract
An interpolation method was developed to estimate the 1km grid values of sunshine duration and solar radiation in Hiroshima Prefecture from the data observed at the AMeDAS stations distributed with a mean distance of about 21km. In the first step the influence of shading by the surroundings was removed from the average sunshine duration observed at the AMeDAS stations, and the duration without the influence of shading was estimated by the distance weighting interpolation in each grid. These values were converted to the values with the influence of shading by using the elevation data in the surrounding grids of National Land Numerical Information. Equation (6), which related sunshine duration to solar radiation, was derived to draw the solar radiation map. As an example of the application of our method, we drew the sunshine duration map for ripening period of rice plants and discussed their most suitable heading time taking into consideration the annual course of air temperature.
