Effects of Weather and Ground Surface Conditions on Solar Radiation Components

抄録

Special observations of solar radiation have been carried out in the northern side of central Japan. Using the data, Seasonal variation, geographical distribution and the relationship between solar radiation components and weather were obtained. The topographical features of the measurement stations were divided into two regions for solar radiation components.
The annual progression of total and direct solar radiation was characterized by a curve with two depressions in the rainy and snowy Seasons. The fraction of Photosynthetically Active Radiation (PAR, 395-715nm) in total solar radiation was large over in the Japan Sea region, though it was small over the the mountainous region.
The three atmospheric turbidity indices of Linke's turbidity factor, Tu, the mean extinction coefficient, a, and Berlyand's f-coefficient were estimated for clear days. Tu, a and f were slight in the the winter and large in the summer, and these values in the mountainous region were smaller than they were in the Japan Sea region. The relationships between precipitable water, three turbidity indices and PAR components were estimated by a simple proportional relation, respectively.
The effects of snow cover and clouds on total solar radiation were calculated. Under snow cover conditions, daily total solar radiation increased by about 10% on clear days and about 15-55% on cloudy days.