Abstract
In order to investigation the effect of radiation reflected from the sea on the spectrum of diffuse radiation at the canopy of orchard, spectral radiance of the sea, sky and canopies of orange orchard were measured with a spectrophotometer on the slope facing to the sea. Diffuse spectral irradiance on the sea side of the canopy was also measured.
The spectral pattern of the radiance of the sea was similar to that of the sky; photosynthetically active radiation (PAR, 400-700nm) dominated to near infrared radiation (NIR, 700-1100nm). In the radiance of the canopy, however, NIR dominated. PAR in diffuse radiation reaching the canopy was enriched more by the reflected radiation of the sea than by that of the canopy. The radiance of the sea reached its maximum near sunset when the reflection became specular. PAR in diffuse radiation at the canopy was greater by 8.7% at the high elevation (240m above sea level) that at the low elevation (110m). The corresponding shape factors of the sea for the high and low elevations which were calculated based on photographs were 0.072 and 0.048 respectively, suggesting that PAR in diffuse radiation on slope could be reflected as a function of a shape factor of the sea.
The enrichment of PAR in diffuse radiation by the reflected radiation of the sea may suggest the light condition of the orchard on the slope facing to the sea would become favorable for photosynthesis.
