Volume XLII-3
Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-3, 2041-2045, 2018
https://doi.org/10.5194/isprs-archives-XLII-3-2041-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-3, 2041-2045, 2018
https://doi.org/10.5194/isprs-archives-XLII-3-2041-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

  30 Apr 2018

30 Apr 2018

INFLUENCE OF SKY CONDITIONS ON ESTIMATION OF PHOTOSYNTHETIC PHOTON FLUX DENSITY FOR AGRICULTURAL ECOSYSTEM

M. Yamashita1 and M. Yoshimura2 M. Yamashita and M. Yoshimura
  • 1Tokyo University of Agriculture and Technology, Faculty of Agriculture, 3-5-8 Saiwai-cho, Fuchu, Tokyo, Japan
  • 2PASCO Corporation, PASCO Research Institute, 2-8-10 Higashiyama, Meguro-ku, Tokyo, Japan

Keywords: PPFD, PAR, Solar radiation, PAR fraction, Quantum-to-energy ratio, Diffuse ratio, Clearness index, Sky conditions

Abstract. Photosynthetic photon flux density (PPFD: µmol m−2 s−1) is indispensable for plant physiology processes in photosynthesis. However, PPFD is seldom measured, so that PPFD has been estimated by using solar radiation (SR: W m−2) measured in world wide. In method using SR, there are two steps: first to estimate photosynthetically active radiation (PAR: W m−2) by the fraction of PAR to SR (PF) and second: to convert PAR to PPFD using the ratio of quanta to energy (Q / E: µmol J−1). PF and Q/E usually have been used as the constant values, however, recent studies point out that PF and Q / E would not be constants under various sky conditions. In this study, we use the numeric data of sky-conditions factors such cloud cover, sun appearance/hiding and relative sky brightness derived from whole-sky image processing and examine the influences of sky-conditions factors on PF and Q / E of global and diffuse PAR. Furthermore, we discuss our results by comparing with the existing methods.