Development of a global LAI/ FAPAR estimation algorithm for JAXA's new earth observation satellite,GCOM-C1

Japan Aerospace eXploration Agency (JAXA) is planning to launch a new earth observation satellite, GCOM-C1 (Global Change Observation Mission 1st-Climate) in the Japanese Fiscal Year 2016. SGLI (Second generation GLobal Imager) is a radiometer, which has 17 channels from near ultraviolet to thermal infrared. Furthermore, it has the features, such as 250m spatial resolution, polarization, and multi-angle observation. In the GCOM-C1 land science team, vegetation index, above ground biomass, LAI (Leaf Area Index), FAPAR (Fraction of Absorbed Photosynthetically Active Radiation), etc. are scheduled to be generated from SGLI data as standard products. These are important in order to estimate terrestrial carbon cycle. In this study, we propose a new LAI and FAPAR estimation algorithm from SGLI data and the proposed algorithm was applied to Terra/ MODIS data. The relation between LAI and BRF (Bidirectional Reflectance Factor) in red and near infrared bands or FAPAR are dependent on crown cover ratio. Therefore, LUT (Look Up Table) of crown cover ratio, LAI and BRF in red and near infrared or FAPAR are created by FLiES which is 3-dimensional radiative transfer model (Kobayashi, H. and H. Iwabuchi (2008), A coupled 1-D atmosphere and 3-D canopy radiative transfer model for canopy reflectance, light environment, and photosynthesis simulation in a heterogeneous landscape, Remote Sensing of Environment, 112, 173-185). First, crown cover ratio is estimated from multiple land surface reflecntace in red and near infrared bands based on LUT of BRF in red and near infrared bands. Next, LAI and FAPAR are estimated from land surface reflectance in red and near infrared band based on estimated crown cover ratio and LUT of BRF in red and near infrared and FAPAR. As a result of applying Terra/ MODIS land surface reflectance product (MOD09), estimated LAI and FAPAR agreed with LAI and FAPAR observed at the AmeriFlux sites.