[ACG36-P27] Development of the LAI and FAPAR product using GCOM-C/SGLI data
Keywords:LAI, fAPAR, GCOM-C, MODIS
The Japan Aerospace Exploration Agency (JAXA) launched the Global Change Observation Mission - Climate (GCOM-C) satellite last December. We have been developing one of the GCOM-C standard land products, the Leaf Area Index (LAI) and the fraction of Absorbed Photosynthetically Active Radiation (fAPAR) product. In this document, we introduce the current situation for producing LAI and fAPAR product using SGLI data.
The LAI is defined as one half of the total green leaf area per unit ground surface area. In the GCOM-C product, LAI was estimated for overstory leaf. The information for understory vegetation is added as understory NDVI. The fAPAR is defined as the proportion of the effectively absorbed solar radiation by plants in the photosynthetically active wavelengths (the spectral region from 400 to 700 nm).
LAI and fAPAR were estimated based on the look-up tables showing the relationships between the multi-angle atmospherically-corrected land surface reflectance data and the LAI or fAPAR. The look-up tables were produced for the 6 kinds of land covers and various geometry conditions. They were adjusted to fit with the field-observed reference data collected from literatures.
The relationships between LAI/fAPAR and surface reflectance data at the top of canopy were simulated using a radiative transfer simulator, the Forest Light Environmental Simulator (FLiES) [1]. It simulates radiative transfers in the forests and grasslands based on the Monte Carlo method.
The accuracy of the retrieved LAI and fAPAR will be assessed using the in-situ observation data which will be collected at several sites on global this year. In this research, the MODIS surface reflectance data were used for the satellite data for producing the look-up table. The look-up table is revised to fit with the SGLI data.
[1] H. Kobayashi et al., 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 (2008), 173-185.
The LAI is defined as one half of the total green leaf area per unit ground surface area. In the GCOM-C product, LAI was estimated for overstory leaf. The information for understory vegetation is added as understory NDVI. The fAPAR is defined as the proportion of the effectively absorbed solar radiation by plants in the photosynthetically active wavelengths (the spectral region from 400 to 700 nm).
LAI and fAPAR were estimated based on the look-up tables showing the relationships between the multi-angle atmospherically-corrected land surface reflectance data and the LAI or fAPAR. The look-up tables were produced for the 6 kinds of land covers and various geometry conditions. They were adjusted to fit with the field-observed reference data collected from literatures.
The relationships between LAI/fAPAR and surface reflectance data at the top of canopy were simulated using a radiative transfer simulator, the Forest Light Environmental Simulator (FLiES) [1]. It simulates radiative transfers in the forests and grasslands based on the Monte Carlo method.
The accuracy of the retrieved LAI and fAPAR will be assessed using the in-situ observation data which will be collected at several sites on global this year. In this research, the MODIS surface reflectance data were used for the satellite data for producing the look-up table. The look-up table is revised to fit with the SGLI data.
[1] H. Kobayashi et al., 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 (2008), 173-185.