Validation of MODIS collection 6 FPAR/LAI in the alpine grassland of the Northern Tibetan Plateau

ABSTRACT Leaf area index (LAI) and fractional photosynthetically active radiation absorbed by vegetation (FPAR) are two important parameters in global carbon cycling. Ground measured LAI (LAIG) and calculated FPAR (FPARG) using LAIG were compared with three MODIS Collection 6 FPAR/LAI products (i.e. MOD15A2H derived from the Terra MODIS; MYD15A2H derived from the Aqua MODIS; and MCD15A2H derived from the combination of Terra MODIS and Aqua MODIS) in the alpine grasslands of the Northern Tibetan Plateau. MODIS FPAR/LAI showed significant positive correlations with FPARG/LAIG (coefficient of determination, R2 = 0.48–0.82). MOD15A2H, MYD15A2H and MCD15A2H LAI overestimated LAIG by 17%, 46% and 55% for fenced areas, and by 10%, 53% and 34% for open grazed areas, respectively. MOD15A2H, MYD15A2H and MCD15A2H FPAR overestimated FPARG by 24%, 37% and 44% for fenced areas and by 20%, 35% and 35% for open grazed areas, respectively. Our findings implied that Terra MODIS FPAR/LAI had the highest accuracy among the three MODIS FPAR/LAI products. The accuracies of MODIS FPAR/LAI also varied with land use types.

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