Validation of MODIS LAI Product Using Upscaling Sentinel-2 Decameter-Scale LAI and Field Measured LAI

Leaf area index(LAI), defined as half of total leaf area per unit ground surface area, is a critical structural parameter. The objective of this paper is to validate MODIS LAI product(MOD15A2H) using decametric-scale sentinel-2 LAI and field measured LAI. The research was conducted in Yucheng station and the main crop types in Yucheng site are winter wheat and summer maize. After atmospheric correction and Snap software process, we obtain S2(Sentinel-2) 10m resolution LAI. The S2 10m LAI was validated by comparing with field measured LAI. The S2 10m LAI showed good agreement with field measured LAI(R
²
= 0.81, RMSE = 0.6). To convert the S2 10m LAI to the same 500m spacial resolution with MOD15A2H, we proposed a MODIS-Like upscaling method, the Sentinel-2 500m LAI was obtained. The MOD15A2H showed very good agreement with Sentinel-2 500m LAI(R
²
= 0.96, RMSE = 0.23). However, the comparison result of field measured LAI and MOD15A2H(R
²
= 0.68, RMSE = 0.58) was poor. Finally, we analyzed the time series of field measured LAI, sentinel-2 10m LAI, sentinel-2 500m LAI and MOD15A2H LAI.