Shanshan Wei

Intercomparison and uncertainty analysis of global MODIS, cyclopes, and GLOBCARBON LAI products

Three major global moderate resolution leaf area index (LAI) products: MODIS/TERRA+AQUA (MCD15 C5), SPOT/VEGETATION CYCLOPES V3.1, and the GLOBCARBON V2.0, were compared in this study. Results show that the three products agree very well for grasses/cereal crops and shrubs. The products differ considerably for EBF, where GLOBCARBON shows systematically lower LAIs than MODIS (~1.02) and CYCLOEPS (~0.50). The discrepancies for EBF are attributed to the different LAI definitions and clumping corrections. MODIS and CYCLOPES generally agree with each other for DBF, ENF and DNF during the peak growth period. The product theoretical uncertainties, indicated by the quantitative quality indicators (QQIs), show that MODIS has the lowest uncertainty (0.19) followed by CYCLOPES (0.54) and GLOBCARBON (0.65).

Derivation of rice clumping index from time series MISR and MODIS directional reflectance data

Clumping index (CI) indicates the spatial distribution pattern of foliage. It is important for evapotranspiration (ET) and net primary productivity (NPP) estimation. Remote sensing methods offer an opportunity for CI estimation at the global scale. However, higher resolution and more stable temporal CI are critical for spatial and seasonal characteristic understanding of CI. In this study both 275 m MISR multi-angle reflectance product and 500 m MODIS BRDF parameter product were used for CI estimation. The CI map derived from MISR shows detailed information of spatial distribution and MODIS derived CI can effectively reflect the CI seasonal variation of rice and has good consistency with the variation tendency of field measurement CI. The combination of MISR and MODIS will help us better understanding the spatial and temporal characteristics of CI.