Comparison of ENVISAT RA2 backscatter results over global land surface

Unlike ERS1/2 and JASON1, ENVISAT RA2 provides the backscatter coefficient from four retrackers (Ocean, Ice1, Ice2, Sealce), which is useful to study the behavior of RA2 backscatter over land. This paper presented an analysis of RA2 four Ku band backscatter performance over global, especially over vegetated area, and provided a detailed comparison with JASON1 data. The temporal evolution of the RA2 backscatter coefficients was evaluated for main vegetation type (ENF, EBF, DNF, DBF, mixed forest, croplands, savannas, grasslands) from October 2004 to June 2009. Results indicated that SigmaO values from four retrackers show large variability. The backscatter of Ice1 and Sealce retrackers are systematic larger than that of the Ocean and Sealce. The inter-comparison with JASON1 showed that the greatest degree of correlation of the RA2 SigmaO with JASON1 is obtained with Ice1 and Sealce.