Validation of the Feasibility of MOD16 Algorithm for Estimating Crop Field Vapor Flux in North China Plain
MODIS水汽通量估算方法在华北平原农田的适应性验证

The MODIS product of the land surface vapor flux (MOD16) is not yet released by NASA because some parameters in the algorithm are very unstable in the time and space scales, which are difficult to be or cannot be derived from the remote sensing data. In this study, we validated the original algorithm of MOD16 with the ground measured data from April to May in 2002 (Yucheng Ecological Experimental Station in Shandong, CAS). The result showed that the estimated vapor flux was about 20% more than the observed values. We revised the original model by adjusting the crop physiological temperature parameters and coefficients for calculating the aerodynamic resistance, and the fractional vegetation cover according to the characteristics of winter wheat in Yucheng Station. The slope of the regression line plotted with the result simulated by the revised algorithm and the field measured data was 0.9706, and the correlation coefficient (R 2 ) was 0.8845, which means that the vapor flux simulated by the revised algorithm became more close to the measured data. The result implies that we can apply the revised method to the estimation of the crop field vapor flux in a regional scale by using MODIS data.