The Reproducibility of Gross Primary Production Estimation From GPP Capacity and Canopy Conductance Index in Dry Area

The characteristics of this GPP estimation method correspond to the photosynthesis process. The photosynthesis velocity depends on itś capacity and depression because of weather conditions. The depression part is controlled by the stom-atal opening and closing and the canopy conductance was calculated using Big-leaf model. From model calculation, the fist highest contribution of canopy conductance's denominator was VPD, and that of numerator was evapotranspiration. In the period of around noon, evapotranspiration was not changed drastically. In the period, the canopy conductance index was considered as the slope of 1/VPD changing as time. In dry area, the surface temperature of around 11 a.m. and 1 p.m. was strongly correlated with VPD of 11 a.m. and 1 p.m., respectively. From this results, it is considered that the slope of 1/VPD changing estimated from surface temperature is one candidate of canopy conductance index. In this study, reproductivity of GPP using the estimation algorithm was examined. From the results, the tendency of GPP changing of the satellite observing times was recalculated using GPP capacity and conductance index. Although when the time of staring daytime depression was earlier than 11 a.m., the amount of depression was underestimated.