Combining observations in the reflective solar and thermal domains for improved mapping of carbon, water and energy fluxes

This study investigates the utility of integrating remotely sensed estimates of leaf chlorophyll (C_ab) into a thermal-based Two-Source Energy Balance (TSEB) model that estimates land-surface CO₂ and energy fluxes using an analytical, light-use-efficiency (LUE) based model of canopy resistance. Day to day variations in nominal LUE (LUE_n) were assessed for a corn crop field in Maryland U.S.A. through model calibration with CO₂ flux tower observations. The optimized daily LUE_n values were then compared to estimates of C_ab integrated from gridded maps of chlorophyll content weighted over the tower flux source area. Changes in C_ab exhibited a curvilinear relationship with corresponding changes in daily calibrated LUE_n values derived from the tower flux data, and hourly water, energy and carbon flux estimation accuracies from TSEB were significantly improved when using C_ab for delineating spatio-temporal variations in LUE_n. The results demonstrate the synergy between thermal infrared and shortwave reflective wavebands in producing valuable remote sensing data for monitoring of carbon and water fluxes.