Exploring the potential of solar-induced fluorescence for terrestrial evapotranspiration estimation

Terrestrial evapotranspiration (ET) is a significant part of the hydrological cycle and it couples water cycles and carbon cycles. Accurate ET estimation is of great significance to hydrological prediction. Recently, the widely used solar-induced fluorescence (SIF) for photosynthesis estimation purpose has been applied to estimate ET given the tight coupling of water and carbon cycles. Some studies have shown that SIF has the potential to predict ET when combined with other meteorological variables. However, these ET-SIF researches in the past are mostly based on empirical relationships between ET and SIF but rarely rely on the mechanistic process of carbon-water interactions. The water and carbon cycles are naturally coupled via plants’ stomata, through which plants exchange CO2 and H2O with the atmosphere. Thus, the main objective of our research is to develop SIF-based ET estimation models by coupling the water and carbon cycles. The model estimates ET by combining SIF with remote sensing products like leaf area index (LAI), photosynthetically active radiation (PAR) and vapor pressure deficit (VPD). The model is well validated by the FLUXNET2015 tower-based ET and MODIS16 ET products.