A Framework for Coupled Estimation of Evapotranspiration and Recharge Flux by Assimilating Remotely Sensed Land Surface Temperature and Soil Moisture Observation

The evapotranspiration and recharge fluxes are the link between the land's water and energy cycles. In-situ measurements of these fluxes are not suitable for large scale studies. The advancement of remote-sensing platform enables us to access different remotely sensed soil moisture (SM) (top 5cm) and land surface temperature (LST) products with good spatial and temporal coverage. These land surface state observations have implicit information on the partitioning of precipitation between evapotranspiration and recharge fluxes. A framework for coupled estimation of evapotranspiration and recharge fluxes using variational data assimilation (VDA) technique was introduced in this study. LST and top SM observations were assimilated into a coupled water energy balance model. The conceptual modelling framework was tested against synthetic dataset generated using Hydrus 1D model. The results show improvement in estimating evapotranspiration and recharge fluxes following the proposed data assimilation technique.