Estimation of energy fluxes from thermal infrared, spectral reflectances, microwave data and SVAT modeling

The ALiBi model, a Soil-Vegetation-Atmosphere Transfer model, was developed to simulate mass and energy exchanges between vegetation canopies, the soil and the atmosphere. In the present work, it was used in conjunction with remote sensing data in thermal, solar and microwave domains to assess energy balance of various vegetation canopies (two soybean crops, one wheat crop and one fallow canopy). Inversions of radiative transfer formulations were performed to retrieve model parameters: -i) canopy structure parameters (leaf area index and canopy height) from red and near-infrared reflectances, when available; -ii) surface soil moisture from microwave measurements, when available and -iii) plant water transfer parameters from thermal infrared measurements. The estimates of energy balance fluxes were in good agreement with measured values, in particular for well-developed canopies. It can be noticed that it was not necessary to know accurately surface soil moisture and leaf area index to assess energy balance fluxes. Conversely, the vegetation height must be known with a good accuracy.