S&p 500(0): Utilizing Hierarchical Bayesian Modelling to advance parameter estimation of Canopy Interception Models using Eddy Covariance, Throughfall and Soil Hydraulic Measurements in a Mediterranean Ecosystem

The interception of rainfall by a surface, such as vegetation and soil, reduces the quantity of water participating in downstream processes. This rainfall interception loss is a non-negligible quantity that varies with the ecosystem, meteorological, and rainfall conditions. Rainfall interception models are needed to incorporate the three properties to estimate interception loss. However, the interception losses from these models are rarely validated directly. Rather their validation relies on the residual of the water balance. Eddy Covariance (EC) towers measure the fluxes of water vapour and present an opportunity to validate the modelled interception losses.

We present a pioneering interception study that compares evaporation from physically calibrated interception models to the energy balance closure corrected water vapour fluxes recorded intermittently by an EC tower. We generate parameters for the canopy interception models by the hierarchical Bayesian treatment of the Rutter, Rutter sparse, Gash, and Calder models with the data from automatic throughfall and rain gauges over 271 rain events (177 for Gash). We use these models to estimate the extent of soil cover, throughfall to the soil underneath the canopy, and interception losses. A physically calibrated soil evaporative capacitor model was then used to model the evaporation from the bare soil and soil beneath the canopy. The canopy interception models recreated the event-wise throughfall well, however they did not represent a substantial improvement on the benchmark of a simple percentage estimate. The combined soil and canopy model is considerably better than a simple percentage in recreating the magnitude and time series of interception loss. The method developed can be applied to any EC tower that measure throughfall allowing for broader insights to be generated into the capability and limitations of interception loss modelling.