A series-scheme surface-renewal method within a two-source energy-balance framework

A new technique, based on Surface Renewal (SR), was developed to explain the contribution of the soil and the vegetation of the sensible heat flux. It was compared to the original Two Source Energy Balance (TSEB) model based on series scheme. The methodology to partition the components of the radiation, the soil heat flux and the latent heat flux for the soil and vegetation were identical to the original model, however, the SR concepts were implemented to estimate the sensible heat flux over sparse canopies. The key point was to model the temperature of the macro-parcel of air during the quiescent period. The input requirements are the same as the original model. The TSEB model was tested half-hourly under clear sky conditions and unstable cases for two growing crops (rain-fed soybean and corn using 12 and 14 samples, respectively) with canopy heights ranging from 0.2 to 1.8 m (estimated fraction of ground canopy cover was from 39 % up to 97 %). The land surface temperature (retrieved from Landsat 5 and 7) was used to partition soil and canopy temperatures. The eddy covariance (EC) method and the surface energy balance closure using the Bowen ratio (BR) method (estimated using the EC method) they both were taken as a reference. Regardless of the reference and crop, the results (linear regression analysis, the RMSE and the index of agreement, AI) obtained were comparable, or slightly better using the SR methodology (the AI ranged between 92 % (soybeans using the EC method) and 98 % (corn using the EC method) for SR and 83 % and 94 % (soybeans and corn, respectively, both using BR method) for the original method).