A study on the radiative transfer parameterization scheme within canopy in land surface process model.

A four-stream solar radiative transfer model within canopy in land surface process model was developed. The four-stream approximation method of atmospheric radiation equation is used to gain the analytic solutions of the basic equation of radiative transfer within canopy. The fourstream solar radiative transfer model within canopy is based on the two-stream short wave radiative transfer model. The radiative transfer theory within canopy is based on the radiative transfer theory in atmosphere. Each parameter of the basic equation of canopy has the special geometry and optical character of leaf or canopy. The upward or downward radiative fluxes are related to the diffuse phase function, G function, leaf reflectivity and transmission, leaf area index, and solar altitude angle of incident beam. The computed results of the albedo of canopy on the condition of horizontal leaf from new developed four stream radiative model within canopy and the original two stream model are compared, and the four-stream model is proved to be successful by the same modelling results of the canopy albedo of the any solar incident angle. The paper carries out one experiment to evaluate the simulations of the land surface model simultaneously coupled with the both radiative transfer models. The test indicates that the simulation of land surface process model coupled with four-stream model is better than twostream radiative transfer model, since the computed solar radiation absorption of land surface is closer to the observation.