Application of 3D Radiative Transfer to Mountains
| Chen, Yong | UCLA |
| Hall, Alex | University of California, Los Angeles |
| Liou, Kuo-Nan | UCLA |
A large part of the land surface is not flat, but vertically structured. In mountain terrain, accurate calculations of the net radiation for slopes of varying gradient and orientation are of considerable importance in determining the energy budget of the surface. In order to evaluate the surface variations of total solar irradiance, it is necessary to calculate the direct, diffuse and terrain-reflected components. A 3D Monte Carlo radiative transfer model has been developed and applied to mountain surfaces to study the diurnal and seasonal changes in surface fluxes by choosing 9 different solar zenith angles, including noon, sunrise+1/2 hour, sunset-1/2 hour, and three cases between solar noon and sunrise/sunset, on the 21th of each month over a large scale mountain area. The area located within a rectangular box from about 48-490 N latitude and 119.5-1210 W longitude was chosen as the research domain. It is away from the coast, has a high elevation (3 km), and varies in slopes and orientations. We investigate the effect of the rugged terrain on the radiation field for clear sky. The surface topography information is taken from the HYDRO1K data set. Each pixel of the DEM (digital elevation model), which is completely described by the elevation of its center point and a unitary vector orthogonal to its surface, is associated with a spectral bidirectional reflectance model. The difference between the incoming surface solar radiation for a flat surface with the same mean height as the mountain and the incoming surface solar radiation averaged over the domain have been used to investigate the significance of 3D topographical radiative transfer in reference to the conventional radiation schemes. Results will be presented in the poster.
This poster will be displayed at the ARM Science Team Meeting.