A Fourier Series Approach to Skyline Generalization for Surface Irradiance Estimates in Alpine Terrain

Abstract

The degree of generalization acceptable in defining alpine skylines in radiation budget components is explored using truncated Fourier series representations. Numerical simulations are performed for sites in the Teton range of Wyoming, U.S.A. The mean skyline approach performs poorly for all irradiances except the incoming longwave. To calculate direct and global solar and net radiation, more complex skylines are needed with several harmonics, although the requirements are less stringent if primary interest is focused on spatially-averaged radiation budgets. Nevertheless, the Fourier series approach shows promise as a means of reducing storage requirements for skyline data in computer programs to perform topoclimatic radiation calculations and as a method of generating conveniently and objectively a continuous skyline function from discrete data.