Spectral viscosity for shallow water equations in spherical geometry

A spherical spectral viscosity operator is proposed as an alternative to standard horizontal diffusion terms in global atmospheric models. Implementation in NCAR's Spectral Transform Shallow Water Model and application to a suite of standard test cases demonstrates improvement in resolution and numerical conservation of invariants at no extra computational cost. The retention in the spectral viscosity solution of high-wavenumber information allows the successful application of high-resolution postprocessing methods.