Radiation Boundary Conditions in Numerical Modeling

Abstract

A two-dimensional anelastic model is used to study the propagation of errors arising from the use of open lateral boundaries. Reference experiments were performed using very large horizontal domains. Other experiments were carried out in smaller domains with various radiation boundary conditions. Direct calculation of the error fields demonstrates the mechanism for the generation, propagation, and growth of errors. It was shown that a fixed phase speed method resulted in runaway circulation while a floating speed scheme exhibited difficulties in regions where horizontal gradients in horizontal velocity are small. A hybrid scheme is proposed which was shown to work well in highly truncated spatial domains.