Orography Blending in the Lateral Boundary of a Regional Model

Abstract

A simple method to employ an orography blending technique near the lateral boundary of the regional model is proposed. The method blends the orography of the regional model on the lateral boundary with that of the global or coarser resolution regional model. This method is tested in the NCEP Regional Spectral Model. A long-range prediction experiment of one month?s duration is conducted in the East Asian region. It is found that the proposed method provides regional model forecasts consistent with the global model forecasts without a discernible systematic bias. It is likely that modifying the regional model orography following the values of global model or analysis data is more efficient than elaborating the numerics of a lateral boundary scheme to eliminate systematic error.