The quality of forecasts made with numerical prediction models degrades during the numerical integration due to systematic errors, that is, errors that are related to the model's formulation. Preliminary studies done with the Community Climate Model (CCM) of the National Center for Atmospheric Research (NCAR) indicate that horizontal resolution may be a critical factor in the evolution and structure of planetary scale waves which are simulated by the CCM. The goal of this research project is to determine the role of model resolution in systematic error. It will be accomplished through simulations of five winter periods and several forecast experiments. The results will have important implications for improving both extended range weather forecasts (up to 30 days) and climate models. This project represents a collaboration between Dr. T.-C. Chen, the principal investigator, and Dr. Joseph Tribbia, an NCAR scientist.