Observing systems simulation experiments

This report deals with a particular class of simulation experiments - those designed to evaluate the use of data from a given observing system in numerical weather analysis and forecasting. Simulation of data is an attractive option when evaluating a proposed observing system for which no real data are yet available, or when the experiment requires reference to atmospheric observations that can be considered perfect. This report provides an overview of the use of observing systems simulation experiments (OSSEs) in meteorology. We discuss the reasons that OSSEs have been employed. The history of OSSE applications is summarized, the apparent limitations of the method are listed, and future prospects of OSSEs are discussed.