The OSSE Framework at the NASA Global Modeling and Assimilation Office (GMAO)

Observing System Simulation Experiments (OSSEs) refer to data assimilation experiments where simulated observations are used in place of real observations. In the OSSE experiments, observations are simulated using atmospheric state variables from a free-running NWP model, known as “nature”, and forward operators, e.g., a radiative transfer model for simulating satellite radiances. Since the truth, the nature, is perfectly known for the OSSE experiments, OSSEs can be used for a large variety of experiments including evaluating the impact of observations from new instruments on analysis and forecast skills, as well as for evaluating new data assimilation techniques.

This abstract summarizes the OSSE framework developed at the Global Modeling and Assimilation Office at the National Aeronautics and Space Administration (NASA/GMAO). Some of the OSSE techniques developed at GMAO including simulation of realistic observations, e.g., adding errors to simulated observations, are now widely used by the community to evaluate the impact of new observations on the weather forecasts. This talk presents some of the recent progresses and challenges in simulating realistic observations, radiative transfer modeling support for the GMAO OSSE activities, assimilation of OSSE observations into data assimilation systems, and evaluating the impact of simulated observations on the forecast skills.