GCM Simulation Studies on the Relative Importance of Wind Observing Systems for Numerical Weather Prediction

Two series of simulation experiments were conducted with the GLAS Fourth Order GCM to assess the information content of different observing systems capabilities to infer atmospheric states. In the first set of experiments, the "natural atmosphere" from which simulated observations were derived is a long integration of the model. In the second set of experiments, simulated observations were extracted from the NMC operational analysis for the FGGE Special Observing Period - 1. In both cases, the observations consisted of complete 3-dimensional fields of either winds, temperatures or surface pressure. These observations were then used to run a 12 hour analysis/forecast cycle and the ability of the observations to infer the other unobserved fields was determined from the (asymptotic) 12 hour forecast errors.