QUANTIFYING SOUTHERN OSCILLATION-PRECIPITATION RELATIONSHIPS FROM AN ATMOSPHERIC GCM

This paper is an extension of a study by C. Ropelewski and M. Halpert, which examines observed precipitation relationships with the Southern Oscillation. Here, the authors repeat their analysis using atmospheri c general circulation model precipitation from the average of a 13-run ensemble. The GCM is the atmospheric component of the coupled model u sed for seasonal prediction at the National Centers for Environmental Prediction, except that in this study, the observed sea surface temper atures were specified for the ensemble runs. Results are compared and contrasted with the observed Southern Oscillation-related precipitatio n behavior. These comparisons show that the multiple ensemble simulati ons compare favorably to the observations for most areas in the Tropic s and subtropics. However, outside of the deep Tropics, the model simu lations show large shifts or biases in the location of the Southern Os cillation-related anomalies. In particular, anomalies shown by the obs ervations to occur in the southeastern United States are shifted westw ard in the simulation.