A GCM Simulation of the Relationship between Tropical-Storm Formation and ENSO

Abstract A low-resolution Geophysical Fluid Dynamics Laboratory (GFDL) general circulation model has been integrated for 15 years. In the course of this experiment, the observed month-to-month sea surface temperature (SST) variations in the tropical Pacific Ocean were incorporated in the lower boundary condition. The output from this model run was used to investigate the influence of El Nin-Southern Oscillation (ENSO) events on the variability of tropical-storm formation. Criteria for detecting tropical cyclogenesis and tropical-storm formation were developed for the model. Tropical storms appearing in the model atmosphere exhibit many typhoonlike characteristics: strong cyclonic vorticity and convergence in the lower troposphere, strong anticyclonic vorticity and divergence near the tropopause, and intense precipitation. It is demonstrated that, despite its coarse resolution, the model is capable of reproducing the observed geographical distribution and seasonal variation of tropical-storm formation. The...