Laterally forced equatorial perturbations in a linear model. Part I: stationary transient forcing

Abstract

Atmospheric equatorial perturbations generated by extratropical transient forcing are simulated numerically in a linear model. Impacts of mean zonal wind on such lateral forcing processes are emphasized. The extratropical forcing source is stationary and localized, with its amplitude varying with time. This forcing configuration simulates atmospheric events that may intrude into the tropics from the extratropics, such as the cold surges during the Asian winter monsoons and the deep midocean troughs. For forcing of large time scales (≥4 day), the equatorial responses are completely dominated by the Rossby mode component. When the forcing time scale is one day or smaller, the major components in the equatorial perturbations are the Rossby, westward mixed Rossby-gravity, and Kelvin modes. -from Authors