Transients and the extratropical response to El Nino

A baroclinic stationary wave model linearized about a zonally symmetric flow is used to interpret the extratropical atmospheric response to El Nino produced by a general circulation model. The direct response to anomalous diabatic heating is found to be small in the extratropics; the dominant term is the response to the anomalous transients, particularly the anomalous upper tropospheric transients in the vorticity equation. One can distinguish between two distinct parts of the response of the transients to the tropical heating: the movement of the Pacific storm track associated with the anomalous extratropical wave train, and changes in the penetration of Rossby waves into the tropics resulting from the modified tropical winds. -from Authors