Atmospheric Response to Tropical Thermal Forcing in Real Data Integrations

Abstract

Abstract Evidence is presented for a highly regular seasonal rearrangement of the long-wave pattern over North America from the winter to the spring. The change involves a reversal of the trough-ridge pattern between the two seasons wherein the anticyclone observed in the winter climatology over and west of the Rocky Mountains reverses to a spring trough, and the winter lee cyclone changes to a spring ridge over the eastern United States. These changes, which represent a westward shift of the long-wave pattern from winter to spring, are accompanied by westward shifts of the subtropical jet core from the east to the west coast, and of the tropical rain maxima from the Amazon Basin to the tropical East Pacific Ocean. We investigate the possibility that these westward displacements are dynamically related in a series of ten-day integrations of a general circulation model over four separate ensembles, each consisting of ten cases, during the winter and spring. The data for these ensembles is taken from the Gl...