Resumen
The zonal state of the atmosphere is reconsidered using interaction coefficients to simulate the interplay between the atmospheric waves and the zonally averaged state. In order to correct too large easterly wind in an earlier model the interaction coefficients are specified as functions of latitude. The revised procedure is applied to a shallow water model in which addition of fluid is an analogue to the heating of the atmosphere. With a symmetric forcing the geopotential and the zonally averaged horizontal velocity should also be symmetric fields, while the stream function and the vorticity should be anti-symmetric. In the earlier calculations the zonally averaged winds were of too strong in the region close to the equator although the direction was determined in a correct way. The present calculations give an improved result with respect to the tropical easterlies. In the integrations it has been assumed that the meridional transport of vorticity may be described by interaction coefficients. This assumption makes it possible to determine in an indirect way the meridional momentum transport.