On the Structure and Behavior of Transient Waves during January 1979

Abstract

A numerical calculation of the atmospheric 16-day wave mode under a realistic zonal mean wind distribution and a linearr model simulation of transient waves during January 1979 were performed. The results were compared with the analysis of the FGGEIIIb data set for the same period.
It was found that the 16-day wave mode solution using a zonal mean field during January exhibits barotropic features of the normal mode in the troposphere and lower stratosphere. In the upper atmosphere, it bears more resemblance to a forced baroclinic wave mode due to the significant influences of the zonal mean wind and damping.
The linear model simulation was performed by using the time-dependent wavenumber 1 component of the geopotential height at the 500mb level of the FGGEIIIb data set as the lower boundary condition. The behavior of the transient wave was found to be similar to that of the 16-day wave mode solution.
The results of the numerical simulation and the structure of the 16-day wave mode solution are in good agreement with the analysis of the FGGEIIIb data set. This implies that the transient waves of January 1979 were dominated by the atmospheric 16-day wave mode.