The Behavior of Winter Stationary Planetary Waves Forced by Topography and Diabatic Heating

Abstract

A primitive equation linear wave model is developed to examine the effects of mean zonal wind structure on the vertical propagation of stationary planetary waves and to identify the characteristics of the winter stationary waves forced by realistic topography and diabatic heating. An analytic mean zonal wind model is used to facilitate changing the wind structure parameters for comparative experiments. A more realistic mean wind profile is used to simulate the observed behavior of stationary waves more closely. The experiments confirm the sensitivity of vertical wave propagation to the mean wind structure, especially to the latitudinal curvature of the mean wind. The role of the polar night jet in channeling the planetary waves as they propagate vertically is emphasized. At is found that the latitudinal location of the polar night jet also has a significant influence upon the wave propagation. A mechanism is proposed to explain the possible connections between the change in the location of the polar night jet and stratospheric sudden warmings during winter. The model with topographic forcing reproduces quite realistic wave patterns both in the troposphere and stratosphere, whereas the model with diabatic heating does not have this ability, indicating that topographic forcing plays a more important role than diabatic heating for maintaining the stationary waves during winter, especially in the stratosphere.