Transmission of three-dimensional anelastic internal gravity wave packets across retrograde jets

The transmission of three-dimensional anelastic internal gravity wave packets incident upon a retrograde background jet flow are examined through fully nonlinear numerical simulations. The background winds are chosen to be representative of the eastward and westward flows of the Quasi-Biennial Oscillation (QBO) in the equatorial stratosphere. Transmission, which is quantified by the relative pseudomomentum of waves passing above the jet, is found to be smaller for incident waves with larger initial frequency. Due to anelastic effects, the amplitude of the transmitted wave packets tends to grow exponentially, ultimately inducing a local mean flow that acts to drive the waves to overturn and break turbulently. The results are compared with previous studies that predicted transmission of small amplitude wave packets, and implications are discussed for the influence of wave transmission across the QBO.