I got about 3 pages into this and felt like I was following the discussion until the discussion of an incorrect prediction result that:<p>&gt; In fact, the spurious tendencies are due to an imbalance between the pressure and wind fields resulting in large amplitude high frequency gravity wave oscillations.<p>Since this paper was published within the last 20 years, I can&#x27;t imagine what they were referring to by &#x27;gravity waves&#x27;<p>Do you know what is meant by this statement?