CONVECTIVE GENERATION OF GRAVITY-WAVES IN VENUSS ATMOSPHERE - GRAVITY-WAVE SPECTRUM AND MOMENTUM TRANSPORT

The emission of internal gravity waves from a layer of dry convection embedded within a stable atmosphere with static stability and zonal wi nds varying in height is calculated. This theory is applied to Venus t o investigate whether these waves can help support the westward maximu m of angular momentum of Venus's middle atmosphere. The emission mecha nism is similar to that suggested for driving the gravity modes of the Sun and relates the amplitude and spectrum of the waves to the amplit ude and spectrum of the convection. Waves are damped by several mechan isms: wavebreaking in the stable atmosphere, critical layer absorption , reabsorption by the convection, and wave radiation to space. The aut hors use plane parallel geometry without rotation and assume sinusoida l wave fluctuations in the horizontal dimensions. The vertical depende nce is determined using the WKBJ approximation. It is found that conve ctively generated gravity waves do not exert an acceleration where the westward winds are greatest. Instead, they deposit westward momentum in a I-km thick layer just above the convection. Other waves deposit e astward momentum far above the westward wind maximum where deceleratio ns can exceed 20 ms(-1) day(-1), comparable to deceleration amplitudes in Earth's mesosphere. Although the momentum fluxes by gravity waves are substantial, the vertical profile of acceleration does not match w hat is required for supporting Venus's atmospheric superrotation.