Instabilities Conducive to Aviation Turbulence

Abstract

Atmospheric instabilities, including static, Kelvin–Helmholtz (KHI), inertial, conditional, potential (convective), symmetric, conditional symmetric, and potential symmetric instabilities, might trigger aviation-scale turbulence such as the clear-air turbulence (CAT), mountain wave turbulence (MWT), and near-cloud turbulence (NCT) that are reviewed in this chapter. Energy conversion associated with several atmospheric instabilities is reviewed through an equation governing energy transfer in an inviscid, stably stratified shear flow, and the Taylor–Goldstein equation is used to prove a corollary of Howard’s semicircle theorem and the Miles–Howard Theorem. The criteria for static (gravitational) instability, conditional instability, potential instability, inertial instability, symmetric instability, conditional symmetric instability, and potential symmetric instability are discussed and summarized in a table. Their implications for the development of turbulence diagnostics or indices for aviation turbulence forecasting are also discussed.