16 articles
Ageostrophic wind
The ageostrophic wind is the component of the actual wind left after subtracting the geostrophic wind, the balanced flow, and it produces divergence and vertical motion.
Available potential energy
Available potential energy (APE) is the portion of the atmosphere's potential energy convertible into kinetic energy, formally defined by Edward Lorenz at MIT in 1955.
Baroclinic instability
Baroclinic instability is a fluid-dynamical instability of rotating, stratified flow that converts available potential energy from a horizontal temperature gradient into kinetic energy, and it is the primary cause of synoptic-scale midlatitude storms.
Barotropic instability
Barotropic instability is a fluid-dynamical instability of horizontally sheared flow in which disturbances draw kinetic energy directly from the background shear, contrasting with baroclinic instability.
Brewer–Dobson circulation
The Brewer–Dobson circulation (BDC) is the stratosphere's global overturning circulation: air rises in the tropics, moves poleward, and descends in middle and high latitudes of each hemisphere, controlling ozone transport.
Eady model
The Eady model is an idealized analytical model of baroclinic instability, introduced by Eric Eady in 1949, which with Charney's 1947 model founded the study of extratropical circulation.
Ferrel cell
The Ferrel cell is the mid-latitude overturning circulation of the atmosphere, sitting between the Hadley and polar cells and producing the prevailing westerlies, first proposed by William Ferrel in 1856.
Geostrophic flow
Geostrophic flow is air or water motion in which the pressure-gradient force and Coriolis force balance, so flow moves parallel to isobars rather than across them.
Gradient wind
The gradient wind is a horizontal wind blowing parallel to curved isobars, balancing the pressure gradient, Coriolis, and centrifugal forces; it generalizes the geostrophic wind to curved flow.
Omega equation
The omega equation is a diagnostic equation of quasi-geostrophic theory that determines vertical velocity in synoptic-scale atmospheric flow from geostrophic wind, pressure, and temperature fields, without time derivatives.
Polar cell
The polar cell is the smallest and weakest of the three atmospheric circulation cells in each hemisphere, where air rises near 60–70° latitude and sinks over the pole.
Potential vorticity
Potential vorticity (PV) is a quantity in atmospheric and oceanic fluid dynamics combining a parcel's absolute vorticity with its stratification; conserved in adiabatic, frictionless flow, it underlies the dynamic tropopause.
Primitive equations
The primitive equations are the set of atmospheric and oceanic motion equations, simplified by the hydrostatic approximation, used in most numerical weather prediction and climate models.
Quasi-geostrophic theory
Quasi-geostrophic (QG) theory is a simplified system of equations for large-scale midlatitude atmospheric and oceanic flow, developed mainly by J. G. Charney in the late 1940s and still central to weather forecasting.
Thermal wind
The thermal wind is the vertical shear of the geostrophic wind, a key relation in atmospheric dynamics showing how horizontal temperature gradients control wind change with height.
Vorticity equation
The vorticity equation is the evolution equation for vorticity, the curl of a fluid's velocity, governing rotation changes through stretching, tilting, baroclinic generation, and diffusion.