What is the quasi-geostrophic theory?
The basic idea of quasi-geostrophic theory (and other quasi- balanced theories) is that the potential vorticity is inverted to obtain the geostrophic velocity and the associated mass field. Quasi-geostrophy advects potential vorticity and other quantities with the geostrophic rather than the total wind.
Is increasing with height will lead to height falls while caa increasing with height will lead to height rises?
CAA is increasing with height (decreasing with pressure) and WAA is decreasing with height (increasing with pressure). This causes , so , so (height rises). height causes height falls (rises).
What is Geostrophic approximation?
The Geostrophic Approximation on Constant Height Surfaces The geostrophic relationship gives the approximate relationship between the horizontal pressure gradient and the horizontal velocity (as scaled by the Coriolis parameter) in large-scale extratropical/mid-latitude weather systems.
What is the source of vertical motion in a QG atmosphere?
According to QG Theory, both differential horizontal warm air advection and vertical differential positive vorticity advection contribute to upward vertical motion.
What is ageostrophic wind?
A wind above the boundary layer that blows at a different speed from that of the geostrophic wind predicted by the pressure-gradient force.
Does geostrophic wind have zero divergence?
You already showed in Lab 1 that the divergence of the geostrophic wind is zero (this is not really true, but the reasoning for that awaits future lectures). Thus the horizontal divergence is really due to the divergence of the ageostrophic wind. If there is no ageostrophic wind, therefore, there can be no divergence.
Why do wind follow isobars?
Wind derives its initial speed and direction from changes in air pressure over distance, or pressure gradient force (PGF). This is why when isobars are packed closer together (larger pressure gradient), wind speeds tend to increase. This makes winds cross isobars, toward lower pressure.
What are the effect of winds basing on the geostrophic?
Winds near the surface: Winds affected by friction. Geostrophic wind blows parallel to the isobars because the Coriolis force and pressure gradient force are in balance.
What is cold or warm air advection?
Very simply, advection occurs any time an airmass moves. When a warm airmass moves into an area previously occupied by a cooler airmass, Warm Air Advection (WAA) occurs. Cold air replacing warm air is known as Cold Air Advection (CAA). Each of these processes unfolds differently, and produces different results.
Where is Ageostrophic wind strongest?
We can immediately see that the ageostrophic wind has the greatest magnitude in the base of the trough, where the jet is strong and curvature is strongest. We can also notice that the vectors point upstream within the cyclonically curved area and downstream within the anticyclonically curved areas.
What is Supergeostrophic flow?
A gradient flow through a ridge is termed “supergeostrophic”. The “super” means the wind speed is greater than what would be expected if the wind was geostrophic.
What happens when the isobars are close together?
The lines around high and low pressure on a weather map are called isobars, or lines of equal pressure, as shown in the above image on the left. When isobars are close together it is very windy; when they are further apart, conditions are more calm. The wind around highs always blows in a clockwise direction.
What is a quasi geostrophic equation?
Quasi-geostrophic equations. While geostrophic motion refers to the wind that would result from an exact balance between the Coriolis force and horizontal pressure-gradient forces, quasi-geostrophic (QG) motion refers to flows where the Coriolis force and pressure gradient forces are almost in balance, but with inertia also having an effect.
What causes quasi-geostrophic temperature change?
Equation 10 states that quasi-geostrophic temperature change at a particular location and height is a function of temperature advection and vertical motion. Warm (cold) advection causes a temperature increase (decrease). Ascent ( ) causes adiabatic cooling and a temperature decrease ( ), while descent ( ) produces adiabatic heating.
What is the difference between geostrophic and quasi-geostrophic motion?
While geostrophic motion refers to the wind that would result from an exact balance between the Coriolis force and horizontal pressure-gradient forces, quasi-geostrophic (QG) motion refers to flows where the Coriolis force and pressure gradient forces are almost in balance, but with inertia also having an effect.
What are the terms in the quasi-geostrophic omega equation?
The BASIC Quasi-geostrophic Omega Equation: Term A Term B Term C Term C: Horizontal Temperature Advection • These height changes where not a result of changes in geostrophic vorticity • Thus, in order to maintain geostrophic balance in the absence of vorticity advection, local height rises must be accompanied