# QG theory Flashcards

governing equations describe

the behavior of the atmosphere

cons if governing equations

they are complex and thus it’s difficult to conceptualize the dynamical essence of synoptic-scale weather systems using the full set of equations.

How was the governing equations simplified?

- by utilizing the observation that the flow in synoptic-scale weather systems is approximately geostrophic.
- By using a carefully designed set of assumptions

Define the quasigeostrophic theory

simplified the governing equations of motion and combined them in ways that retain the fundamental dynamics of weather systems and yet are simple enough to comprehend.

The QG framework simplifies the equation of motions into a set of **diagnostic equations**

- QG omega equation
- QG geopotential tendency

geostrophic balance represents the

fundamental balance condition for mid-latitude synoptic-scale flow

The geostrophic wind approximation is only strictly valid in

regions of zero wind acceleration

There are two broad categories of flow in the atmosphere that will violate geostrophic balances

- Wind speed changes along the flow (i.e. jet streaks, regions of speed convergence/divergence)
- Wind direction changes along the flow (i.e. troughs and ridges, regions of confluence/diffluence)

Define **ageostrophic** **wind**

The degree of departure from geostrophic balance that characterizes synoptic-scale motions can be assessed by considering the difference between the actual wind at a location and the calculate geostrophic wind at the same point.

Ageostrophic wind is defined mathematically as

………………………, this implies that the geostrophic wind is non-divergent.

Because all divergence/convergence necessarily implies an acceleration of the wind field,

ALL…………………… in the synoptic-scale………………………………. is due to the presence of ageostrophic motion.

divergence , wind field

ALL divergence in the synoptic-scale wind field is due to the

presence of ageostrophic motion.

all vertical motion is due to the presence of

ageostrophic motion.

ageostrophic wind is entirely responsible for

- the distribution of cyclones,
- anticyclones,
- clouds,
- and precipitation in the atmosphere.