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Flashcards in QG theory Deck (31):
1

governing equations describe

the behavior of the atmosphere

2

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.

3

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

4

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.

5

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

  • QG omega equation
  • QG geopotential tendency

6

geostrophic balance represents the

fundamental balance condition for mid-latitude synoptic-scale flow

7

The geostrophic wind approximation is only strictly valid in

regions of zero wind acceleration

8

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)

9

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.

10

Ageostrophic wind is defined mathematically as

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11

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

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

12

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

divergence , wind field

13

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

presence of ageostrophic motion.

14

all vertical motion is due to the presence of

ageostrophic motion.

15

ageostrophic wind is entirely responsible for

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

16

Despite the fact that the mid-latitude atmosphere is predominately in geostrophic balance, all of the important weather with which we are confronted develops as a direct result of the .....................................

often relatively small ageostrophic portion of the wind.

17

To derive the relationship between ageostrophic wind and vertical motion, we first will write the

continuity equation in isobaric coordinates.

18

if the geostrophic wind is nondivergent, we have

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19

the equation is for

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relationship between ageostrophic wind and vertical motion

20

the equation means

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divergece of ageostrophic wind in upper air causes upward motion 

21

Equation for ageostrophic wind and horizontal acceleration:

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22

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Equation for ageostrophic wind and horizontal acceleration

23

Explain the following equation

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Vag = Acceleration term in momentum equation and​ 1/f

24

Based on the equation we conclude three properties 

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  • The ageostrophic wind is a measure of the horizontal acceleration in the atmosphere
  • The ageostrophic wind is perpendicular to the horizontal acceleration vector
  • The ageostrophic wind is directed to the left of the acceleration vector in the Northern Hemisphere.

25

The ageostrophic winds converge on ............................of the upper trough (on its ..................side)

the western side, upstream

26

The ageostrophic winds converge on the western side of the upper trough (on its upstream side), leading to ....................

downward vertical motion.

27

The ageostrophic winds divergence on the .....................side of the upper trough (on its ..............................side), 

eastern , downstream

28

The ageostrophic winds divergence on the eastern side of the upper trough (on its downstream side), leading to .......................vertical motion.

upward

29


........................................... explains why there tends to be cloudy/stormy weather downstream of an upper level trough

divergence on the eastern side of the upper trough (on its downstream side), leading to upward vertical motion.

30

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Centripital acceleration

31

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ageostrophic wind