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training forecasting (falah) > QG theory > Flashcards

QG theory Flashcards

1
Q
A
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2
Q

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

A
  • QG omega equation
  • QG geopotential tendency
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3
Q

geostrophic balance represents the

A

fundamental balance condition for mid-latitude synoptic-scale flow

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4
Q

The geostrophic wind approximation is only strictly valid in

A

regions of zero wind acceleration

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5
Q

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

A
  • 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)
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6
Q

Define ageostrophic wind

A

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.

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7
Q

Ageostrophic wind is defined mathematically as

A
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9
Q

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

A

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

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10
Q

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

A

divergence , wind field

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11
Q

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

A

presence of ageostrophic motion.

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12
Q

all vertical motion is due to the presence of

A

ageostrophic motion.

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13
Q

ageostrophic wind is entirely responsible for

A
  • the distribution of cyclones,
  • anticyclones,
  • clouds,
  • and precipitation in the atmosphere.
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14
Q

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 ……………………………….

A

often relatively small ageostrophic portion of the wind.

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15
Q

if the geostrophic wind is nondivergent, we have

A
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16
Q

the equation is for

A

relationship between ageostrophic wind and vertical motion

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17
Q

the equation means

A

divergece of ageostrophic wind in upper air causes upward motion

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18
Q

Equation for ageostrophic wind and horizontal acceleration:

A
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19
Q
A

Equation for ageostrophic wind and horizontal acceleration

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20
Q

Explain the following equation

A

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

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21
Q

Based on the equation we conclude three properties

A
  • 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.
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22
Q

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

A

continuity equation in isobaric coordinates.

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27
Q
A

Centripital acceleration

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28
Q
A

ageostrophic wind

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32
Q

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

A

the western side, upstream

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33
Q

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

A

downward vertical motion.

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34
Q

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

A

eastern , downstream

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35
Q

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

A

upward

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36
Q

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

A

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

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37
Q

obtain the geostrophic wind equations

A
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38
Q

based on the properties of the previous mathematical derivation, we see that the ageostrophic wind vector has three properties:

A
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39
Q

The following is an example of

A

Curvature in the wind field

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40
Q

The following is an example of

A

Speed change in the wind field

41
Q

Under such circumstances, the acceleration of the wind will be entirely a consequence of ………………………….

A

speed changes.

42
Q

A parcel of air located on the western edge of the entrance region would experience an acceleration in the……………………………

A

direction of the flow at that location

47
Q
A
48
Q

It can be shown that the rate of change of vorticity is strongly dominated by two processes

(change of vorticity with time)

A
  • Vorticity advection
  • Divergence
49
Q

vorticity advection is resembled by

A
50
Q

Divergence is resembled by

A
53
Q

Vorticity

A

Rotation of wind around vertical axis (cyclonic or anticyclonic) vertical or in a slope

54
Q

vorticity equation:

A
55
Q

what does the equation mean?

A

vorticity is changing due to vorticity advection and divergence

56
Q

storm has …………. vorticity

A

large

62
Q

the divergence term describe

A

the effects of divergence on the change of vorticity within a fluid.

63
Q

When divergence occurs in a fluid, vorticity becomes more …………………

A

anticyclonic

64
Q

When…………………… occurs in a fluid, vorticity becomes more anticyclonic

A

divergence

65
Q

When convergence occurs in a fluid, vorticity becomes more ……………..

A

cyclonic

66
Q

When ………………………..occurs in a fluid, vorticity becomes more cyclonic

A

convergence

67
Q

When divergence occurs in a fluid, vorticity becomes more anticyclonic. Thus, …………………………spins up …………………………..vorticity

A

convergence, cyclonic

68
Q

When ………………….occurs in a fluid, vorticity becomes more ……………………. Thus, convergence spins up cyclonic vorticity

A

divergence, anticyclonic

69
Q

Surface low-pressure centers are characterized by ………………………….and thus tend to be foci for the production of low-level cyclonic vorticity.

A

convergence

70
Q

Surface low-pressure centers are characterized by convergence and thus tend to be ……………………………………………………..

A

foci for the production of low-level cyclonic vorticity.

71
Q

upper divergence results in vorticity….

A

anticyclonic

72
Q

upper convergence results in……

A

cyclonic

73
Q

vorticity cyclonic (+ve or -ve)

A

+ve vorticity

74
Q

Term A

A

Vorticity minimum in the ridges

75
Q

Term B

A

Min. vorticity advection

76
Q

Term C

A

Maximum vorticity advection

77
Q

Term D

A

Vorticity max in the trough

78
Q

vorticity anticyclonic (+ve or -ve)

A

-ve vorticity

79
Q

Upstream of the trough, the geostrophic wind is directed from the ……………………………towards the ……………………………

A

vorticity minimum, vorticity maximum

80
Q

………………………………………., the geostrophic wind is directed from the vorticity minimum towards the vorticity maximum.

A

Upstream of the trough

81
Q

Downstream of the trough, the geostrophic wind is directed from the …………………………………. towards the ……………………………

A

vorticity maximum, vorticity minimum

82
Q

…………………………………………, the geostrophic wind is directed from the vorticity maximum towards the vorticity minimum.

A

Downstream of the trough,

83
Q

Note that regions of maximum vorticity advection is collocated with regions of …………………………………….

A

divergence

84
Q

Note that regions of …………………………………vorticity advection is collocated with regions of divergence

A

maximum

89
Q

The most important application of QG theory is

A

the diagnosis of vertical motion

90
Q

The fundamental equation of QG theory indicate that ………………….and ……………………………………are dynamically forced by two mechanisms:

–Vorticity advection
–Thermal advection

A

vertical motion 𝜔, geopotential height tendency 𝜒

91
Q

The fundamental equation of QG theory indicate that vertical motion 𝜔 and geopotential height tendency 𝜒 are dynamically forced by two mechanisms:

A
  • Vorticity advection
  • Thermal advection
92
Q

This parcel (the small circle) has some vorticity value as it enters the trough. Along its trajectory, it is encountering more and more

A

cyclonic vorticity values

93
Q

This parcel (the small circle) has some vorticity value as it enters the trough. Along its trajectory, it is encountering more and more cyclonic vorticity values. If it is to stay in equilibrium with its environment, it must

A

increase its vorticity

94
Q

This parcel (the small circle) has some vorticity value as it enters the trough. Along its trajectory, it is encountering more and more cyclonic vorticity values. If it is to stay in equilibrium with its environment, it must increase its vorticity through

A

horizontal convergence

95
Q

By this reasoning, parcels entering the backside of the trough, in a region of

A

anticyclonic vorticity advection (negative vorticity advection (NVA))have to converge

96
Q

By this reasoning, parcels entering the backside of the trough, in a region of anticyclonic vorticity advection (AVA) (that is, vorticity values are becoming more cyclonic along the flow) are having to converge. By the same argument, in the region of

A

cyclonic vorticity advection (CVA) on the other side of the trough axis, parcels are diverging.

97
Q

in this way, PVA implies

A

divergence

98
Q

NVA implies

A

convergence at any level in the atmosphere

99
Q
A
100
Q

generally speaking, PVA at 500 mb is

A

typically associated with PVA increasing with height

101
Q

NOT DONE

A

training forecasting (falah) (3 decks)

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