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Synoptic Meteorology-II > Chapter-4: Fronts and Jets > Flashcards

Chapter-4: Fronts and Jets Flashcards

1
Q

Define Synoptic

A

seen at the same time/together “simultaneous observations”

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2
Q

Midlatitude is also known as

A

Extra-tropics

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3
Q

Define midlatitude

A

between 23o27’ N and 66o33’N and between 23o27’ S and 66o33’ S latitude, or, the earth’s temperate zones between the tropics and the arctic and antarctic polar regions

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4
Q

important weather in the midlatitude

A

fronts and extratropical cyclones

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5
Q

front is defined as

A

a transition zone between two air masses of different temperatures/densities.

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6
Q

These atmospheric fronts are

A

hree-dimensional zones

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7
Q

These atmospheric fronts are three-dimensional zones that represent:

A
  • a rapid transition of the thermal field
  • marked shift in the wind direction
  • a significant transition in the moisture field
  • an increase in the magnitude of the wind
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8
Q

The thermal gradient is usually largest at ………………………………..and weakens as the …………………………….

A

the Earth’s surface

zone slopes upward

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9
Q

The transition zone may extend over a distance of………………………………….., and a typical ……………………………………..ratio is ……………….

A

1000 km or more along the Earth’s surface

cross-front to along-front

1:10

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10
Q

a front is:
​…………………… and …………………… (………km)

A

long and wide (100 km)

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11
Q

frontal zones:

A

Polar front

Arctic front

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12
Q

mP stands for:

A

Maritime polar

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13
Q

mT stands for:

A

Maritime tropical
warm, moist

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14
Q

cT stands for:

A

Continental tropical
hot, dry

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15
Q

cA stands for:

A

Continental arctic
very cold, dry

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16
Q

cP stands for:

A

Continental Polar
cold, dry

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17
Q

The polar front boundary:

A

eparates warm, humid air to the south from cold polar air to the north, extends upward to over 5 km.

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18
Q

arctic front:

A

separates cold air from extremely cold arctic air, is much more shallow than the polar front and only extends upward to an altitude of about one or two kilometers.

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19
Q

Fronts are observed at ………………….in ……………………………………….and are associated with………………………………………………..

A

all longitudes

the extratropical latitude belt

most of the significant weather events.

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20
Q

A jet is

A

an intense, narrow, quasihorizontal or horizontal current of wind that is associated with strong vertical shear.

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21
Q

Atmospheric jet streams dimention

A

thousands of kilometers long, a few hundred kilometers wide, and only a few kilometers thick.

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22
Q

Wind speeds in the central core of a jet stream often

A

exceed 100 knots and occasionally exceed 200 knots.

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23
Q

Jet streams are usually found at the ……………………………at elevations between ………………………….., although they may occur at …………………………………….

A

tropopause

10 and 15 km

both higher and lower altitudes.

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24
Q

subtropical jet stream

A

the jet stream situated near 30° latitude at about 13 km above the subtropical high

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25
Q

polar front jet stream is also known as

A

polar jet stream

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26
Q

polar front jet stream

A

jet stream situated at about 10 km (33,000 ft) near the polar front

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27
Q

Both fronts and jets are usually marked by

A

a concentration of isotherms (strong temperature gradient) and strong vertical wind shear

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28
Q

Fronts and jets are …………………..phenomenon because………………………………………….

A

hybrid

each is characterized by two different horizontal scales that differ by as much as an order of magnitude.

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29
Q

If the length of a front or jet is on the order of …………………….., then the Rossby number is usually reasonably small for flow along the front or jet so that ……………………………………………

A

1000 km

geostrophic balance is approximately maintained across but not along the front or jet.

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30
Q

…………………………………………………………………are associated with jets and jet streaks through the ………………………………………, and hence a dynamical explanation of fronts also explains jets.

A

Long, narrow zones of strong temperature gradient

thermal wind relation

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31
Q

Long, narrow zones of strong temperature gradient are associated with jets and jet streaks through the thermal wind relation, and hence a dynamical explanation of fronts also explains jets.

This, of course, may not be true for

A

smaller scale fronts and jets

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32
Q

a theory that explains fronts may also explain jets. ……………………. and………………………are often discussed together as……………………………….

A

Upper-level fronts and jets

jet-front systems

33
Q

Types of Fronts

A
  1. cold front
  2. warm front
  3. Quasi-stationery front
34
Q

A front is classified based on

A

the movement relative to the warm and cold air masses

35
Q

Cold Front

A
  • A cold front is one that moves in a direction in which cold air displaces warm air at the surface.
  • In other words the cold (or cooler) air mass is moving toward a warmer air mass.
  • The cooler, denser air is sliding under the warmer, less dense air displacing it upward.
36
Q

Draw “cold front”

A
37
Q

Warm Front

A
  • A warm front is one along which warmer air replaces colder air.
  • In this case, a warmer air mass is moving toward a cooler retreating air mass.
  • The warmer, less dense air moves only toward and replaces the colder, denser air if the colder air mass is also moving.
38
Q

Draw “warm front”

A
39
Q

Quasi-Stationery Front

A
  • This type front is one along which no one air mass appreciably replace the other.
  • These fronts are stationary or nearly so (speed under 5 knots). They can move or undulate toward either the cold or warm air mass.
  • If the air masses on both sides of the boundary line are moving parallel to each other, the front will not move.
40
Q

Draw “Quasi-Stationery Front”

A
41
Q

Occluded Front

A

one where a cold front overtakes a warm front, forcing the warm air upward.

42
Q

The occluded front may be

A

either a warm front or a cold front type

43
Q

warm front type

A

one in which the colder air behind the cold front overrides the cold air in advance of the warm front, resulting in a cold front aloft.

44
Q

Cold front type

A

one in which the cold air behind the cold front under rides the warm front, resulting in a warm front aloft.

45
Q

Draw “occluded front”

A
46
Q

To describe the frontal general characteristics, we consider

A

the horizontal and vertical distribution of three weather elements (temperature, wind, and pressure) in a frontal zone.

47
Q

Typical fronts always consist of

A

warm air above cold air

48
Q

The frontal zone slope ………………………………………………………………………………..

A

upwards over colder air mass as a relatively narrow layer where the normal decrease of temperature with height, is reversed (temperature inversion).

49
Q

The frontal zone slope upwards over colder air mass as a relatively narrow layer where the normal decrease of temperature with height, is reversed (temperature inversion).

This temperature inversion is called

A

frontal inversion

50
Q

A cold front generally shows a ………………………………… than a …………………………..

A

stronger inversion

warm front.

51
Q

Draw a graph of the frontal characteristics

A
52
Q

Frontal characteristics

A
  1. temperature
  2. winds
  3. veering
  4. backing
  5. pressure
53
Q

describe frontal characteristic “wind”

A

A front is associated with wind shifts in a cyclonic direction (veering) at the surface. This is true with the passage of all frontal types.

54
Q

The wind direction also shifts in the vertical with ………………….in two ways:

A

height

Veering and backing

55
Q

Veering:

A
  • Veering is a change in wind direction, clockwise in the Northern Hemisphere. Ex: wind changes from southwest to northwest.
  • Veering generally occurs through a warm front.
56
Q

Backing

A
  • If the wind direction changes in anticlockwise direction, it is called backing. Ex: wind changes from northwest to southwest.
  • Backing occurs with height through a cold front.
57
Q

One of the important characteristics of all fronts is that (pressure)

A

on both sides of a front the pressure is higher than at the front.

58
Q

Fronts are associated with

A

troughs of low pressure

59
Q

A trough is

A

an elongated area of relatively low pressure. A trough may have U-shaped or V-shaped isobars.

60
Q

Friction causes the wind near the ground to

A

drift across the isobars toward lower pressure.

61
Q

Friction causes the wind near the ground to drift across the isobars toward lower pressure.

This causes a

A

cross-isobaric flow towards the front from both sides, resulting in convergence and rising motion in the region of a front.

62
Q

This causes a cross-isobaric flow towards the front from both sides, resulting in convergence and rising motion in the region of a front.

This is an important characteristic of fronts, since

A

the lifting of the air causes condensation, clouds, and weather.

63
Q

Draw Vg after friction force

A
64
Q

Draw wind veering at the surface of a cold and warm front

A
65
Q

Another important characteristic of fronts is their

A

slope

66
Q

Another important characteristic of fronts is their slope, with which the ………………………………………….. are associated

A

weather, intensity of weather and the movement of fronts

67
Q

The slope is the

A

ratio of the vertical rise to horizontal distance

68
Q

A slope of 1:50 (1 mile vertically for every 50 miles horizontally) would be
considered a

A

steep slope

69
Q

and a slope of 1:300 a

A

gradual slope

70
Q

Factors favoring a steep slope are:

A
  • a large wind velocity difference between air masses
  • large temperature difference and
  • high latitude
71
Q

Because cold air tends to run under warm air, the steeper the slope, the

A

more intense the lifting and vertical motion of the warm air and, therefore
the more intense the weather

72
Q

Across the frontal zone, there is a

A

stronger horizontal temperature gradient

73
Q

Across the frontal zone, there is a stronger horizontal temperature
gradient, which is strongest near

A

the surface, and weakens with increasing altitude

74
Q

According to the thermal-wind relationship

A

the geostrophic wind will increase with height in strong horizontal temperature gradients.

75
Q

If the frontal zone extends vertically over a large portion of the troposphere, then the wind speed

A

will continue to increase with height, reaching a maximum near the tropopause

76
Q

jet streams are associated with

A

frontal zones.

77
Q

The jet blows parallel to the

A

frontal zone

78
Q

The jet blows parallel to the frontal zone, with greatest wind speeds on

A

the warm side of the frontal zone

79
Q
A

Synoptic Meteorology-II (7 decks)

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