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Intro to met > Chapter 5: Wind > Flashcards

Chapter 5: Wind Flashcards

1
Q

wind is

A

a horizontal movement of air

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2
Q

Differences in temperature create

A

differences in pressure

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3
Q

Wind is a horizontal movement of air. Differences in temperature
create differences in pressure. The pressure differences drive

A

a complex system of wind in a never ending attempt to reach equilibrium

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4
Q

Wind is a horizontal movement of air. Differences in temperature create differences in pressure. The pressure differences drive a complex system of wind in a never ending attempt to reach equilibrium. So the wind is the result of

A

horizontal differences in air pressure

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5
Q

The wind direction is measured by

A

the wind vane

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6
Q

The wind direction is measured by the wind vane. This instrument,
which is a common sight on

A

many buildings, always points into the wind

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7
Q

The wind direction is measured by the wind vane. This instrument,
which is a common sight on many buildings, always points into the wind,
sometimes the wind direction is shown on

A

a dial that is connected to the wind vane.

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8
Q

The dial indicates

A

the direction of the wind either by points of the compass-that is, North (N), Northeast (NE), East (E), southeast (SE), and so on or by a scale of 0 to 360

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9
Q

On latter scale.0 (or 360) is

A

north. 90 is east, 180 is south and 270 is west

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10
Q

If the wind blows from the west the wind direction is

A

westerly

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11
Q

If the wind blows from the west the wind direction is westerly, if it from the south east – its

A

south easterly and so on

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12
Q

The wind speed units are:

A

meter per second m/s
kilometer per hour km/hour
knot; one knot = 0.51 m/s or = 1.9 km/hour.

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13
Q

Factors affecting wind:

A

Force generating wind (pressure gradient force)

Coriolis force

Friction

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14
Q

Pressure differences must create

A

a force in order to drive the wind this force is pressure gradient force.

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15
Q

Pressure differences must create a force in order to drive the wind this force is pressure gradient force. The force is from

A

higher pressure to lower pressure and is perpendicular to the isobars or contours.

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16
Q

The larger pressure differences ( ……………………….) the……………………. the …………………….

A

( the closer the spacing between the isobars) the stronger the pressure gradient force, the stronger is the Wind.

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17
Q

The magnitude of the pressure gradient force is a function of

A

the pressure difference between two points and air density

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18
Q

PGF
It can be expressed as:

A

-(1/p)(Δp/Δx)

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19
Q

All free moving objects including wind are deflected to

A

the right of their path of motion in the Northern Hemisphere and to the left in the Southern Hemisphere.

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20
Q

All free moving objects including wind are deflected to the right of
their path of motion in the Northern Hemisphere and to the left in the
Southern Hemisphere.
The reason of this deflection is

A

the earth’s rotation

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21
Q

For example if a rocket moved from the North Pole toward a target on the
Equator and took one hour to arrive its target, then the earth will rotate

A

15o in this time

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22
Q

For example if a rocket moved from the North Pole toward a target on the
Equator and took one hour to arrive its target, then the earth will rotate 15 in this time. So the rocket would look as it

A

veers off its path and hit the ground 15o west of the target

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23
Q

Coriolis force

A

deflects the free moving objects to the right in the Northern Hemisphere because of its counter clockwise rotation, and to the left in the southern Hemisphere because of the clockwise rotation of the earth in the Southern Hemisphere

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24
Q

The mathematical formula of computing the Coriolis force is :

A

Fc= 2ων sinθ

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25
Q

Where Fc is

A

the Coriolis force measured in m/s2

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26
Q

ω Is

A

the angular rotation of the earth (which is equal 7.29x10-5 rad/s

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27
Q

The main properties of the Coriolis force are:

A
  • Fc is directly proportional the latitude and wind speed.
  • It deflects the free-moving object to the right in the N.H. and to the left in the S.H.
  • It affects the wind direction only not affects the wind speed.
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28
Q

Friction

A

acts to slow a moving objects and to change the direction. Its direction is always opposite to the direction of the wind.

29
Q

Friction as a factor affecting wind is important only within

A

the first few kilometers of the atmosphere

30
Q

The roughness of the of the terrain determines

A

the angle at which the air flow will cross the isobar as will as influencing the speed at which it will move

31
Q

Where the friction is low (over smooth ocean surface), air moves at an angle of

A

10 to 20 degrees with the isobar and at speeds roughly two-third of the geostroghic wind.

32
Q

The geostroghic wind is

A

the resultant wind of the balance between the pressure gradient force and the Coriolis force on the free atmosphere.

33
Q

On the free atmosphere the effect of the friction force is

A

negligible.

34
Q

Over the rigged terrain the angle between the wind direction and the isobar is

A

high (may reach 30-45 degrees) and the wind speed is reduced by much as 50 % of the geostroghic wind.

35
Q

As said earlier, friction significantly influences

A

airflow near the earths surface and negligible at a height of few kilometers above

36
Q

Aloft where is no friction the Coriolis force

A

balances the pressure gradient force and deflects the wind direction to the right at an angle of 90 in the Northern Hemisphere to move in a direction parallel to the contours

37
Q

Contours are

A

the lines of equal heights. This wind is called geostroghic wind

38
Q

gradient wind:

A

this is assumption to calculate wind in uniform circular systems such as tropical cyclones.

39
Q

object moving around a circle needs

A

a force that is overcoming the desire of the object to move at a straight line. the force is called centripital force.

40
Q

define gradient wind

A

the wind which is a result of the balance of forces that are forcing the air to move in a uniform circle. those two forces are pressure gradient and corriolis

41
Q

thermal wind is

A

the change in the amplitude or sign of the geostrophic wind due to a horizontal temperature gradient. it is the difference between the upper and lower geostrophic wind.

42
Q

thermal wind is used to indicate

A

the thermal advection in a baroclinic atmosphere

43
Q

thermal wind is parallel to

A

the thickness

44
Q

the cold air (lower thickness) is to ………………………..

A

the left of the thermal wind

45
Q

cold advection:

A

thermal wind causes the geostrophic wind to rotate counterclockwise with heigh (backing)

46
Q

warm advection

A

thermal wind causes the geostrophic wind to rotate clockwise with heigh (veering)

47
Q

ageostrophic wind

A

the difference between actual and geostrophic winds

48
Q

ageostrophic wind is used to

A

include the effect of divergence in the upper air

49
Q

ageostrophic wind is measured by

A

soundings (radiosondes) and geostrophoc

50
Q

the ageostrophic wind is the value that is causing

A

the vertical motion

51
Q

despite the fact that the midlatitude atmosphere is predominantly in

A

geostrophic balance

52
Q

despite the fact that the midlatitude atmosphere is predominantly in geostrophic balance, all weatehr occuring there is a result of

A

this small porion of wind(the ageostrophic) so it is responsible for the distribution of cyclones, anticyclonic, clouds and precipitation in the atmosphere

53
Q

the ageostrophic wind is used to measure the horizontal acceleration in the

A

curvature and jets. it is normal to them and directed to the left.

54
Q

Jet streams:

A

Wind in the average increases with height throughout the troposphere cumulating in a maximum near the level of the tropopause.

55
Q

Jet streams:
Wind in the average increases with height throughout the troposphere
cumulating in a maximum near the level of the tropopause. This maximum
winds tend to be

A

further concentrated in a narrow bands

56
Q

Jet streams:
Wind in the average increases with height throughout the troposphere
cumulating in a maximum near the level of the tropopause. This maximum
winds tend to be further concentrated in a narrow bands. These narrow bands
of strong winds meandering through the atmosphere at a

A

level near the tropopause

57
Q

Types of jet streams

A

polar jet stream which is concentrated in midlatitude between 40o and 60o.
- subtropical jet stream at 30o latitude.

58
Q

Main characteristics of the jet streams:

A
  • jet streams typically occur in the break of the tropopause.
    • the form in area of intensified temperature gradients.
    • the wind speed must be 50 knots or greater to cla ssify as a jet stream.
    • the jet stream maximum is not constant rather its broken into segments.
    • the polar jet shifts farther south and it is stronger in winter than in summer.
    • jet stream segments move with the pressure ridges and troughs in the upper atmosphere.
59
Q

Local terrain features such as mountains and shore lines influence

A

local winds and weather.

60
Q

Mountain and Valley wind:

A

In the daytime air next to a mountain slope is heated by the contact with the ground as it receives radiation from the sun. The air usually becomes than air at the same altitude but farther from the slope. Colder denser air in the surroundings settles downward and forces the warmer air near the ground up the slope. This wind is a Valley wind, so called because the air is flowing up out of the valley.

At night the air in contact with the mountain slope is cooled by terrestrial radiation and becomes heavier than the surrounding air. It sinks on the slope producing the Mountain wind which flows l ike water down the mountain slope Mountain winds are usually stronger than valley winds, especially in winter.

61
Q

Land and Sea breezes:

A

As we know land surfaces warm and cool more rapidly than do water
surfaces, therefore land is warmer than the sea during the day. So wind
blows from cool water to warm land.

62
Q

The sea breeze so called because

A

it blows from the sea. At night the wind reverses, blows from cool land to warmer and creates the “land breeze”. Land and sea breeze develop only when the overall pressure gradient is weak.
Wind with stronger pressure gradient mixes the air so rapidly that local temperature and pressure gradient do not develop along the shore line.

63
Q

the speed units

A

knot, meter per second, kilometer per hour and feet per second which they are related by: 1 kt= 0.515 m/s = 1.853 km/h =1.152 mi/h = 1.689ft/s

64
Q

wind speed may be indicated in

A

makes use of familiar, natural phenomena connected with different wind speeds.

65
Q

An anemometer is a device for measuring

A

wind speed and direction

66
Q

An anemometer is a device for measuring wind speed and direction. The term is derived from the Greek word anemos, meaning

A

wind

67
Q

An anemometer is a device for measuring wind speed and direction. The term is derived from the Greek word anemos, meaning wind. It is divided into:

A

Wind Vane. Wind vane measures the wind direction.
- A cup anemometer. The cup anemometer measures the wind speed. The wind speed is read from a dial much like the speedometer of an automobile.

68
Q

Wind sock consists of

A

a cone shaped bag that is open at both ends. The degree to which the sock is inflated is an indication of the strength of the wind.

Intro to met (10 decks)

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