av weather exam 2

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What does vertical motion contribute to?

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185 Terms

1

What does vertical motion contribute to?

Atmospheric Stability (or instability) and can be the start of severe weather

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2

Since pressure always decreases with height, adiabatic cooling and heating will:

cooling will always accompany upward motion, heating will accompany downward motion

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3

What causes vertical motions to typically be much smaller than horizontal motions?

Hydrostatic Balance

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4

What weather radar should not be relied on?

Aircraft Radar

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5

What can cause small imbalances between the gravitational force and the Vertical Pressure Gradient?

Thunderstorms that cause large vertical accelerations and vertical motions

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6

what is it called when vertical motions are strong enough to affect aircraft motion?

VErtical gusts

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7

What are the most significant causes of vertical motion?

convergence/divergence, orography, fronts, convection

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8

What are embedded thunderstorms?

Thunderstorms obscured by massive cloud layers that cant be seen.

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9

Convergence:

Net horizontal inflow of air into an area

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10

When does convergence happen?

Wind speeds slow down in direction of flow or when opposing airstreams meet.

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11

Divergence

Net horizontal outflow of air in an area.

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12

When does Divergence happen?

Wind speeds increase in direction of flow or when airstreams spread out.

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13

What happens when surface winds converge?

Flowing in air is removed due to rising upward

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14

What happens when surface winds diverge?

Air sinks from aloft to replace air being removed at lower levels

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15

What happens aloft when surface winds diverge/converge?

You have both upwards and downwards motions, converging winds push out the air and diverging winds suck in the air

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16

Where does air tend to rise and sink?

rise in low pressure, sink in high pressure.

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17

Convergent winds tend to flow

into low pressure areas

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18

divergent winds tend to flow

out of high pressure areas

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19

Which ways do low and high pressure winds spiral?

low pressure are counter-clockwise, high pressure clockwise

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20
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21

When does friction cause surface winds to blow across isobars at a slight angle toward lower pressure?

in large scale flow (nearly geostrophic balance)

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22

Orographic lifting:

The lifting of an airmass when it encouters a hill or mountain

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23

What happens when wind hits mountains and peaks?

If the wind hits a mountain it goes up, when it crosses a peak it goes down.

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24

What does strength of vertical velocities depend on?

The speed of the wind blowing perpendicular to the mountain and the steepness of the terrain

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25

can orographic lifting cause storm activity?

yes but not usually. causes turbulence such as mountain lee waves

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26

front:

transition zone between two air masses of different densities

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27

airmass

an extensive body of air where the conditions of temperature and moisture are essentially uniform

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28

frontal lifting:

when a warm airmass lifts over a relative cold airmass, note that air can also descend over fronts

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29

convective lifting

occurs in unstable atmospheric conditions when a rising parcel of air is warmer than its surroundings

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30

what happens as warmer air wants to rise to become cooler?

the bubbles of warm air rise and the cooler air around the bubble sinks

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31

what vertical motion is cloud and storm formation associated with

convection/convective lifting

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32

mechanical turbulence

the turbulence produced when airflow is hindered by surface friction and/or obstruction

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33

what is the result of mechanical turbulence?

eddies: the surface friction slows the air in the lowest atmospheric layers, the air above still moves faster, this causes the air to roll up and cuases turbulence

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34

gravity waves

vertical oscillations of air parcels in a stable atmosphere

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35

how does gravity support equilibrium?

gravity plays are major role in return of displaced particles to their equilibrium level

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36

what doe speed, length, and direction of propagation depend on?

magnitude of initial displacement, atmospheric stability, wind

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37

what occurs under unstable atmospheric conditions and what occurs under stable atmospheric conditions

unstable: convection stable: gravity wave

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38

stable

when the airmass returns to its initial position after displacement

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39

unstable

airmass continues moving away after displacement

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40

neutral

airmass remains in new place after displacement

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41

atmospheric stability

a condition that makes it difficult for air parcels to move vertically

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42

atmospheric instability

a condition that promotes vertical motion of air parcels

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43

buoyancy

the property of an object that allows it to float on the surface of a liquid, or ascend through and remain freely suspended in a compressible fluid such as the atmosphere

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44

archimedes principle

when an object is placed in a fluid, it will be subjected to an upward or downward force depending on the weight of the the object and displaced fluid.

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45

dry adiabatic process

cooling of an unsaturated parcel of air by expansion and the warming of a parcel of air by compression

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46

dry adiabatic process temp change:

3 degrees C (5.4 farenheit) per 1000 feet

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47

adiabatic cooling:

cooling of gas by expansion, it is always associated with upward motion

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48

adiabatic heating

warming of gas by compression, always associated with downward motion

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49

why do air parcels cool when increasing in altitude?

because they expend energy while expanding to match the pressure of surrounding air

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50

unsaturated air flowing upslope cools at:

3 degrees C per 1000 feet

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51

why is ISA 2 degrees per 1000 feet?

isa doesnt account for vertical movement and air cooling by expansion

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52

sounding

measurement of meteorlogical conditions between the surface and some altitude

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53

lapse rate

decreased of temp rate with height

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54

how to evaluate stabilitiy?

dry adiabatic lapse rate = 3 degrees per 1000 ft when the LR is greater than DALR, atmosphere is absolutely unstable, when LR = DALR atmosphere is neutral, when LR<DALR the atmosphere is stable

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55

surface based inversion

an inversion with its base at ground level, often the result of surface cooling

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56

when the observed lapse rate is steep,

it approaches or exceeds the dry adiabatic lapse rate

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57

stable air is ________ than unstable air

smoother

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58

formation of stratiform or cumuliform clouds depends on

stability of air

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59

stable environment means vertical movements are

small and smooth

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60

unstable environments mean that vertical movements are

large and turbulent

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61

visibility in unstable condition is usually:

good

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62

surface based temp inversions occur on

clear cool nights with light or calm winds

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63

stability of airmasses are decreased by

heating from below

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64

unstable air is associated with

good visibility and rough low level flying especially in the afternoon and summer

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65

high pressure areas where the air is generally descending, atmosphere is most likely

stable

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66

low pressure areas where air is generally rising, atmosphere is most likely

unstable

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67

presence of fog, smoke, or haze indicates atmosphere is

stable

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68

what is an area of definite turbulence and wind shear?

elevated stable layer capping off an unstable area

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69

Which trace gas is the most important in weather formation?

water vapor

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70

water vapor:

colorless ordorless tasteless gas in which molecules are free to move about

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71

how is water vapor unique?

it can exist in 3 states in the atmosphere

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72

h2o transfering to higher energy states

melting (ice to water), evaporation (water to water vapor), sublimation (ice to water vapor)

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73

h2o transfering to lower energy states

condensation (water vapor to water). freezing (water to ice), and deposition (water vapor to ice)

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74

Change in molecular motion always is due to

temperature change

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75

latent heat

amount of heat absorbed or released during a change of state

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76

partial pressure

pressure exerted by any one of the gases that make up the mixture of gases in the atmosphere: all added together make the current pressure

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77

vapor pressure

partial pressure exerted by water vapor

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78

saturation

when the same amount of h2o is leave a water surface as returning

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79

saturation vapor pressure

partial pressure of water pressure at equilibirum

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80

what is saturation vapor pressure dependent on

temperature

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81

Relative humidity is relative to

saturation vapor pressure

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82

dew point:

temperature which air must be cooled to to become saturated

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83

what does dew point help anticipate?

precipitation, thunderstorms, icing

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84

dew

condensation that forms on an object when it loses heat energy through nocturnal radiation

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85

white dew

dew that has frozen

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86

frost

ice crystal deposition

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87

frostpoint

critical temp of frost

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88

cloud

a suspension of water droplet or ice crystals in the atmosphere

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89

3 requirements for a cloud

water vapor, condensation nuclei, cooling

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90

condensation nuclei

microscopic particles that serve as surfaces for water vapor to condense or depose on, examples are dust, salt, fog

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91

hygroscopic

having tendency to draw water from atmosphere

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92

cooling is usually the result of

contact of air with cold surface and adiabatic expansion

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93

contact cooling

process by which heat is conducted away from warmer air to colder surface, one way clouds are formed

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94

Contact cooling causes air stability to

increase

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95

advection fog

results from the transport of warm humid air over a cold surface

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96

radiation fog

occurs when radiation cooling of earth surface lowers air temp near ground to or below its initial dewpoint on calm clear nights.

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97

ground fog

radiation fog that is less than 20ft deep

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98

adiabatic cooling

cooling of gas by expansion

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99

if a cloud forms, the air likely was

moving upward

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100

if a cloud dissipates, the air likely was

moving down

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