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ASTC > Snow A > Flashcards

Snow A Flashcards

1
Q

what is air pressure

A

the weight of the air above you

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2
Q

what else can you call a high pressure system

A

anticyclone

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3
Q

what is a high pressure system

A

region where air pressure is higher than the surrounding regions

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4
Q

what is better for outdoor activities, high pressure or low pressure?

A

High pressure

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5
Q

on a pressure map, what does the H mean?

A

surface high, if the surface was reduced to sea level

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6
Q

how is pressure shown on a pressure map

A

isobars

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7
Q

what is an isobar

A

lines and contours connecting areas that have the same pressure

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8
Q

what is a high pressure ridge

A

areas of high pressure that extend out of high pressure centers, partially enclosed circle on map

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9
Q

what is a low pressure trough

A

area of low pressure around a low pressure center

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10
Q

why does high pressure bring good weather?

A

winds diverge away from the centre of high pressure, and winds tend to be weaker because pressure differences are weaker.

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11
Q

What is the Coriolis effect

A

wind spirals away in a clockwise circulation

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12
Q

What weather phenomenons are associated with high pressure systems

A

dry conditions, clear skies, lack of precipitation.

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13
Q

insolation

A

incoming solar radiation (ex. visible light or UV rays)

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14
Q

pressure ____ with height in the atmosphere

A

decreases.

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15
Q

how much sunlight does snow reflect?

A

90%

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16
Q

flat light

A

increasing high clouds that diffuse the sunlight, affecting depth perception on hills

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17
Q

what can pressure-level maps be used for

A

looking at weather variables at heights above sea-level elevation

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18
Q

what is the unit for atmospheric pressure

A

kPa kilopascals or hPa hectopascals

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19
Q

what is the pressure at sea-level

A

usually about 100.0 kPa

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20
Q

what is the pressure mid-mountain

A

85 kPa

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21
Q

analysis map

A

pressure map showing when the map was started

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22
Q

forecast map

A

showing pressure in the future

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23
Q

how is wind displayed on a weather map

A

wind barbs

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24
Q

what do the feathers on the wind barb tell you

A

wind speed, half barbs are 10km/h and long ones are 20 km/h

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25
Q

what does the bare end of a wind barb tell you

A

the direction the wind is going

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26
Q

what does a wind map exclude

A

friction

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27
Q

what are winds like where there is a weak pressure gradient

A

light winds

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28
Q

how can you tell if a pressure gradient is weak

A

the isobars are far apart

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29
Q

when does high pressure not mean light winds

A

when there are outflow winds

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30
Q

what is a low-level wind map

A

shows wind speed and direction using barbs and coloured vectors.

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31
Q

what are the hazards of light winds

A

none

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32
Q

interpolation

A

estimating the temperature between two locations of known temperatures.

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33
Q

What is free air temperature

A

the temperature at a particular level of the atmosphere, assuming no heat or cooling effects from the surface

34
Q

what happens to temperature under dry adiabatic conditions?

A

temperature decreases with height at 10 degrees per 100 metres.

35
Q

What are wet adiabatic conditions

A

when air is saturated 100% humidity, temperature decreases more slowly with height at 6 degrees per 100 m

36
Q

when can you assume wet adiabatic conditions

A

when humidity is greater than 80%

37
Q

what is a temperature inversion

A

when temperature increases with height, like in valleys in the overnight period in winter.

38
Q

what are the two steps of temperature forecasting

A

1) attain temperature at location from pressure map

2) adjust temperature based on heating or cooling of surface

39
Q

in the troposphere what is the initial source of heating and cooling

A

ground surface

40
Q

what factors effect heating or cooling

A

the sun, cloud cover, wind speed

41
Q

what is snow metamorphism/evolution of the snowpack

A

how the snow on the ground changes after it falls

42
Q

what does snow metamorphism influence

A

avalanche danger

43
Q

what is a gradient

A

a change in property over a distance (vertical or horizontal)

44
Q

what is the temperature at the bottom of the snowpack

A

about 0 degrees because of the warmth of the earth.

45
Q

what is the coldest point of the snowpack

A

the top

46
Q

What is the most important factor that influences the evolution of the snowpack

A

snowpack temperature gradient

47
Q

what is vapour pressure

A

part of air pressure due to the amount of air that is water vapour.

48
Q

how is vapour pressure affected in the snowpack

A

higher the temperature, the greater the vapour pressure

49
Q

What are the forms of snow crystals

A
  1. faceted crystals

2. rounded crystals

50
Q

When are faceted crystals produced

A

when a strong temperature gradient exists, as the crystals go quickly. temperature gradient larger than 1 degree per 10 cm depth.

51
Q

How much space is in between faceted crystals

A

lots

52
Q

when are rounded crystals produced

A

when temperature gradients are weak, crystals grow slowly, temperature gradient less than 1 degree per 10 cm depth

53
Q

how much space is between rounded crystals

A

little

54
Q

how does crystal type affect avalanche danger

A
  • faceted crystals are weakly bonded so snowpack is more unstable.
  • rounded crystals are strongly bonded so snowpack is more stable.
55
Q

deposition

A

substance overgoes phase change from gas to solid, without liquid in between.

56
Q

dewpoint temperature

A

air temperature at which water vapour condenses to liquid droplets while being cooled

57
Q

frostpoint temperature

A

dewpoint temperature if the air is below 0 degrees celsius.

58
Q

surface hoar

A

frozen version of dew, crystals on the top of the snowpack

59
Q

what is needed for surface hoar to form

A
  • clear skies
  • calm winds
  • strong temperature inversion
60
Q

hazards of surface hoar

A

avalanches

61
Q

what destroys surface hoar

A
  • sunlight/warm air
  • strong winds
  • melting
  • rain
62
Q

snow pits

A

dug by backcountry skiers to find info on layers in snow pack

63
Q

the handhardness test

A

applies pressure to each layer using a hand, one finger, pencil or knife.

64
Q

What are the snowpack layers

A
  • weakly bonded snow layers
  • strong bonded layers
  • crust layers
65
Q

snow weak layer

A

has undergone faceting, lower density, more likely to collapse. at surface.

66
Q

snow strong layer

A

old stellar dendrites that are rounded, less likely to collapse.

67
Q

crust snow layer

A

rain on snow forming a rain crust, or melting to form a sun crust.

68
Q

storm snow

A

snow that is falling or fell within the last 48 hours. unstable.

69
Q

what is a comfortable ski temperature range

A

-8 degrees to +3 degrees

70
Q

hazards of cold skiing temperatures

A
  • frostbite
  • hypothermia
  • wind chill
  • avalanches
71
Q

hazards of warm skiing temperatures

A
  • anything above 5 degrees
  • can freeze cotton clothing
  • strong solar insolation
  • hyperthermia
72
Q

statically stable

A

cool air beneath a layer of warm air

73
Q

are inversions stable

A

yes

74
Q

what is evidence of a temperature inversion

A

fog

75
Q

capping inversion

A

air rising only travels one inversion layer

76
Q

subsidence

A

sinking air of a high pressure system

77
Q

climate

A

prevailing weather conditions

78
Q

3 types of snow climates

A
  • coastal
  • transitional
  • continental
79
Q

coastal snow climate

A
  • frequent snowfall
  • high density of fallen snow
  • warm temperatures
  • coastal location
  • deep snowpack
  • avalanches after storms
  • low avalanche danger
80
Q

transitional snow climate

A
  • frequent snowfall
  • moderate density
  • moderate depth
  • low avalanche danger
81
Q

continental snow climate

A
  • low snowfall
  • low density snowfall
  • cold temperatures
  • inland location far from coast
  • shallow snowpack
  • persistent weak layers
  • high avalanche danger

ASTC (6 decks)

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