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Snow A Flashcards

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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
what does the bare end of a wind barb tell you
the direction the wind is going
26
what does a wind map exclude
friction
27
what are winds like where there is a weak pressure gradient
light winds
28
how can you tell if a pressure gradient is weak
the isobars are far apart
29
when does high pressure not mean light winds
when there are outflow winds
30
what is a low-level wind map
shows wind speed and direction using barbs and coloured vectors.
31
what are the hazards of light winds
none
32
interpolation
estimating the temperature between two locations of known temperatures.
33
What is free air temperature
the temperature at a particular level of the atmosphere, assuming no heat or cooling effects from the surface
34
what happens to temperature under dry adiabatic conditions?
temperature decreases with height at 10 degrees per 100 metres.
35
What are wet adiabatic conditions
when air is saturated 100% humidity, temperature decreases more slowly with height at 6 degrees per 100 m
36
when can you assume wet adiabatic conditions
when humidity is greater than 80%
37
what is a temperature inversion
when temperature increases with height, like in valleys in the overnight period in winter.
38
what are the two steps of temperature forecasting
1) attain temperature at location from pressure map | 2) adjust temperature based on heating or cooling of surface
39
in the troposphere what is the initial source of heating and cooling
ground surface
40
what factors effect heating or cooling
the sun, cloud cover, wind speed
41
what is snow metamorphism/evolution of the snowpack
how the snow on the ground changes after it falls
42
what does snow metamorphism influence
avalanche danger
43
what is a gradient
a change in property over a distance (vertical or horizontal)
44
what is the temperature at the bottom of the snowpack
about 0 degrees because of the warmth of the earth.
45
what is the coldest point of the snowpack
the top
46
What is the most important factor that influences the evolution of the snowpack
snowpack temperature gradient
47
what is vapour pressure
part of air pressure due to the amount of air that is water vapour.
48
how is vapour pressure affected in the snowpack
higher the temperature, the greater the vapour pressure
49
What are the forms of snow crystals
1. faceted crystals | 2. rounded crystals
50
When are faceted crystals produced
when a strong temperature gradient exists, as the crystals go quickly. temperature gradient larger than 1 degree per 10 cm depth.
51
How much space is in between faceted crystals
lots
52
when are rounded crystals produced
when temperature gradients are weak, crystals grow slowly, temperature gradient less than 1 degree per 10 cm depth
53
how much space is between rounded crystals
little
54
how does crystal type affect avalanche danger
- faceted crystals are weakly bonded so snowpack is more unstable. - rounded crystals are strongly bonded so snowpack is more stable.
55
deposition
substance overgoes phase change from gas to solid, without liquid in between.
56
dewpoint temperature
air temperature at which water vapour condenses to liquid droplets while being cooled
57
frostpoint temperature
dewpoint temperature if the air is below 0 degrees celsius.
58
surface hoar
frozen version of dew, crystals on the top of the snowpack
59
what is needed for surface hoar to form
- clear skies - calm winds - strong temperature inversion
60
hazards of surface hoar
avalanches
61
what destroys surface hoar
- sunlight/warm air - strong winds - melting - rain
62
snow pits
dug by backcountry skiers to find info on layers in snow pack
63
the handhardness test
applies pressure to each layer using a hand, one finger, pencil or knife.
64
What are the snowpack layers
- weakly bonded snow layers - strong bonded layers - crust layers
65
snow weak layer
has undergone faceting, lower density, more likely to collapse. at surface.
66
snow strong layer
old stellar dendrites that are rounded, less likely to collapse.
67
crust snow layer
rain on snow forming a rain crust, or melting to form a sun crust.
68
storm snow
snow that is falling or fell within the last 48 hours. unstable.
69
what is a comfortable ski temperature range
-8 degrees to +3 degrees
70
hazards of cold skiing temperatures
- frostbite - hypothermia - wind chill - avalanches
71
hazards of warm skiing temperatures
- anything above 5 degrees - can freeze cotton clothing - strong solar insolation - hyperthermia
72
statically stable
cool air beneath a layer of warm air
73
are inversions stable
yes
74
what is evidence of a temperature inversion
fog
75
capping inversion
air rising only travels one inversion layer
76
subsidence
sinking air of a high pressure system
77
climate
prevailing weather conditions
78
3 types of snow climates
- coastal - transitional - continental
79
coastal snow climate
- frequent snowfall - high density of fallen snow - warm temperatures - coastal location - deep snowpack - avalanches after storms - low avalanche danger
80
transitional snow climate
- frequent snowfall - moderate density - moderate depth - low avalanche danger
81
continental snow climate
- 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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