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Geography > Lecture #3-4 [Weather and Climate] > Flashcards

Lecture #3-4 [Weather and Climate] Flashcards

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1
Q

weather vs. climate

A

weather = specific condition of the atmosphere at a particular place and time. It is measured in terms of variables including

Climate= a statisical characterization of the weather, averaged over many years.

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2
Q

The Atmosphere

A
  • supplies oxygen and carbon dioxide
  • insulates against temperature extremes
  • shields uv radiation
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3
Q

composition

A

gases, particulate matter

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4
Q

Thermal layers of atmosphere (5)

A
  1. troposphere (~18 km)
  2. Stratosphere (18-48 km)
  3. Mesophere (48-80 km)
  4. Thermosphere (80 km)
  5. Exosphere (into space)
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5
Q

Pressure

A
  • basically, the weight of overlying air
  • the taller the column of air above an object, the more pressure exerted
  • Highest at sea level (1kg/cm2) decreases with increasing altitude
  • Not a constant change with altitude: decreases at a decreasing rate
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6
Q

millibar (mb)

A

most common unit for atmospheric pressure

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7
Q

isobars

A

lines that connect points of equal pressure

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8
Q

how does wind move

A

air flows from H to L pressure

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9
Q

Direction of wind goverened by which three factors

A
  1. pressure gradient force
  2. coriolis effect
  3. friction
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10
Q

Pressure Gradient Force

A
  • path of least resistance
  • air flows at right angles to isobars
  • high pressure= descending diverging
  • low pressure= ascending+converging
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11
Q

coriolis effect

A
  • deflects any object that flies or flows from straight path
  • due to earth’s rotation eastward
  • deflects to the right in N. Hem; left in S. Hem
  • maximum at poles; zero at equator
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12
Q

Pressure Gradient + Coriolis

A

coriolis effect prevents surface winds from moving along pressure gradient

acts in the opposite direction to P.G force in upper troposphere

produces geostrophic winds: travel parralel to isobars

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13
Q

Friction does what

A

reduces wind speed

reduces coriolis effect

upsets geostrophic wind flow

winds move across isobars at an angle

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14
Q

Anticyclone vs Cyclone

A

winds spiral outwards from high pressure area clockwise (anticyclone)

winds spiral inwards into low pressure areas counterclockwise (cyclone)``

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15
Q

Wind speed

A

steep pressure gradient = fast moving winds

gradual pressure gradient= slow moving winds

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16
Q

Buoyancy

A

the tendency of any object to rise in a fluid

warm air parcel= less dense than surrounding air RISES

cool air parcel=denser than surrounding air SINKS

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17
Q

stability

A

stable air is non-buoyant (resists vertical movement)

in atmosphere: cold air beneath warm air

  • temperature inversion
  • cold winter night
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18
Q

Instability

A

mass of air heated

  • becomes unstable
  • a warm summer afternoon or at the equator
  • air rises until it reaches equilibrium level
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19
Q

Equilibrium level

A

altitude where density, temp= surrounding air

while rising, air cools adiabatically

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20
Q

Adiabatic cooling

A

rising air, expansion because of less pressure, molecules spread, less collisions, drop in temp of air parcel

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21
Q

Adiabatic warming

A

descending air, compression because of more pressure, molecules get closer, more collisions, rise in temperature of air parcel

22
Q

what is a visual determinatiopn of stability

A

clouds

unstable air, rising air ans vertical clouds

cumulous clouds=unstable air

stratiform clouds= stable air forced to rise

cloudless sky = stable air that is immobile

23
Q

stable air

A
  • non buoyant
  • remains immobile unless forced to rise
  • clouds: stratiform, cirriform
  • precip: drizzle
24
Q

unstable air

A
  • buoyant
  • rises without outside force
  • clouds: cumuloform
  • precip: showery
25
Q

Air mass

A 
-a distinct parcel of air
>1600 km across
-homogeneous with respect to
-temp, humidity, stability
-source regions= where air masses originate
26
Q

warm fornts

A

advancing warm air

gentle slope

warm air ascends over retreating colder air

air cools adiabatically; clouds and precip

gradual uplift, clouds and precip, can last for days

[pressure decreases, cirrus clouds, thicker and lower clouds, pressure decreases,air is warmer and humid when parcel passes.]

27
Q

Cold fronts

A

advancing cold air

hugs ground: dense air

steep face because of friction

causes rapid uplifiting of warm air as cold air hits it

rapid uplfit makes warm air very unstable

blustery & violent weather

higher intensity and shorter duration

[high cirrus clouds 1/2 days before, temp drops, fall in pressure, after air passes the air is colder.]

28
Q

Mid-latitude cyclones

A 
westerly winds
almost always move to east
day to day weather changes
migratory L-pressure systems
air mass convergence 35-70 degrees lat
29
Q

Northern hemisphere mid latitude cyclones

A

converging counter clock wise

cool air from N warm air from S

convergence of 2 air masses; 2 fronts

cold front [center to SW]

warm front [center to NE]

2 zones of clouds and precip

30
Q

Mid latitude anticyclones

A

migratory H-pressure cell [w to e]

air subsiding, diverging, clockwise rotation

no fronts

weather clear and dry

summer= warm temps; winter= very cold

31
Q

Hurricanes

A

tropical cyclones

very low pressure centres: steep pressure gradients outward from centre

strong winds spiraling inward

must be >119 km/h

32
Q

Hurricanes vs. Mid-latitude cyclones

A

all warm air; no fronts

much smaller

eye where weather is calm

strongest winds at eye wall

33
Q

Global atmospheric circulation

A

without rotation or even land and water distribution

  • excess radiation at equator- creates low pressure belt around the world
  • poles: high pressure
  • surface winds would travel along pressure gradient
  • air would rise at equator, flow toward poles, sink into polar highs
34
Q

Hadley cells

A

warm air rises at equator

creates low pressure

ascends and cools

moves poleward

begins descending at 30* N and S

creates high pressure

flows back toward equator

35
Q

Surface components of atmospheric circulation

A
  1. polar high
  2. polar easterlies
  3. subpolar low
  4. westerlies
  5. sub trop high
  6. trade winds
  7. inter trop convergence zone
36
Q

subtropical highs

A

h pressure belt at 30*

huge anticyclones

develop from descending hadley cell air

weather warm, clear, calm little rain

desert locations

“horse latitude”

source of tradewinds and westerlies

37
Q

Trade winds

A

equator-ward side od STHs

diverge toward W and toward equator

25N- 25S

easterly

warm, drying winds

capable of holding lots of moisture

don’t release moisture unless

38
Q

intertropical convergence zone

A

air from 3 hemispheres meets

where NE and SW trades come together

doldrums

weak airflow erratic winds

L pressure belt circling globe

over oceans, defined cloud band

over continents, associated with T-storms

39
Q

Westerlies

A

30-60 n and s

surface winds: all directions

upper atmosphere winds: geostrophic, prominently WE

polar front jet stream

sub trop jet stream

40
Q

Polar front jet stream

A

9-12 km high in troposphere

basically WE but shifts regularyly

curves= rossby waves [separate cold polar air from warm tropical air]

influence on surface weather

41
Q

Polar Highs

A

H pressure over both poles

antarctic high
-strong and persistent

arctic high
-less pronounces

anticyclonic air flow

air sinks into high pressure and diverges near surface

42
Q

Polar easterlies

A

winds move EW

occupy area between polar high and 60*

cold and dry

43
Q

Subpolar lows

A

l pressure at 50-60* n and s

rising air

clouds

precipitation

generally stormy conditions

44
Q

Local winds that affect BC

A

sea and land breezes

tropical coastlines, midlatitudes in summer

day= sea breeze (coming from sea)

night= land breeze (coming from land)

During day, land warms up fast
heats air above
air expands, rises creates L pressure 
breezes blow in from water
at night land cools more quickly 
relatively higher pressure over land
45
Q

Valley breezes

A

day: radiation from land

mountain slope air heats up faster than valleys

heated air rises, creates L pressure, air flows upslope from H to L pressure

46
Q

Mountain Breezes

A

night: mountain slopes lose heat rapidly

adjacent air chills and creates H pressure

air sinks downslope into valley

47
Q

Chinook winds

A

steep pressure gradient

air flows from windward to leeward side

warm and dry has lost moisture

adiabatic warming

48
Q

Orographic lifting

A

air forced upslope

if ascending air is cooled to dewpoint, precipitation results

as air moves down leeward side, it warms, rain stops

rain shadow= dry area on leeward side

49
Q

El nino- southern oscillation (ENSO) and La Nina

A

[El Nino] warming of the surface equatorial ocean surface off the coast of southern america

[La Nina] conditions involve upwelling of cold water in the same region

In BC, winters following the oset of an El Nino event are generally warmer and drier normal and La Nina winters are generally cooler and wetter

It looks like we are experiencing an el Nino year in 2019

50
Q

Pacific Decadal Oscillation (PDO)

A

-warm phase of the PDO is characterized by below-normal sea surface temperatures in the central and western north pacific and unusually high ones along the west coast of North America

positives PDO phases are associated with warmer temperatures throughout western canada and with less precipitation in the mountains and interior, which also reduce the snowpack

currently in a positive phase

Geography (9 decks)

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