Lecture #3-4 [Weather and Climate]

Question 1

weather vs. climate

Answer 1

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.

Question 2

The Atmosphere

Answer 2

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

Question 3

composition

Answer 3

gases, particulate matter

Question 4

Thermal layers of atmosphere (5)

Answer 4

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

Question 5

Pressure

Answer 5

• 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

Question 6

millibar (mb)

Answer 6

most common unit for atmospheric pressure

Question 7

isobars

Answer 7

lines that connect points of equal pressure

Question 8

how does wind move

Answer 8

air flows from H to L pressure

Question 9

Direction of wind goverened by which three factors

Answer 9

1. pressure gradient force
2. coriolis effect
3. friction

Question 10

Pressure Gradient Force

Answer 10

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

Question 11

coriolis effect

Answer 11

• 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

Question 12

Pressure Gradient + Coriolis

Answer 12

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

Question 13

Friction does what

Answer 13

reduces wind speed

reduces coriolis effect

upsets geostrophic wind flow

winds move across isobars at an angle

Question 14

Anticyclone vs Cyclone

Answer 14

winds spiral outwards from high pressure area clockwise (anticyclone)

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

Question 15

Wind speed

Answer 15

steep pressure gradient = fast moving winds

gradual pressure gradient= slow moving winds

Question 16

Buoyancy

Answer 16

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

Question 17

stability

Answer 17

stable air is non-buoyant (resists vertical movement)

in atmosphere: cold air beneath warm air

• temperature inversion
• cold winter night

Question 18

Instability

Answer 18

mass of air heated

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

Question 19

Equilibrium level

Answer 19

altitude where density, temp= surrounding air

while rising, air cools adiabatically

Question 20

Adiabatic cooling

Answer 20

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

Question 21

Adiabatic warming

Answer 21

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

Question 22

what is a visual determinatiopn of stability

Answer 22

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

Question 23

stable air

Answer 23

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

Question 24

unstable air

Answer 24

• buoyant
• rises without outside force
• clouds: cumuloform
• precip: showery

Question 25

Air mass

Answer 25

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

Question 26

warm fornts

Answer 26

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.]

Question 27

Cold fronts

Answer 27

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.]

Question 28

Mid-latitude cyclones

Answer 28

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

Question 29

Northern hemisphere mid latitude cyclones

Answer 29

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

Question 30

Mid latitude anticyclones

Answer 30

migratory H-pressure cell [w to e] air subsiding, diverging, clockwise rotation no fronts weather clear and dry summer= warm temps; winter= very cold

Question 31

Hurricanes

Answer 31

tropical cyclones very low pressure centres: steep pressure gradients outward from centre strong winds spiraling inward must be >119 km/h

Question 32

Hurricanes vs. Mid-latitude cyclones

Answer 32

all warm air; no fronts much smaller eye where weather is calm strongest winds at eye wall

Question 33

Global atmospheric circulation

Answer 33

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

Question 34

Hadley cells

Answer 34

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

Question 35

Surface components of atmospheric circulation

Answer 35

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

Question 36

subtropical highs

Answer 36

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

Question 37

Trade winds

Answer 37

equator-ward side od STHs diverge toward W and toward equator 25*N- 25*S easterly warm, drying winds capable of holding lots of moisture don't release moisture unless

Question 38

intertropical convergence zone

Answer 38

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

Question 39

Westerlies

Answer 39

30*-60* n and s surface winds: all directions upper atmosphere winds: geostrophic, prominently WE polar front jet stream sub trop jet stream

Question 40

Polar front jet stream

Answer 40

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

Question 41

Polar Highs

Answer 41

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

Question 42

Polar easterlies

Answer 42

winds move EW occupy area between polar high and 60* cold and dry

Question 43

Subpolar lows

Answer 43

l pressure at 50-60* n and s rising air clouds precipitation generally stormy conditions

Question 44

Local winds that affect BC

Answer 44

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 ```

Question 45

Valley breezes

Answer 45

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

Question 46

Mountain Breezes

Answer 46

night: mountain slopes lose heat rapidly adjacent air chills and creates H pressure air sinks downslope into valley

Question 47

Chinook winds

Answer 47

steep pressure gradient air flows from windward to leeward side warm and dry has lost moisture adiabatic warming

Question 48

Orographic lifting

Answer 48

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

Question 49

El nino- southern oscillation (ENSO) and La Nina

Answer 49

[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

Question 50

Pacific Decadal Oscillation (PDO)

Answer 50

-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