Download Weather Unit: Chapters 13, 14

Weather Unit:
Chapters 13, 14

Sec.13.1 A Closer look at Earth

Globe
– Three dimensional model of the earth.
– Earth is tilted
23.5 degrees
Influences on weather
1.
2.
Land forms
Water
– Covers approx. 70% of earth
3.
Atmosphere
– Contains air , water vapour, dust,
chemicals….
Weather vs. Climate

Weather
– Conditions outside considered from day to
day

Climate
– Weather conditions of an area averaged
over years.
Global Geography

Longitude
– Angle measured east or west from 0
degrees which runs through Greenwich,
England.
– Prime meridian: 0 degrees longitude

Latitude
– Angle measured north or south of the
equator
 Latitudes
Longitudes 
Lines Of Latitude

Tropic of Cancer:
– 23.5 degrees north
– Most northern location of suns vertical rays
(overhead) on June 21 or 22

Tropic of Capricorn
– 23.5 degrees south
– Most southern location of suns vertical rays
(overhead) on Dec 21 or 22

The tropics
– Lay between the tropic of cancer and Capricorn.
To Do: pg503 #1-9 (omit #5)
Earth’s Energy Balance:

Radiation
– Transfer of electrons by waves.
(terms)
 Electromagnetic
spectrum
– Set of waves that can travel through empty
space at the speed of light.
– Longest to shortest:
radio
microwaves
infrared
visible
ultraviolet
x-ray
gamma
 Visible light:
– colors of the spectrum
– Red/orange: long wave, low frequency
– Violet/blue: short waves, high frequency
– ROYGBIV short --long
 Conduction:
–the transfer of energy through
collision of particles
–Heat causes particles to vibrate
faster, collide more…object heats
up.
 Convection:
– The vertical transfer
of energy by movement
of particles in a fluid.
– Particles gain energy, spread out, as
density lowers, it rises. It then cools,
density increases, it falls. A current is
made.
Summary:
 Advection:
– the horizontal transfer of energy by
the movement of particles in a fluid
 Heat
Capacity:
– how much heat a substance requires
to increase its temperature or how
much heat it releases as it cools.
• Pavement: heats up quickly, cools quickly, it
has a low heat capacity
• Water, air: heats up slowly, cools down slowly, it
has a high heat capacity

Heat Sink:
– Any object or material that absorbs energy
and becomes warmer
– ex. Atmosphere, ocean. They “hold” the
heat”
– Influence climates.
• Ex. NL proximity to ocean = cool summers/mild
winters
Sec 13.3 Seasons /angle of sun

Seasons and weather system are due
to earths rotation at a 23.5 tilt.

Seasons are the result of the angle the
sun hits each hemisphere.

June 21st:
– Summer solstice (warm)
– Longest day of year in northern
hemisphere (which is at maximum tilt
toward sun)

Dec 21st
– Winter solstice (cold)
– Shortest day of year in northern
hemisphere (which is at maximum tilt away
from sun)

March 21, September 23
– Equinoxes (autumn, spring)
– Sun hits directly at equator
– Length of day time= night time
Seasons:
March 21
June21
Dec 21
September 23
Sec 13.4 The Atmosphere
important for life and weather
 Is the blanket of air and moisture that
surround the earth.
 Increase in altitude = decrease in
density.Is most dense at sea level.
Why?

• Molecules are pressed together by weight of
molecules above.

Atmosphere:
– 78% nitrogen
– 21%oxygen
– 1% other gases (elements and water vapour)

Atmospheric layers:
– Exosphere (outer space)
– Thermsophere (also called; aurora, ionosphere)
• mesopause
– Mesosphere
• stratopause
– Stratosphere
• tropopause
– Troposphere (closest to ground)

Pauses are “separating layers”
Layers of the Atmosphere:

Troposphere:
– touches earth
– 16-18 Km thick at equator (only 8Km at
poles since cold air contracts)
– Contains “weather”.
– Increased altitude = decreased
temperature
– Tropopause: thin separating boundary.

Stratosphere:
–
–
–
–

Little moisture (not much weather)
12-50 Km above earth
Contains ozone layer.
Temps increase with altitude.
Mesosphere:
– Middle layer
– Not much gas
– Temperatures decrease fast with altitude
increases.
– 50-90Km above earth

Thermosphere
– Low density
– High temperature molecules (high energy)
– 90-500Km above earth.
– Reflects radio waves resulting in Auroras
Borealis (northern lights)
• High energy radiation from sun causes particles
to become electrically charged

Exosphere:
– Outer space
– “Almost” a vacuum

Memory Trick!
– Try Stealing Mels Thermos
– Tropos strato meso thermo…spheres

Temperature Gradient
– Change in temp. over a distance
– In troposphere 1000m up = -6o
– i.e.. There is a 6 degree drop with every
1000m altitude increase
Temperature changes in the layers of
the atmosphere:
Atmosphere and life
Provides O2 and CO2
 Absorbs UV radiation from sun (in
ozone layer)
 Water cycle
 Protects against meteors
 Regulates earths temperature (traps
heat, circulates it)

Atmospheric Pressure
Pressure air exerts as gravity pulls it
toward earth
 Highest at sea level
 Decreases with altitude
 Depends on whether air is rising or
dropping.


Pressure gradient
– Measure of amount of atmospheric
pressure change across a distance
– Vertical pressure gradients
• Pressure decreases when altitude increases
Altitude
Altitude 
Pressure 
– Horizontal pressure gradients
• Result of winds
– Low wind speed= low pressure
– High wind speed = high pressure
Low pressure area
High Pressure area

Aneroid Barometer
– Measures atmospheric pressure
– No liquid in it
– Has thin metal walls/levers that are pressure
sensitive
– Fig5, pg 512
Studying weather:

Weather balloons
– Carry radiosonde high into atmosphere
– Radiosonde
• Device that has sensors that measure
temperature, atmospheric pressure, water
vapour)
• It sends radio waves back to ground station
– Radar systems track balloon to find wind
speed and direction
Sec 13.6 Prevailing Winds

Wind
– Movement of air in the atmosphere
• Regional small area
• Prevailing large area
Coriolis Effect

Apparent shift in direction (curves) of a
moving object due to the rotation of the earth.
 First studied by Gaspard de Coriolis (French
mathematician)
 Ocean currents and prevailing winds appear
to curve as a result of this rotation
– In north= rotates to right
– In south = rotates to left
Coriolis effect
Coriolis Effect
Prevailing Winds
Polar easterlies
 Mid latitude westerlies
 Northeast trade winds
 Southeast trade winds
 Jet streams :

•
•
•
•
Flow east
In upper troposphere
High speeds
Steer weather systems (H/L pressures)
Jet Streams (
Prevailing Winds:
Northern
hemisphere=
clockwise
Southern =
counterclockwis
e

Causes of prevailing winds
– Convection currents:
• Air is moved by pressure gradients and the
Coriolis effect. It rises, move laterally, and falls.
This circulation is a convection cell (Hadley
cell)
– Eastward rotation of earth
Convection currents:
 Hadley cell
Northern Convection Currents:

At equator:
– Sun warms earth, air…..
– Warm air expands, rises and travels north in
troposphere
– low pressure area is created.

At 300
– Air cools, contracts, is denser and sinks.
– This makes a high pressure area which pushes air
toward the low pressure equator.

Northeast trade wind is formed!!!!!

At 300
– Some air pushed toward low pressure
areas at 60degrees North
– This low pressure area was formed by midlatitude convection currents formed when
warm air meets cold polar air.

Mid- Latitude westerlies are formed!!!

Near poles:
– Cold air sinks, makes high pressure area.
– This creates Polar Easterlies.
Effect of Prevailing winds:
Distribute solar energy from equator to
poles
 Move cold air to equator
 Carry moisture (make precipitation)


At Equator:
– Equatorial convection currents meet and
rise.
– Weather is rainy.

30 degrees north:
– Cold sinking dry air creates deserts
• Gobi desert;asia,
• Great Basin, sonaora desert in North America
• Sahara, Mojava in South Africa

60degrees north:
– Air systems meet
– Results in cloud, precipitation, strong winds
storms
– Why? Hugh temperature differences: Artic
has no sun 6 months of year. Gets very
cold fast.
Prevailing winds
Sec 13.8 The Hydrosphere

All earths water
– Salty= 97.5 %
– Fresh = 2.5%
• 87.3% glaciers
• 12.3% underground
• 0.4% surface, atmosphere
(90 % lakes, 9% atmosphere, 1% rivers)

Weather depends on water changing
state (S, L, G)

Water cycle pg 523
– Sublimation (iceliquid)
– Evaporation( liquid  vapour)
– Transpiration (water in plants  vapour)
– Precipitation (vapour rain, hail, snow…)
– Condensation (vapour to liquid)
Water Cycle:
Sec 13.9 Ocean Currents
Movement of earths water, distributes
energy.
 Similar to a conveyor belt.

• Moves cold water from poles to equator.
• Moves warm water from equator to poles.

Weather depends on temperature of
water in current.
• Labrador Current: is cold, keeps NL cool
• Gulf Stream: is warm, keeps Atlantic
provinces warm
Ocean Currents
Causes of Currents

Convection currents (fig 2 pg 526)
• Sun heats up equator
• Water is warm , less dense, rises moves north
and south.
• Cold water replaces it from below.

Earths Rotation
• Coriolis effect

Heat Capacity of water
• Is high, it is a heat sink (warms/cools slowly)

Shape of land
– Directs water movements (earth rotates east
so……)
• Currents on west of land masses are narrow and fast
• Currents on east of land masses are broad and slow
• Antarctic circumpolar current doesn’t hit land.

Salt:
– Salt water is dense, sinks, is replaced by less
dense water.
– This occurs in gulf stream, water evaporates
leaving behind more salty water.
Effect of Ocean Current in North
Atlantic
Gulf stream bring warm water to
Maritimes
 Labrador current brings cold water.
 They meet = FOG
 Gulf stream keeps, Norway, Iceland and
England warmer than expected.

Sec 13.11 Clouds and Fog

Water cycle and rain
– Sun’s energy is absorbed by liquid water.
– Molecules speed up , change to vapour
and rise.
– Vapours rise to and altitude where they
cool, condense and fall as precipitation.
Cloud Formation

Convection clouds
– Ground air warms, rises bringing with it
water vapour.
– At high elevations, air expands(less
pressure) and cools and condenses into
small droplets making clouds.

Frontal Clouds
– Front of a large moving air mass hits
another mass of different temperatures.
– Warm moist air rises (less dense) .
– The air expands, cools and droplets form
(clouds).

Orographic Clouds:
– Air moves up a mountain, expands cools,
moisture condenses making clouds.
Animations of Warm Fronts
and Cold Fronts forming
clouds: http://meted.ucar.edu/mesoprim/bandedprecip/pri
nt.htm#3.2

Fog
– Clouds at ground level
– Air at surface cools and droplets condense
making clouds = fog.
– Warm air cools over snow, ponds….
Moisture condenses = fog
Cloud types

Cumulus Clouds:
– Billowing, round
– Grow vertically
– Indicate unstable weather

Stratus clouds:
– Flat, layered
– Grow horizonatlly
– Indicate stable conditions

Nimbus clouds:
– Dark, hold rain.
See fig 7 pg 533 for low, med, high level
clouds.
 Cirrus = high altitude
 Alto = medium altitude

Factors that affect our daily
weather: pg 537
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Solar energy
Clouds
Earths rotation
Jet stream
Prevailing winds
Ocean currents
Land masses
The hydrosphere