Download Chapter 7 Part Ib: Weather and Climate

Chapter 7 Part Ib: Weather and Climate:
Coriolis Effect, Convection Cells, and
Global Winds
Major Factors Influencing Climate
1. Composition of the Atmosphere and
Greenhouse Effect
2. Incoming Solar Radiation Angle: leads to
uneven heating of troposphere from beneath;
3. Air circulation patterns: determined by
- Uneven heating of Earth's surface, due to Earth’s tilt;
- Seasonal changes due to Earth's tilt on axis & revolution
about the sun;
- Location of land and water masses (land heats up and
cools down faster than water)
- Coriolis Effect: caused by Earth's rotation on its axis;
- Large scale convection cells
4. Ocean currents (Part II)
- influenced by factors that influence air circulation plus
differences in water density.
5. Milankovitch Cycles (Part II): long–term variations
in incoming solar energy
Wind and the Coriolis Effect
• What direction does the Earth
rotate?
• View a globe rotating in this
direction.
• What is the direction of the motion
(clockwise vs. counterclockwise)
when viewed from the Northern
Hemisphere ?
• What is the direction of the motion
(clockwise vs. counterclockwise)
when viewed from the Southern
Hemisphere ?
• Why?
Rotational Velocity
Due to the different
circumferences at
different points on the
earth, the rotational
velocity varies from 1700
km/hr at the equator to
________ at the poles.
Rotational speed decreases by the cosine of your latitude so
that Seattle, which has a latitude of 47.6 degrees, cos(47.6) =
.674. The speed is .674 x 1670 = _______ km/hr. You can use
this formula to find the speed of rotation at any latitude.
•http//www.youtube.com/watch?v=9QDKnQm_poI (first 30 sec only)
Coriolis Effect
• The _______________ deflection of
a moving object when viewed from
a _________ frame of reference.
• as Earth rotates, surface turns
__________ beneath air masses
near __________ than near poles,
resulting in deflection of wind
• Northern Hemisphere: winds are
deflected to the _______.
• Southern Hemisphere: winds are
deflected to the _______.
http://www.classzone.com/books/earth_science/terc/content/v
isualizations/es1904/es1904page01.cfm?chapter_no=19
http://www.youtube.com/watch?v=aeY9tY9vKgs watch to 2 min, 45 sec
Northern Hemisphere Circulation Patterns:
http://www.classzone.com/books/earth_science/terc/content/visualiz
ations/es1905/es1905page01.cfm?chapter_no=visualization
Winds blow ________________Winds blow __________________
______from high pressure areas ____ towards low pressure areas
H
L
Hurricanes
Hurricanes rotate around
______ pressure, so
Northern Hemisphere
hurricanes rotate
counterclockwise
Southern Hemisphere
hurricanes (cyclones)
rotate clockwise
http://www.youtube.com/watch?v=i2mec3vgeaI
Pressure and Precipitation
• High pressure is associated
with ____________
--Rising air pressure means an
area of high pressure is
moving in = _______ weather
High Pressure
• Low pressure is associated
with _________
--Falling air pressure means
an area of low pressure is
moving in = _______
weather
Low Pressure
H
In summer, the Pacific Northwest
is dominated by High Pressure off
our coast (the “Pacific High”),
which brings cool, dry air down
from Canada
L
In winter, the Pacific Northwest
is dominated by Low Pressure,
which brings in wet, warm air
off the Pacific Ocean
(the “Pineapple Express”)
https://www.youtube.com/watch?v=V3I6PBwU5fQ
Floating Bridges, Waves, and Weather
• Floating bridges dampen waves,
so water on the downwind side
will be calm, water on the
upwind side will be choppy
• Waves will be bigger on the
north side of I-90 when there is
high pressure (wind from the
north) = _______ weather
• Waves will be bigger on the
south side of I-90 when there is
low pressure (wind from the
south) = ______ weather
S
N
S
N
Floating Bridges, Waves, and Weather
• If you see sunny skies, but waves on the south side of I90 or 520, it means bad weather is moving in
S
N
Mini-Review:
• Winds blow towards _____ pressure,
where air ________________
H2O, which ______________
• The higher the gradient, the
higher the ____________
• Winds ________ due to the Coriolis
Effect
Winds will “follow” isobars due to Coriolis Effect
Climate:
Predominate weather patterns
Where are most rainforests and deserts
located and why?
Convection Currents
The pattern of a fluid
rising and then sinking due
to heating and cooling is
called a _______________.
Convection cells, combined
with the Coriolis Effect, drive
major _____ patterns on Earth
Convection Currents and Global
Wind Patterns
• Convection cells
mix air in the
troposphere &
transport ______ &
________ from one
area to another.
• Relative humidity
increases as the air
______ (right side) &
decreases as it
_____ (left side).
Fig. 7–5
Global Air Flow: Convection Cells
•Huge convection
cells of air
movement result in
global patterns of
low & high
pressure:
•_____ pressure
near 0º latitude
(tropics), leads to
high ________ as
warm, moisture–
laden air rises
•_____ pressure at
30º N & S latitudes,
results in deserts as
____ air descends;
Fig. 7–6
This convection cell between
the equator and 30° N or S is
called a Hadley cell
• Most rainforests are located at the
equator or at 60oN (or S).
•Since the equator receives the most
direct light, it heats up the most.
•As air heats up it expands and
rises (______ pressure Zone).
•As the air rises, it cools in the
upper troposphere and can
no longer hold as much
____________.
• This excess water vapor rains
down on the tropical region.
Most deserts are located at
30° N or 30° S.
• Air from the equator, moves
towards the poles, _______
and descends back towards
the Earth at these latitudes.
• This air is ____ because it lost
its moisture at the equator
• As it descends, it warms so it
has a greater water vapor
capacity. _______________
(% of moisture relative to its
maximum) decreases.
• This causes very little __________
60oN
At 60oN and 60oS, convection
cells create ____________ air,
producing a ______climate. The
climate is cold due to the high
latitudes
What about the Poles?
• Air is ________so the relative
humidity will be ______, and the air
will be ______ (it is also so cold that
it cannot hold much moisture.
• The poles are sometimes called
Polar __________
• Most precipitation is at the equator, since the warm temperatures
will lead to the most________________
Discuss with your table partner:
These Hadley Cells are not fixed right at the
equator- they are centered at the location that
receives the most direct heating, which drives the
process. The area between the two Hadley Cells is
called the Intertropical Convergence Zone (ITCZ)
Predict in which season(s):
The ITCZ is located at the equator.
The ITCZ is to the North of the equator.
The ITCZ is to the South of the equator
http://www.youtube.com/watch?v=T6Us1sPXBfA
The drier seasons at the equator occur when
the ITCZ is shifted __________ from it.
Since the Hadley Cells are centered around the
equator for the majority of the year, the diagrams
will show it as centered at the equator.
Global Wind Patterns
The convection cell
patterns and the Coriolis
effect interact to create
general global wind
patterns.
Winds are named based on
the direction of their
_________, and reflect wind
direction at Earth’s ________
(not at high altitudes).
Westerlies= From the ______
Discuss with your table partner:
Review the Hadley Cell between the equator (O°) and 30°
N. At the ground level does wind blow from North to
South or South to North?
Hint: Where is the low pressure? (Air moves towards
low pressure).
Review which direction does the Coriolis Effect deflects
wind in the Northern and Southern Hemispheres.
On the next slide, draw these directions as vector lines
and combine them to determine the direction of the
wind in this zone. Then repeat the process for the 30 S to
equator zone and the 30 N to 60 N zones on the following
slides.
Direction of the Coriolis Force in the Northern
Hemisphere: ____________
Be sure to draw the right or left arrow from the
perspective of the North/South arrow.
30° N ______ Pressure
Due to sinking air in
Hadley cell.
0° (equator) ____ Pressure
Due to rising air in
Hadley cell.
Direction of the Coriolis Force in the Southern
Hemisphere _____________________
Be sure to draw the right or left arrow from the
perspective of the North/South arrow.
0° (equator) _____ Pressure
30° S ______ Pressure
Direction of the Coriolis Force in the Northern
Hemisphere _____________________
Be sure to draw the right or left arrow from the
perspective of the North/South arrow.
60° N ________ Pressure
30° N _______ Pressure
Due to sinking air in
Hadley cell.
Global Wind Patterns
The Coriolis Effect deflects __________ winds to the right in
the Northern Hemisphere, and to the left in the S. Hemisphere,
causing the prevailing winds. Winds are named based on the
direction of their origin:
Doldrums (fairly still air)
along the equator)
Tradewinds blow from
the east (0-30N and S)
Westerlies: blow from
the west (30-60oN and
S),
Easterlies: blow from
the east 60-90oN and S)
Fig. 7–4
Trade winds or Easterlies: equator (0 °) to 30° N and S
• Air returns across the surface of the earth to the
_____ pressure zone at the equator (Hadley cell)
• It is deflected to the _________ in the Northern
hemisphere.
• Moving N to S, right deflection= towards the west.
• NE trade winds between equator and 30° N (to SW)
30° N
0°
• In Southern Hemisphere, the air is deflected to ____.
• Moving S to N, left deflection = towards the _______
• SE trade winds between equator and 30° S (to NW)
Westerlies: 30°- 60° (both N & S),
• Air moves from high pressure zone at 30° N
___________ the poles.
• Air moving ___________ the poles goes towards
the east (westerly winds)
•http://www.youtube.com/watch?v=ieILUnkdD90
Microclimate
Local climate conditions due to factors such as topography or water
bodies are known as microclimate.
For example, as air moves over a mountain range it _________ as it
rises. The cooler air can not hold as much moisture, resulting in
________ on the ____________ side.
The leeward side (downwind) of the mountain range is ____________
because the air temperature rises as it moves to lower elevations.
The leeward side of a mountain range is called the ______________.
Small Rain
Shadow
Rain Shadow
Prevailing
winds
during wet
weather
(from SW)
Discuss with your table partner:
Explain why the west coast of Peru is mostly a
desert biome. (Hint: what is the latitude of Peru? )
Air flows _________ from
the Equator and gets
deflected to the ______
(_____).
These are ________ winds,
known as the ________
winds.
The east side of the Andes is _______ and the west
side is _______ between 0° and 30° S.