more climatic interactions ms. clark. winds the movement of air in a horizontal direction what is...
TRANSCRIPT
More Climatic Interactions
Ms. Clark
The movement of air in a horizontal direction
What is wind?
The uneven heating of the Earth causes differences in air pressure.
What causes wind?
The Sun’s energy is more concentrated at the Equator and spread out more over the poles.
Air over the equator is warm and less dense and has lower pressure.
Air over the poles is cold and denser and has higher pressure.
Why does this happen?
As warm air at the equator rises, cooler air from the poles will move in and replace it.
Air pressure moves in a pattern from high to low.
Why does this happen?
As warm air at the equator rises, cooler air from the poles will move in and replace it.
Convection
The density changes caused by temperature changes create convection cells.
These cause circular patterns of air that circulate over the whole planet.
Global Convection Currents
Where the convections cells meet, prevailing winds and jet streams form.
They blow from one direction over a certain area of the Earth’s surface.
Global Wind Belts
Jet Stream
Forms high in the upper Troposphere between two air masses of different temperatures
Higher temperature difference = faster speed Due to the Coriolis Effect, it flows around air
masses. Polar Jet:
It dips southward when frigid polar air masses move south.
It tends to stay north in the summer months.
Jet Stream Animation
http://www.pbs.org/wgbh/nova/vanished/jetstr_five.html
Named for the direction from which they blow: Polar Easterlies – High latitudes blow east to
west toward the equator Westerlies – Mid latitudes blow west to east
toward the poles Easterlies (Trade Winds) – Low latitudes
blow east to west toward the Equator
Prevailing Winds
Prevailing Winds
Pressure belts form in between the wind belts.
Prevailing Winds
0 o Equator 30 o S 60 o S 90 o S30 o N60 o N90 o N
MoreDirect Sun Hot
The winds from the poles blow toward the equator.
The winds from the equator blow toward the poles.
Global Wind Belts
…then why is it defined as the horizontal movement of air?
*Reflection Question*Does the Earth stand still?
If wind is moving north and south, …
As the Earth rotates counterclockwise, the winds bend and curve around the Earth.
Gustave-Gaspard Coriolis, an engineer and mathematician, described this effect as an inertial force in 1835.
The Coriolis Effect
In the Northern Hemisphere, winds bend to the right of their direction of travel.
In the Southern Hemisphere, winds bend to the left of their direction of travel.
Let’s try a little investigation to see how this works.
The Coriolis Effect
Weather patterns and systems move in a circular motion due to the bending of the winds caused by the Earth’s rotation.
The Coriolis Effect
Our Earth is always seeking balance.
In an effort to find balance, there is a continuous cycle of patterns.
Reflection Question*What is the driving force behind the changes that create these patterns?
Equilibrium
Warm currents flow away from the equator.
Cold currents flow toward the equator.
Ocean Currents
SunWindCoriolisGravity
Factors Influencing Currents
Energy from the Sun heats the water. Warm water is less dense that cold water.
Warm water rises, and cold water sinks.
As warm water rises, cold water moves it to replace it.
Sun
Just as wind moves from high pressure to low pressure areas, so does the water.
Winds blow across the surface of the water, causing friction.
The water piles up because the surface currents flow slower than the winds.
Wind
As water piles up and flows from high pressure to low pressure, gravity will pull down on the water.
This forms vertical columns or mounds of water.
The Coriolis Effect causes the water to curve.
Gravity
Causes water to move to the right in the Northern Hemisphere
Causes water to move to the left in the Southern Hemisphere
The Coriolis Effect
Make up 10% of oceans’ water Up to maximum depth of 400 m Surface ocean currents are caused by the surface wind patterns.
Surface Currents
Vertical columns or mounds of water at the surface and flow around them
Produce enormous circular currents Five major locations:
North Pacific - clockwise South Pacific - counterclockwise Indian Ocean - counterclockwise South Atlantic - counterclockwise North Atlantic - clockwise
Gyres
A strong surface current Begins at the tip of Florida Flows up the eastern coastline of the
U.S. Crosses the Atlantic Ocean Causes warmer climate in NW Europe
Gulf Stream
Surface waters blow to the right of the wind.
As less dense, surface water moves off shore, cold, deep, denser waters come to the surface to replace them.
Upwelling
The Great Ocean Conveyor:Helps maintain Earth’s Balance
Make up about 90% of oceans’ water Differences in density cause them to move. Differences in density are related to
temperature and salinity. At high latitudes, they sink deep into the
ocean basins. Temperatures are so cold, they cause the
density to increase.
Deep Water Currents
How are ocean currents produced?
Reflective Question
Abnormally high surface ocean temperatures off the coast of South America
Causes unusual weather patterns across
the globe
El Nino
Starts because the easterly trade winds weaken and allow the warm waters in the Western Pacific to move east toward South America
This changes where the convection current occurs.
Causing rain where it usually doesn't occur and drought where it usually rains
El Nino
Abnormally low surface ocean temperatures off the coast of South America
Causes unusual weather patterns across
the globe
La Nina
Ocean currents move more slowly than winds. Oceans hold more heat than the atmosphere and
land. Cold currents will cause nearby coastlines to be
cooler. Warm currents will cause nearby coastlines to be
warmer.
Where do the cold currents come from? The warm currents?
Ocean’s Effect on Climate
Predictable Patterns How do these currents affect the climate
of the coastline?
How do our oceans impact climate?
Reflection Questions