Transcript Ocean Circulation

Warmup Wednesday 9/30
1) As you go up into the atmosphere, is it
hotter or colder (in general)
2) Does the air around us have a weight?
EXTRA: What is a “barometer?”… anybody
know?
Key Concepts today
1. Convection
2. Low & High pressure in the
atmosphere
3. Hurricane formation
4. Classification and power of
hurricanes
Basic “convection”
• Heat goes up, cold goes down…
• Increasing heat makes things expand,
makes density less and thus it rises if it
can
• Taking away heat makes things contract,
thus MORE dense and sink
Hurricanes – the largest &
strongest storms on this planet!
How do they form?
First – you need to understand how
convection works, and
Then a little more about high pressure
and low pressure in the atmosphere.
And then we can tackle how a hurricane
forms
The air on us has “pressure”… why
don’t we feel it?
Barometers measure air pressure
• Original barometers used
Mercury – how much
mercury would the air
hold up in a vacuum
tube
• Modern barometers use
an enclosed cell that
expands or contracts and
moves a lever
Low and High pressure
Air tries to move from
________ to __________
How does a “low pressure” form?
CONVECTION!!!!!!!!!! As
the air is heated,
rises…. Leaving a “hole”
Air will be pulled in to
replace it
HOT
Equator
warm
warm
As warm humid air rises, it cools and the water
vapor eventually will condense back into water to
form a cloud and eventually rain
RELEASING LOTS OF ENERGY AS IT DOES
Low pressure sucks, highs blow
• If hot air rising creates “low” pressure,
What might cause a “high” pressure?
So, the center of a hurricane is a “super
low” , sucking in all the hot humid air
around it… but
Why do hurricanes to spin counterclockwise
Warmup: 10/1 Thursday
1) Over long distances, moving things in
the atmosphere will turn to the
________ in the northern hemisphere
2) The force that causes them to turn is the
__________ effect
3) ________________ causes an area of
low pressure.
Anything in the north
hemisphere moving will turn to
the right! (Coriolis effect)
South:Left
North:right
Pause, then back to hurricanes:
Lets detail “Coriolis”
Coreolis is simple… yet very very confusing
1) Because we are on a spinning ball, even
something going straight appears to
curve over a long distance
2) This effect gets magnified by everything
else turning!
(no, this has nothing to do with toilet water spinning and no toilets
don’t spin the other way in the southern hemisphere)
The Coriolis Effect
An object moving across a rotating
surface keeps the same direction
and speed, but looks seems it
curves if you are on the rotating
surface.
In the fixed frame of reference,
the black ball moves in a straight
line.
However, the observer (red dot)
standing in the rotating frame of
reference sees the object as
following a curved path.
http://en.wikipedia.org/wiki/Image:Corioliskraftanimation.gif
This turning to the right, causes
hurricanes to spiral counter
clockwise in the north
• In the
southern
hemisphere
they spin
clockwise
Hurricanes really “suck”
Base of the eye is a hot area of low pressure
Surrounding warm humid air moves toward the low, spiraling,
getting warmer and rising up, losing moisture
Anatomy of a hurricane
Winds are breezy at the edge of the storm and increase to a maximum in
the eyewall. Winds are relatively light in the ‘eye’ itself.
Or another view
OK, so far
1) Still hot humid air rises (Convection) causing
2)
3)
low pressure “hole”
Air moving in to fill the low will turn to the
right & it is FULL OF WATER VAPOR!!!!!!!
Air spirals and rises, ALL THE WATER
CONDENSES – FORMING HUGE THICK
CLOUDS & RELEASING LOTS OF ENERGY
If the “low” is just temporary and
small.. = thunderstorm
1) Still hot humid air rises (Convection) causing
2)
3)
low pressure “hole”
Air moving in to fill the low will turn to the
right & it is FULL OF WATER VAPOR!!!!!!!
Air spirals and rises, ALL THE WATER
CONDENSES – FORMING HUGE THICK
CLOUDS & RELEASING LOTS OF ENERGY
If the “low” is long lasting, very hot
and a large area…. = Cyclone!
1) Still hot humid air rises (Convection) causing
2)
3)
low pressure “hole”
Air moving in to fill the low will turn to the
right & it is FULL OF WATER VAPOR!!!!!!!
Air spirals and rises, ALL THE WATER
CONDENSES – FORMING HUGE THICK
CLOUDS & RELEASING LOTS OF ENERGY
Tropical Cyclones go by different
names… (why do they all go west?
Ingredients for a hurricane:
• Ocean is very warm and the warm is deep (80
•
•
•
•
degrees down to 150ft)
Everything is calm (low winds), so air heats up
Air rises quickly and creates a “super low”
pressure area
HOT, humid, water carrying air zooms into the
“super low” pressure carrying crazy amounts of
water and heat energy into the storm
As it spirals up the eye it loses all it moisture
and we get massive condensation (rain clouds)!
Storm Surge – the most deadly
part of the hurricane!!!!!
The “LOW” pressure sucks in more than just
air. It actually pulls the ocean surface up!
Add this to the huge waves caused by wind…
Categories Pressure
(normal
ly above
1000)
Tropical
>993
storm
H1
>993
Winds
mph
Storm
surge
ft
Damage ….
<74
1-3
Flood large areas
74-95
4-5
Take out trees
H2
979-965
96-110
6-8
Rip roof off
H3
964-945
111-130 9-12
Knock small
buildings
down
H4
944-920
131-155 13-18
Destroy even
large buildings
H5
<920
155+
Extreme damage
19+
Before and after pictures