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GEOS 212: EXAM 2
Zones in the ocean |
• Photic Zone (Sunlight, 0-100m)
• Twilight Zone (Poorly lit, no photosynthesis, <1000m) • Dark Zone (No light)
|
Sunlight does 4 things |
• Warms the ocean (Direct vs. Indirect sunlight)
• Reflects out (Red light is ABSORBED,
• Blue light is TRANSMITTED or REFLECTED.
• No red light below 10m (Red fish appears gray!)
• Drives Photosynthesis
• Drives Evaporation & Hydrologic Cycle
• Energy of Evaporation/Condensation vs Warming 540 cal/gram vs 1 cal/gram per degree)
|
Sunlight |
1. Warms Ocean 2. Reflects out
3. Photosynthesis 4. Evaporation
|
Evaporation |
Evaporation requires huge Sun energy Warming 1oC = 1 calorie/gram Evaporation = absorbs 540 calories/gram Condensation = releases 540 calories/gram
|
ATMOSPHERE:
MAIN GASES |
• ~10 km thick TROPOSPHERE (where weather happens)
• Nitrogen
• Oxygen
• Carbon Dioxide • Water vapor
|
Dry Atmospheric Composition |
N2
O2
CO2
Nitrogen (N2) = 78%
Oxygen (O2) = 21%
Argon (Ar) = 1%
Carbon Dioxide (CO2) = 0.0401%
(was 0.035% in 1988) (was 0.032% in 1965)
Plus
Water Vapor = 0% - 4%
|
Water vapor in atmosphere |
MAX =
3% if warm, 2% if cool, 1% if cold
|
Humidity = |
Amount of water present / Max amount air can hold
|
Humidity depends on temperature |
Cold: 1% / 1% = 100% humidity cloud/rain
Cool: 1% / 2% = 50% humidity
Warm: 1% / 3% = 33% humidity evaporation
|
Evaporation |
Liquid to Vapor
Energy IN
|
Condensation |
Vapor to Liquid
Energy OUT
|
Water transports energy by |
Evaporation & condensation
|
Wind = |
Sun energy converted to motion by air & water vapor
|
Energy = |
Lightning and Thunder
|
Coriolis Force |
Objects deflect light to the right in the northern hemisphere
Objects deflect light to the left in the southern hemisphere
|
Rising air has |
increasing humidity and eventually RAIN
|
Descending air has |
decreasing humidity = DRYING
|
Winds generally blow from |
high pressure toward low pressure
|
Low pressure is rising air = |
rain
|
High pressure is descending air = |
dry
|
Energy out during precipitation |
540 cal/gm OUT (released to air)
|
Energy in during evaporation |
540 cal/gm IN (from sun)
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Sun energy can drive |
BIG WINDS!
|
Hurricane: max wind |
> 150mph
|
Tornado: max wind |
> 250mph
|
Wind drives = |
Surface currents
|
Surface currents = |
Surface currents = Gyres
|
Winds push warm water west, cold water east |
matters for El Niño
|
Process by which surface currents transport heat: |
1. Sun warms water near equator
2. Wind belts drive currents
3. Currents run into continents and turn
4. Warm water carried poleward and releases heat
|
Fully-Developed Sea |
The maximum ocean waves that can be produced by a wind if it is blowing over sufficient fetch for sufficient duration.
|
The strongest winds are found: |
In the Westerlies
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As the wind speed increases, the wave height: |
Increases slowly at first and then more rapidly
|
Fetch is: |
The area over which the wind is blowing
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Conditions above the FDS curve are good for: |
Surfing
|
The Southern Ocean has the biggest waves because it has: |
1. Infinite fetch
2. Really big storms that last for days
3. The strongest winds
|
Ice |
Winter = Growing Summer = Melting
|
Salinity |
Winter = Salty Summer = Fresh
|
El Niño |
- a coupled phenomenon of the Tropical Pacific
- needs both atmosphere and ocean
|
NORMAL
1. Moderate easterlies
2. Warm ocean in west
3. Cool ocean in east
4. Rain in west (Indo/Aus)
5. Dry in east (Peru) |
EL NIÑO
1. Weak easterlies
2. Warm ocean in east
3. Rain follows the heat
4. Dry in west (Indo/Aus)
5. Wet in east (Peru)
|
EL NIÑO
1. Weak easterlies
2. Warm ocean in east
3. Rain follows the heat
4. Dry in west (Indo/Aus)
5. Wet in east (Peru) |
LA NIÑA
1. Stronger easterlies
2. Colder ocean in east
3. Rain follows the heat
4. Extra wet in west (Indo/Aus)
5. Extra dry in east (Peru)
|
Hurricane Wilma = |
lowest pressure EVER in Atlantic
|
Normal = |
1000mb, Wilma was 888mb winds ~160mph
|
Katrina - N. Hemisphere = |
Spins Counterclockwise
|
Yasi - S. Hemisphere = |
Spins Clockwise
|
Hurricanes |
1. Forms as a low pressure system
2. Grows/organizes over warm water (>79°F) into a "tropical depression"
3. When winds exceed 39mph, it gets a name and is called a "tropical storm"
4. When winds exceed 74mph it becomes a hurricane
5. Weakens over land and/or cold water
|
Storm Surge |
- A mound of seawater under the Hurricane eye.
- Can exceed 20 feet in height.
- New Orleans is particularly vulnerable.
|
TSUNAMI ("harbor wave") |
Wavelength = 200 km (wave base = 100km >> water depth)
In Deep water:
500 mph in deep water
1-3 foot tall
In Shallow water: 30 mph
can be >100 ft tall
|
TSUNAMI Warning System |
DART Buoys
|
Why are Tsunami so hazardous? |
1) Travel fast
2) Hard to see in deep water
3) Build to large height on shore
4) Many waves - and first one may be low or a trough!
5) No warning if earthquake far away
6) Affect huge area of coastline
7) Rare - so people forget!
|
Tides |
• Wave (up to 20 ft change!)
• Two Hi & two Lo per day
• East & west sides of ocean are opposite
• Tide range changes during month
|
Tide amplitude varies over 28 days because it's driven by gravitational pull of the moon and sun |
1) Gravitational pull from the moon makes high tide (strongest because closest)
2) High tide modulated by position of the sun
3) Because the Earth is elastic, creates bulge on both sides of earth,
so 2 high and 2 low tides per day
4) When sun and moon work together: big tidal range = spring tides 5) When sun and moon work against each other:
small tidal range = neap tides
So every 28 days, two spring and two neap tides
|
Why are Tsunami so hazardous? |
1) Travel fast (500 mph)
2) Hard to see in deep water (1-3ft, huge wavelength)
3) Build to large height on shore
4) Many waves -
5) First one often a low - not as tall or water goes OUT first!
6) No warning if earthquake far away
7) Affect huge area of coastline (like all of Pacific margin!)
8) Rare - so people forget!
|