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Chapter 7: The Ocean and Atmosphere
• Objectives:• Structure/composition of air
• Sulfur compounds
• General circulation patterns
• Coriolis Effect
• Seasonal Changes
• El Nino, La Nina
• Storms
• Practical Considerations
Ocean and Atmosphere
• Can’t separate; closely related:
• Moderates surface temperature
• Shapes weather and climate
• Creates most of sea’s waves and currents
Structure and Composition• 90% of gases = within 9 mi. from surface
• Troposphere temp. from conduction
• Greenhouse Effect; Global Warming
• Stratosphere: Ozone; depletion
• Mesosphere: colder
• Thermosphere: leads to outer space
• 78% N, 21% O in dry air
• Weather =
• Climate =
• Influenced by:
Solar radiation
Land
Nearby body of water
Changing geo and bio conditions
Measuring Earthshine How much radiation the Earth reflects.
GREENHOUSE EFFECT• Gases: CO2, CH4, H2O, CFC, N2O
• Trend: increase in gases global warming of 2-4 degrees C in next 100 yrs.
• **Unbalances C cycle• Possible sea-surface effects:
– Affects high latitudes melt polar icecaps
– Affects thermohaline circulation and surface winds modify transfer of heat from low to high latitudes alters Earth’s climate patterns
OZONE DEPLETION• Monitored since 1978• CFC’s (1 molecule breaks down 100,000 molecules of
ozone)• Methyl bromide: from single celled algae at surface,
pesticides, industry, burning of vegetation.• Problems:• Pollutant at ground level• Skin cancer, cataracts• Sunburns, earlier wrinkles• Suppress immune systems crop production• Degradation of paint, plastics in phytoplankton productivity
Ozone Depletion
Sulfur Compounds• 20-40 million T from dimethyl sulfide
(DMS) from phytoplankton at surface (odor of sea)
• DMS sulfate & water sulfuric acid acid rain
• Controls density of clouds over sea
• DMS changes reflective prop., reduces incoming radiation, heating of ocean surface
DMS, excess clouds + sulfur over sea less light hitting surface, temp , plant production of DMS
SELF REGULATING
ATMOSPHERIC CIRCULATION• Uneven solar heating wind
• Convection current
• Patterns if world was still
• CORIOLIS EFFECT: apparent deflection of a moving object from its initial course when its speed and direction = measured in reference to the surface of the rotating Earth.
• Earth moves 15 degrees/hour
• All places on Earth don’t move at same speed
• N. Hemisphere winds = clockwise
• S. Hemisphere counterclockwise
• Equator none
• Coriolis Effect only influences wind
Wind Bands• Geographical Equator = 0o
• Meteorological Equator = ITCZ, ~5o N or S of Equator
*Maintains thermal equilibrium
• 3 convection cells of air:
1. 0o--30o
2. 30o--60o
3. 60o--90o
Wind Patterns1. Trade winds: bands of moving air
between 0--30
movement to right (west)
steady speed, direction
2. Westerlies: between 30--60
go to east
Winds = named for direction of origin
3. Horse Latitudes: 30 degrees N and S
air = dry, deserts
4. Doldrums: at Equator
low a.p., moist air, rainforests
vertical movement of air
5. Polar Easterlies: betw. 60 degrees and
and the Poles
6 surface wind bands
Measuring winds: surface, satellites
• Cell circulation: depends on
1. Seasonal changes
2. Amount of land
3. Amount of ocean
**Remember: land doesn’t have the high heat capacity of water --> temperature fluctuations = greater.
Seabreeze
Landbreeze
MONSOONS• Pattern of wind circulation that changes
with seasons due to heat capacities of land and water and moving ITCZ.
• Wet summers, dry winters
• In spring: land heats more rapidly than ocean, air over land rises and cool moist air rushes in to take its place --> rain
• In winter: opposite. Dry surface winds move seaward.
Delhi Floods
Air Masses• Large body of air with nearly same temp,
humidity, and density throughout
• characteristics come from where they were formed
• mT (maritime tropical) = warm, moist
• mP (maritime polar) = cold, moist
• cT (continental tropical) = warm, dry
• cP (continental polar) = cold, dry
• cold front, warm front, stationary front
• Storms: Regional atmospheric disturbances characterized by strong winds and precipitation.
• Cyclones: huge rotating masses of low pressure in which winds converge and ascend.
Extratropical Cyclone• Form between each hemisphere’s polar
and Ferrell cells
• occur in winter
• from 1000-2500 km in diameter (625-1600 mi.)
• In North America = nor’easters
• Example: “Perfect Storm”
Perfect Storm
The storm—created from a collision between a high
pressure system, a low pressure system and the
remnants from a dying hurricane—sent high winds and
Atlantic Ocean waves crashing into the East Coast, from
New England to Cape Hatteras, North Carolina.
The Perfect Storm
Tropical Cyclones• Great masses of warm, humid rotating air
• Hurricanes in Atlantic
• Typhoons in Pacific
• Tropical Cyclones in Indian Ocean
• Willi-willis in Australia
• less force = tropical depression --> tropical storm
• Hurricane status = 74 mph
• = most powerful storm on earth
• 20 billion metric T of water/day
• Danger: storm surge
high winds
rain
• Eye: calm, wind shifts direction
• On land, weakens due to surface friction, no power source.
1813-189-126-84-5Surge
(feet)
CatastrophicExtremeExtensiveModerateMinimalDamage
155131-155111-13096-11074-95Wind
(mph)
919944-920964-945979-965 980Pressure
(mb)
54321Category
The Saffir-Simpson Scale
Squall• Sudden increase in wind speed by 16 knots,
rising to 22 knots or more and lasting for at least 1 minute---then diminishes.
• Associated with cold fronts• sharp drop in temp.• roll shaped cloud• rain shower• may be snow
Florida, U.S.A Squall Line
Target Name: Earth
Spacecraft: Space Shuttle
Produced by: NASA
Copyright: NASA Copyright Free Policy
Cross Reference: STS41C-40-2130
Date Released: April 1984
Practical Considerations• Preventions:
evacuations
dikes
gate in Thames
other precautions?
Decision: prevention or cleanup?
Should historically proned areas be vacated?
Hurricane Katrina
Hurricane Ivan
Hurricane Frances
September 2004
Hugo
Hugo
Hugo
Hurricane Ivan
Ivan