WINDS

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WINDS

• LOCAL, REGIONAL AND GLOBAL SCALE WINDS,
• EL NIÑO AND SOUTHERN OSCILLATION (ENSO)

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LOCAL SCALE WINDS

• Sea Breeze-Land Breeze Circulation
• Due to temperature differences between coastal
  and inland regions
• For southern California, the most likely time for
  Sea-Breeze is Summer, late afternoon
• Warmer regions inland set up conditions to build
  thermal low air pressure
• Cooler water along coastal regions sets up
  conditions to build thermal high air pressure
• Air always moves from areas of higher pressure to
  areas of lower pressure.

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Sea Breeze Circulation
Afternoon warming of valley floors, produces
thermals of warm rising air Thermal Low
develops over valleys. Over the ocean, cooler
water produces a Thermal High with cool sinking
air. Result Cool, moist air flows onshore
toward valleys in late afternoons. Effects
Decrease in temperature and an increase in
relative humidity. Locally, sea breeze from
Santa Monica Bay flows onshore and makes its way
into the surrounding Los Angeles Basin, even into
the San Fernando Valley
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Land Breeze Circulation

• During night, radiational cooling in the local
  valleys lifts warmer air away from valley flo0rs
  creating an inversion layer in the atmosphere
• Valley regions are cooler at the surface
  producing a thermal high pressure.
• C0astal areas are slightly warmer than adjacent
  valleys, producing a thermal low pressure.
• Time for the greatest difference in temperatures
  is close to sunrise, setting up conditions for a
  land breeze, as air is moved offshore from
  valleys to coast.

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Land Breeze Circulation
Differences in temperature between adjacent
valleys and coastal area set up conditions for
offshore flow of air
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Mountain and Valley Breezes
Similar to the land and sea breeze in its diurnal
cycle are the valley and mountain breezes.
Valley breezes occur in the day because air
along mountain slopes is heated more intensely
than air at the same elevation over a valley
floor. Rapid radiational heat loss in the
evening reverses the process to produce a
mountain breeze.
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Santa Ana Winds

• Santa Ana Winds are warm, dry, high velocity
  winds that flow into southern California.
• The winds usually begin in late summer-early fall
  and extend to December typically ending with the
  arrival of the winter rainy season.
• The source region for the winds is northeast of
  southern California near Utah.
• In the late summer-early summer, a large high
  pressure system (The Great Basin High) develops
  near the area of Utah, western United States.

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Santa Ana Winds

• Average elevation in Utah is 5000 feet, while
  average elevation in southern California is 500
  feet a 4500 foot difference.
• Descending air is heated by compression (dry rate
  of heating at 100C/1000 meters or 5.50 F/1000
  feet).
• 250 F added to the air temperature as it descends
  from the high towards southern California
• Warmed air is funneled between Sierra Nevada on
  west and Wasatch Mountains to the East.
• Air flows over Mojave Desert lowering specific
  humidity.
• Acceleration of the air occurs two ways
• Funneling through the canyons of the Transverse
  Ranges
• Flowing downslope the Transverse Ranges under
  gravity

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Great Basin High forming near Utah, producing
conditions for development of Santa Ana Winds in
southern California. Note the isobaric pressure
near Utah, compared to southern
California. Temperatures near Utah are in the
mid-50s F, while temperatures in southern
California are in the high 80s F.
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Santa Ana Winds Hot, Dry and High Velocity
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Santa Ana Winds and Fire Season in southern
California
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Recent Fires in southern California
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CONTINENTAL SCALE WINDS MONSOONS

• Monsoon - from Arabic word mausim means
  changing wind directions with a change in
  season.
• Monsoon are associated with heavy precipitation.
• There are monsoons in many areas of the world,
  including western United States.
• Arizona, for example, receives most of its annual
  precipitation during its summer monsoonal season
• Most described are the monsoons in southern Asia
  India.
• India has two monsoons Winter and Summer

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Winter Monsoon in India

• During the winter, the Asian landmass becomes
  very cold, producing a large high pressure system
  over most of the southern Asian region.
• This high pressure rotates air clockwise, out
  from the center pushing the cool, relatively dry
  air off the subcontinent.
• The warmer waters of the Indian Ocean produce a
  relatively weak low pressure system.

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Winter Monsoon in India
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Summer Monsoons in India

• In summer, the Asian continental landmass heats
  up producing very large thermal Low air pressure
  systems
• Over the relatively cooler Indian Ocean, a
  thermal high pressure develops
• The large continental Low draws in the cool, high
  humidity air from the Indian Ocean.
• The cool humid air is lifted along the Himalayan
  Mountains, producing massive amounts of
  precipitation in the northern regions of India

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Summer Monsoons in India
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East Asian Monsoons
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Bangladesh
Summer Monsoon, India
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UPWELLING AND OCEAN CURRENTS

• Cold ocean currents flow almost parallel to the
  west coast of large continents
• California Current, North America
• Humboldt (Peru) Current, South America
• Benguela Current, Africa
• The Earth's rotation and strong seasonal winds
  push the surface water away from the western
  coast of North America, South America and
  Africa. 
• Upwelling of the nutrient rich water occurs on
  the western edge of the continental shelf
  replacing the warmer waters.
• The abundant marine life within the Galapagos
  Archipelago thrives in these nutrient rich waters.

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UPWELLING PROCESS
Peru
Humboldt Current
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Upwelling along west coast of South America
Humboldt Current flows north along west coast of
South America. Coriolis Force pulls the surface
water away from coastline, allowing upwelling of
nutrient-rich deep and cold water.
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El Niño

• El Niño originally referred to the warm ocean
  current that appears along the Pacific coast of
  South America each year around Christmas
• El Niño is an atmospheric and oceanic disturbance
  in the tropical Pacific Ocean.
• The name was given by Peruvian fishermen owing to
  the timing of the appearance of this disturbance.
• During an El Niño event the following events
  occur
• Dwindling of trade winds
• Changes in barometric pressure across the Pacific
• Sea surface temperature anomalies are recorded
• Rainfall patterns are disrupted

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El Niño and the Humboldt Current

• The Humboldt Current is a northward flowing
  current along the west side of South America
• Coriolis Force and surface winds act to pull
  surface water away from the coast creating
  Upwelling along the west coast of South America
• Upwelling promotes
• Plankton growth as they follow the cold water
  pulled up from depth
• Anchovies follow the plankton major food source
• Sea birds follow the anchovies
• Guano is deposited on local islands by the sea
  birds

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Normal Conditions in tropical Pacific
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El Niño in tropical Pacific
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El Niño and Peruvian Fishing Industry

• During an El Niño, the fishing industry in Peru
  experiences a strong decline
• Perus fishing industry accounts for a
  significant portion of Perus economy
• Worlds foremost producer and exporter of
  fishmeal
• Fishmeal a major component of all animal feed
  globally
• In historic El Niño events, cost of animal feed
  increased around the world due to the collapse of
  Peruvian fishing
• 1972-73 El Niño
• Anchovy catch reduced from 10.3 million metric
  tons (1971) to 4.6 million metric tons (1972)
• 1982-83 El Niño
• Anchovy catch reduced by 50 from 1981 catch

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El Niño and Upwelling
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El Niño-Southern Oscillation EventsWalker Cycle
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El Niño Southern Oscillation Events (ENSO)

• Upwelling along Peruvian coast ceases
• Trade winds weaken
• Weak equatorial eastward current develops
• Moisture and temperature patterns alter as air
  pressure systems flip-flop
• Normal high pressure near Peru moves toward
  western Pacific creating droughts in Australia
• Normal low pressure near mid-Pacific moves toward
  Peru, creating records storms, floods and
  landslides