Bio 126 Climate and Weather

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Bio 126Climate and Weather
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Earth from the moon
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Meteorology

• Climate- over all combination of temperature and
  precipitation that a region experiences
• Mediterranean winter precipitation followed by
  long hot, dry summers
• Weather- daily, weekly variations in these
  phenomena

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Solar radiation
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Climate zones

• Warm at equator, cooler towards poles.
• Caused by intensity of sunlight at equator.
• Poles receive less on a per area basis.

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Solar radiation around the Globe
Solar radiation around the Globe
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Seasons

• Caused by tilting of earth on its rotational
  axis.
• Intensity of sunlight varies.
• Most extreme at poles
• Little change at equator.

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Causes of Seasons
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Precipitation

• Varies by latitude.
• Wet at equator 00, and 600 N / S
• Dry at 300, and 900 poles
• Poles are frozen deserts
• Caused by formation of Hadley Cells

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Hadley Cells

• Air currents in Hadley Cells caused by air
  density not just temperature.
• Uneven heating in different regions on the earth
  cause winds.

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Hadley Cells

• Air rises (0, 60) due to warming of surface.
• Adiabatic Cooling as air rises
• as rises the air becomes less dense and cooler
• this cause water to condense and fall as rain,
  snow
• Air falls (30, poles)
• Adiabatic warming as air falls
• air becomes compressed, and heats.
• air absorbs moisture, falls as dry air and
  absorbs moisture from the environment.

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Global air circulation, precipitation, and winds
Hadley cells
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Global Air Circulation
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West Coast Latitudes

• San Diego32.5 LA 34 Sta. Barbara 34.5
  Sta. Cruz37, SF 37.75 Eureka 40.75
• Approx. Portland 45.5 Seattle 47.5 Juneau
  58 Anchorage 61
• CA large enough to span climate zones between
  Hadley cells.
• South dry
• North wet

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Seasons-

• tilting of earth moves solar equator.
• Effectively moves 300 dry zone north in summer
• descending dry air belt is pushed farther north
  in our summer,
• the wet belt moves farther south giving us wet
  winters

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Causes of Seasons
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Prevailing winds

• These Hadley cell wind currents move North or
  South
• The spinning of the earth makes it seem like they
  come at an angle.
• In CA our winds, storms usually come from the
  south west.
• Rains often bring warmer weather

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Ocean currents

• Prevailing winds cause ocean waters to move in
  the prevailing direction.
• huge gyres form due to earths spinning known as
  the Coriolus effect
• In Northern Pacific clockwise general direction
  of flow from our coast.
• Ca. Current, with its cold, nutrient rich water
  flows from Alaska southwards along our coast
• At Sta. Barbara coastline moves east, current
  flows due south, allowing Southern Ca. water to
  warm

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Hadley cells
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Barometer measures air pressure

• Low pressure (rising air) associated with storms.
  
• High pressure (descending air) blocks storms.
• High pressure off California in summer blocks
  most storms

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Global Trade Wind Patterns
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Ocean Currents
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Biomes

• Major vegetation types that also determine the
  animal community present.
• Determined mostly by climate
• Soil also important factor

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Figure 50.3 A climograph for some major kinds of
ecosystems (biomes) in North America
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Biomes
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Patterns of distribution in the biosphere
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Major Biomes
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Coniferous forest, Lady Bird Grove (top left),
Sequoias (right), rain forest (bottom left)
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Temperate deciduous forest, Great Smokey
Mountains National Park
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Tropical forests
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Savanna
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Desert. Organ Pipe State Park (top), Joshua Tree
National Park (bottom left), Death Valley
(bottom right)
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Temperate grassland- Prairie
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Tundra. Denali National Park (left), reindeer
(right)
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Rain shadow

• Precipitation increases as storms are pushed up
  over mountians.
• accordingly rain becomes snow
• As air moves up slope in the Sierras it cools 3-5
  degrees per 1,000 ft.
• This is the same effect as moving 300 miles
  farther north !
• Causes deserts in Nevada
• Most islands with mountains have wet and dry
  sides

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Rainshadow
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Rainshadow
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Summer Fog

• Inland air warms quickly. This rising air, pulls
  in coastal air.
• Cold water off CA. cools incoming warm, moist
  ocean
• Coast causes summer fog.
• Essential for southern ranges of Coast Redwoods,
  and relic pines, cypress species

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Temperature Inversion layers

• dense air flows downhill and collects in low
  spots, valleys. Great Central valley is an
  example.
• This dense air may be blocked by hills etc. from
  warmer winds which blow over the top of dense
  air, leaving it alone.
• Dense tule fog may form for days.
• Inversion layer (cold air higher up) also traps
  pollutants.
• Mexico City problems
• Reno, Tahoe now ban fireplaces.
• Often burn off in summer but leave the haze of
  phytochemical smog behind.

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