Download Bio 126 Climate and Weather

Bio 126
Climate and Weather
Earth from the moon
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
Solar radiation
Climate zones

Warm at equator, cooler towards
poles.
– Caused by intensity of sunlight at
equator.
– Poles receive less on a per area basis.
Solar radiation around the Globe
Solar radiation around the Globe
Seasons

Caused by tilting of earth on its
rotational axis.
– Intensity of sunlight varies.
– Most extreme at poles
– Little change at equator.
Causes of Seasons
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
Hadley Cells

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Air currents in Hadley Cells caused
by air density not just temperature.
Uneven heating in different regions
on the earth cause winds.
Hadley Cells

Air rises (0, 60) due to warming of
surface.
–
Adiabatic Cooling as air rises

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
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.
Global air circulation, precipitation, and winds: Hadley cells
Global Air Circulation
West Coast Latitudes

San Diego=32.5; LA= 34; Sta. Barbara=
34.5 ; Sta. Cruz=37, 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.

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–
–
South dry
North wet
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
Causes of Seasons
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
Ocean currents


Prevailing winds cause ocean waters to
move in the prevailing direction.
huge gyres form due to earth’s 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
Hadley cells
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
Global Trade Wind Patterns
Ocean Currents
Biomes
Major vegetation types that also
determine the animal community
present.
 Determined mostly by climate

– Soil also important factor
Figure 50.3 A climograph for some major kinds of ecosystems (biomes) in
North America
Biomes
Patterns of distribution in the biosphere
Major Biomes
Coniferous forest, Lady Bird Grove (top left), Sequoias (right), rain forest
(bottom left)
Temperate deciduous forest, Great Smokey Mountains National Park
Tropical forests
Savanna
Desert. Organ Pipe State Park (top), Joshua Tree National Park (bottom left), Death
Valley (bottom right)
Temperate grassland- Prairie
Tundra. Denali National Park (left), reindeer (right)
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.

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This is the same effect as moving 300
miles farther north !
Causes deserts in Nevada
Most islands with mountains have
wet and dry sides
Rainshadow
Rainshadow
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
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.

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Mexico City problems
Reno, Tahoe now ban fireplaces.
Often “burn off” in summer but leave the haze
of phytochemical smog behind.