Mother Earth is hospitable due to the greenhouse effect.
∙ Earth’s atmosphere is: 78%
N2, 21% O2 and 1% other gases.
∙ Other gases include CO2,
methane, nitrogen oxides,
ozone and CFCs. These gases
are “greenhouse” gases, as they
absorb solar energy and reflect
it back to earth.
∙
Greenhouse gases help keep the earth retain heat, creating a
hospitable temperature range.
Earth’s Climate is Variable: There are 7-10 different biomes.
∙
Each biome has a
distinct climate
pattern (seasonal vs.
constant rainfall and
temperature pattern),
productivity,
population density
and contains similar
flora/fauna/food
webs.
$ What causes the pattern of biomes throughout the world?
Climate Basics:
Biome patterns are explained by geological factors: The earth’s tilt
and rotation about the sun, latitude, altitude, proximity to bodies of
water or mountain ranges.
∙
The earth is tilted on its axis.
Equatorial regions have
consistent sunlight and temp.
patterns.
∙
Northern and southern
hemispheres experience summer
(when tilted toward the sun) and winter (when tilted away from
the sun) with variable temperature patterns. They have cold
winters and warm summers.
Consistent heat in equatorial latitudes drive the earth’s air
circulation patterns.
∙ At the equator, most of the
earth’s surface is water.
∙ Temperatures are always
warm, and the warm air rises
consistently.
∙ Air cools as it rises,
condensing to produce heavy rain
that is typical of tropical
climates.
∙
This is known as the Hadley convection cell, and its consistent
pattern drives air circulation across our planet.
The mid-latitudes experience distinct winter and summer
weather patterns and have a highly variable rainfall pattern.
∙
Air from the Hadley cell descends at 30 oN
and 30 oS. This air warms as it nears earth,
and its saturation point increases. Thus,
little rainfall occurs and the world’s great
deserts are typically found at 30 oN and 30
o
S.
∙
Air rises again at 60 oN and 60 oS, so regions in between 30o and
60o experience moderate seasonal rainfall. This circulation
pattern is known as the Ferrel cell.
∙
In these latitudes, presence of mountain ranges and/or proximity
to water cause highly variable rainfall and temperature patterns.
Polar regions have short summers, long winters and the cold air
holds little moisture before reaching saturation.
∙ The most northern and southern
air cell is called the polar cell.
Polar regions have very little
precipitation, mostly in the form of
snow.
∙ Cold temperatures allow
permanent ice caps to persist.
∙ Polar ice is a critical component
of earth’s climate: it reflects
sunlight and helps to counter-balance the greenhouse effect. This
phenomenon is known as albedo.
Within each air cell,
mountain ranges,
altitude and large
bodies of water
influence the basic
temperature and
rainfall patterns.
∙
High altitude biomes
generally have
cooler temperatures
and may block wind
patterns, thus limiting rainfall.
∙
Coastal regions have moderation of winter and summer
temperatures as well as additional moisture.
∙
Here is an example of the orographic effect: the impact of
mountain range placement on precipitation. Note that Reno and
Sacramento have less rainfall than the Bay Area, because they are
on the leeward (sheltered) sid e of the mountains.