There are three basic climate groups. Group one has low-latitude climates, these
climates are controlled by the equator. Group two has mid-latitude climates, the
climates in this zone are affected by air masses being in constant conflict. Group
three has high latitude climates polar and arctic air masses are the main ones in this
Rainforests are a good example of tropical moist climates. Annual rainfall is
usually more than 100 inches with heavy rainfall year round. The temperature is
around 80 F all year and humidity is between 77 and 88%. High surface heat and
humidity form cumulus clouds early in the day nearly everyday.
Seasonal changes occur between wet tropical air masses and dry tropical air
masses. Therefore there is a very wet season and a very dry season. Trade winds
dominate during dry seasons. It gets slightly cooler during this dry season but will
become extremely hot just before the wet season.
These desert climates are found in low-latitude deserts. These latitude belts are
centered on the Tropics of Cancer and Capricorn. They coincide with the edge of
the equatorial subtropical high pressure belt and trade winds. Winds are light,
which allows for the evaporation of moisture in the intense heat. They normally
flow down so the area is barely ever hit by air masses that make rain. This makes
for a very dry heat. The dry arid desert is a true desert climate. It covers 12% of
the Earth’s land surface.
It has grasslands and is a semiarid climate. If it received less rain, the steppe
would be classified as an arid desert. With more rain it would be a tall grass
prairie. It is located in N. America and Eurasian continents. Moist ocean air
masses are blocked by mountains to the west and south. There mountains also
trap polar air in winter, making winters very cold. Summers are warm to hot.
This is a wet-winter, dry-summer climate. Very dry summers are caused by the
sinking aid of the subtropical highs and may last for up to five months. Plants
have adapted to the extreme difference in rainfall and temperature between
winter and summer seasons. Plants range from forests, woodland and scrub.
Fires are very common in this type of climate.
These dry climates are limited to the interiors of N. America and Eurasia. Ocean
air masses are blocked from this type of climate by mountains in the west and
south. This allows polar air masses to dominate in winter months. In the summer,
a local continental air mass is dominant. A small amount of rain falls during this
season. Annual temperatures range widely. Summers are warm to hot, but
winters are cold.
This climate is in the polar front zone the battleground of polar and tropical air
masses. Seasonal changes between summer and winter are very large, along
with daily temperatures which change often. A lot of rain falls year round. It goes
up during the summer because it invades tropical air masses. Cold winters are
caused by polar and arctic masses moving south.
This is a continental climate with long, very cold winters, and short, cool
summers. This climate is found in the polar air mass region. Very cold air masses
from the arctic often move in. The temperature range is larger than any other
climate. Rain increases during summer months, but annual rain is still small.
Much of this climate is considered humid, but large areas in western Canada and
Siberia get very little rain and fall into the subhumid or semiarid climate type.
The tundra climate is found in arctic coastal areas. Polar and arctic air masses
dominate the tundra climate. The winter season is long and brutal. A short, mild
season exists, but not a true summer season. Moderating ocean winds keep the
temperatures from being as severe as interior regions.
Highland climates are cool to cold, found in mountains and high plateaus.
Climates change rapidly on mountains, becoming colder the higher the altitude
gets. The climate of a highland area is closely related to the climate of the
surrounding biome. The highlands have the same seasons and wet and dry
periods as the biome they are in. Mountains climates are very important to
midlatitude biomes. They work as water storage areas. Snow is kept back until
spring and summer when it is released slowly as water through melting.
The intensity of solar radiation decreases at altitude increases
The sun is directly pointed closer to the equator and therefore it receives more
radiation and is warmer
You can tell by when you look into the sky and at certain points the sun appears
in different places, in the arctic circle and Antarctic circle the sun either never
sets or rises
The higher the place, the colder it is
Air temperature drops 3.5 degrees(F) every 1,000 feet of altitude
The temperature determines how much precipitation, like snow, will fall
Even in the tropics, mountaintops can be snowcovered
Surface features influence the climate, they can influence the development of
clouds and precipitation amounts
Warm humid air sweeps up the windward side of a mountain and as the air cools
clouds form and creates precipitation
The leeward slopes tend to be dry and
Rain shadows may stretch for miles behind the mountain
Ocean and lake surfaces warm and cool more slowly than land surfaces
The temperature of the water influences the air above it, so the areas downwind
of the body of water tend to have a milder climate
San Francisco and St. Louis are about the same latitude, so they receive the
same amount of solar radiation, but since San Fransisco is down wind of the
Pacific Ocean it has milder winters and cooler summers
Atmospheric circulation produces winds that distribute heat and moisture
Due to the trade winds the climates are different in different areas because they
create wind going in a certain direction and bringing influence from its origin with
volcanic eruptions cause more of a short term climate change
Eruptions can cause there to be a short period of cooling in the air
When sulfur gases combine with moisture they absorb some of the radiation from
the sun and can also reflect the radiation, therefore less radiation reaches the
surface creating a short period of a cooler climate
This short period can be from a few days to even a few years
The 1991 eruption of Mount Pinatube in the Philipines created a drop of 1.1
degrees(fahrenheit) for the folllowing couple of years
Normally ocean circulation changes are short term- a few years
The changes during El Nino can alter the climate for a few years
El Nino is a change between the tropical atmosphere and oceans, changes in the
air pressure over the Pacific can weaken the trade winds, or even make them
change direction.
When El Nino occurs then it changes the air and can create weather changes as
These can cause short and long term changes in the atmosphere and climate
Atmospheric CO2 causes the greenhouse effect, where it will reflect and trap the
radiation from the sun into the atmosphere
Human activiy is increasing the CO2 levels in the atmosphere which causes
fluctuations in the climate
Also there is insight of volcanic activity on the ocean floor that released
tremendous amounts of CO2 that occurred about 100 million years ago, so the
earth also naturally goes through changes
Milutin Milankovitch proposed that there are three orbit variations that affect the
sunlight distribution
• Precession(wobbling) of the earth’s axis
• Tilt changes
• Path of the orbit, changing
Changes of these factors can influence the amount of solar radiation
reaching different spots on the earth which creates climate changes,
although these create short changes most of the time it is believed to be a
cycle so the earth has gone through these climate changes in the past
An extremely slow process that influences climate over millions of years
As the continents move due to plate tectonics their climate changes
This explains why there are tropical fossils found in Antarctica and ocean
sediment and shells on the tops of mountains
This is a very slow process in altering the climate
It alters an areas altitude and changes the temperature
The rise of the himalaya and colorado plateau may have happened within the
past 10 million years and some scientists think that the rise of these massive
landforms altered the wind belts, which made the earth’s climates more diverse
We alter the climate in more ways than one
When we build cities, clear forests, and burn oil and other natural gases it can
change the climate
Cities have a warmer and drier area than the surrounding countryside
Large urban areas affect the areas downwind of them because of the pollution
including smoke and fuel gases
Burning fossil fuels contributes to the rising CO 2 amounts in the atmosphere
Clearing forests reduces the rate at which CO 2 is removed from the air because
trees and other plants remove it during photosynthesis and emit oxygen
Some climatologists say that there is a natural fluctuation of the temperature and
that human activity isn’t contributing to global warming
World book encyclopedia 2007 edition volume 9: H pages 676-679

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