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Question: What can be learned from the information on a weather map?
WEATHER FORECASTS
meteorologist – scientist who study the causes of weather and try to predict it; use
maps, charts and computers to analyze data to prepare weather forecasts
surface report – description of a set of weather measurements made on Earth’s surface
upper-air report – describes wind, temperatures, and humidity conditions above Earth’s
surface
Doppler radar – specialized type of radar that can detect precipitation as well as the
movement of small particles, which can be used to approximate wind speed
station models – diagram that displays data from many different weather measurements
for a particular location:
isobars – lines joining places on a map that have the same air pressure
isotherms – lines joining places that have the same temperature
Question: What are the major types of air masses in North America and how do they
move?
WEATHER PATTERNS
high-pressure system – large body of circulating air with high pressure at its center and
lower pressure outside the system; brings sunshine and good weather
low-pressure system – large body of circulating air with low pressure at its center and
higher pressure outside the system; brings clouds and precipitation
air mass – large bodies of air that have uniform temperature, humidity and pressure
Air masses are classified by temperature and moisture – those formed over water are
called maritime, those formed over land are called continental; warm masses are
tropical and cold are polar
In the continental United States, air masses are commonly moved by prevailing
westerlies and jet streams. Colliding air masses can form four types of fronts:
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cold fronts – cold air moves under warm air forcing warm air up
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warm front – move slowly and bring warm, humid air
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stationary front – forms when a cold mass meets a warm mass but neither have
enough force to move the other
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occluded front – warm air mass is caught between two cold air masses
storm – violent disturbance in the atmosphere called severe weather
•
thunderstorms – small storm accompanied by thunder and lightning formed from
large cumulonimbus clouds
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tornado – rapidly, whirling, funnel-shaped cloud that reaches down from a storm
cloud and touches the Earth’s surface formed when thunderstorm updrafts begin
to rotate
•
hurricane – intense tropical storm with winds exceeding 119 km/hr formed over
warm ocean water as a low-pressure area
•
blizzard – violent winter storm characterized by freezing temperatures, strong
winds and blowing snow
Question: How many climate regions are there?
CLIMATES OF EARTH
Scientists classify climates using a system developed by Wladimir Köppen around 1900
that uses two major factors: temperature and precipitation. The system identifies six
broad climate regions:
1. Tropical Climate
tropical wet – year-round heat and heavy rainfall; dense forests called rainforests
tropical wet-and-dry – have less rainfall and distinct dry and rainy seasons; savannas or
tropical grasslands found here
2. Dry Climate
arid regions – also called deserts get less than 25 cm of rain every year
semiarid regions – also called steppes, are usually located on the edges of deserts, enough
rainfall for short grasses to grow
3. Temperate Marine Climate – humid with mild winters
marine west coast – humid air brings cool, rainy summers and mild, rainy winters
humid subtropical – climates are wet and warm, but not as hot as tropics
Mediterranean – summers are drier and warmer, winters are cool and rainy
4. Temperate Continental Climate – only in Northern Hemisphere
humid continental – constantly changing weather
subarctic – line north of humid continental; summers are short winters are long and
bitterly cold
5. Polar Climate
ice caps – covered with ice and snow and always at or below freezing
tundra – short, cool summers followed by bitterly cold winters
6. Highlands – temperature falls as altitude increases, so highland regions are colder
than regions that surround them
Question: What affects climate?
FACTORS THAT INFLUENCE CLIMATE
climate – the long-term average weather conditions that occur in a particular region;
determined by two main factors: temperature and precipitation
microclimate – small areas with climate conditions that differ from those around them
Main factors that influence temperature:
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latitude – Earth’s surface is divided into three temperature zones based on
latitude
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tropical zone (23.5ᵒN – 23.5ᵒS latitude) – area near the equator that has warm
climate since it receives direct sunlight all year
•
polar zone (66.5ᵒ-90ᵒN lat to 66.5ᵒ-90ᵒS lat) – cold climates because sun strikes
ground at lower angle
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temperate zones (23.5ᵒ-66.5ᵒN to 23.5ᵒ-66.5ᵒS lat) – between the polar and tropical
zones with weather that ranges from warm in summer to cold in winter.
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altitude – climate factor because air temperature decreases as altitude increases
•
distance from oceans and lakes – large bodies of water influence temperatures
because water heats up and cools down more slowly than land
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marine climates – relatively warm winters and cool summers
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continental climates – occur in inland areas and are often characterized by cold
winters and warm or hot summers.
•
ocean currents – currents cool or warm air above them, bringing warm or cooled
air to the land it touches.
Main factors that affect precipitation:
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prevailing winds – winds carry warm, moist air or cool air over land
•
presence of mountains – a mountain range in the path of prevailing winds
influences where precipitation falls
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rain shadows – areas of low rainfall on a downward, or leeward side of the
mountain
•
seasons – sea and land breezes over a large region that change direction with the
seasons are called monsoons
Question: How have humans impacted climate change?
CLIMATE CYCLES & RECENT CLIMATE CHANGE
Earth experiences many climate changes in its history. Scientists use evidence from ice
cores, or ice drilled from layers in glaciers, fossilized pollen, ocean sediments and
growth rings of trees to gain information on past climates.
Long-Term Cycles
Ice ages – long cold periods lasting from hundreds to millions of years when glaciers
cover much of Earth
interglacials – long warm periods that occur between ice ages
Short Term Cycles
seasons – short periods of climate change due to amount of solar energy an area receives
during different times of the year
El Niño – an occasional climatic event (occurs every 3-8 years) in which the trade winds
weaken, reversing the normal pattern of high and low pressures across the Pacific
Ocean
monsoon – a wind circulation pattern that changes directions with the seasons
Recent Climate Change
Average temperature on Earth has been increasing for the past 100 years, which is often
referred to as global warming
greenhouse gases – gases in the atmosphere that absorb Earth’s outgoing infrared
radiation; higher levels of greenhouse gases which include carbon dioxide (CO2) create
greater greenhouse effect
Humans have impacted climate change:
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burning of fossil fuels increases amount of carbon dioxide
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deforestation – the large-scale cutting and/or burning of forests which also
increases carbon dioxide
•
aerosols – tiny liquid or solid particles released from burning of fossil fuels which
prevent Sun’s energy from reaching Earth