WHAT CAUSES CLIMATE CHAPTER 4 – SECTION 1 Weather is day-to-day events. The weather may be cloudy...
21
WHAT CAUSES CLIMATE CHAPTER 4 – SECTION 1
WHAT CAUSES CLIMATE CHAPTER 4 – SECTION 1 Weather is day-to-day events. The weather may be cloudy and rainy one day and clear and sunny the next. Weather
Weather is day-to-day events. The weather may be cloudy and
rainy one day and clear and sunny the next. Weather refers to the
condition of the atmosphere at a particular place and time.
Climate, on the other hand, refers to the average, year-after-year
conditions of temperature, precipitation, winds, and clouds in an
area. Two main factorstemperature and precipitation determine the
climate of a region. A climate region is a large area with similar
climate conditions throughout.
Slide 4
FACTORS AFFECTING TEMPERATURE The main factors that influence
temperature are latitude, altitude, distance from large bodies of
water, and ocean currents. In general, climates of locations
farther from the equator are cooler than climates of areas closer
to the equator. Why is this? The suns rays hit Earths surface most
directly at the equator. At the poles, the same amount of solar
radiation is spread out over a larger area, and therefore brings
less warmth.
Slide 5
Latitude is the distance from the equator, measured in degrees.
Based on latitude, Earths surface can be divided into the three
temperature zones. The tropical zone is the area near the equator,
between about 23.5 north latitude and 23.5 south latitude. The
tropical zone receives direct or nearly direct sunlight all year
round, making climates there warm.
Slide 6
In contrast, the suns rays always strike at a lower angle near
the North and South poles. As a result, the areas near both poles
have cold climates. These polar zones extend from about 66.5 to 90
north and 66.5 to 90 south latitudes.
Slide 7
The temperate zones are between the tropical and the polar
zones from about 23.5 to 66.5 north and 23.5 to 66.5 south
latitudes. In summer, the suns rays strike the temperate zones more
directly. In winter, the suns rays strike at a lower angle. As a
result, the weather in the temperate zones ranges from warm or hot
in summer to cool or cold in winter.
Slide 8
ALTITU DE Altitude is a more important climate factor than
latitude. The temperature of the troposphere decreases about 6.5
Celsius degrees for every 1-kilometer increase in altitude. As a
result, highland areas everywhere have cool climates, no matter
what their latitude. At nearly 6 kilometers, the air at the top of
Mount Kilimanjaro is about 39 Celsius degrees colder than the air
at sea level at the same latitude.
Slide 9
DISTANCE FROM LARGE BODIES OF WATER Oceans or large lakes can
also affect temperatures. Oceans greatly moderate, or make less
extreme, the temperatures of nearby land. Water heats up more
slowly than land; it also cools down more slowly. Therefore, winds
from the ocean keep coastal regions from reaching extremes of hot
and cold. Much of the west coasts of North America, South America,
and Europe have mild marine climates, with relatively warm winters
and cool summers.
Slide 10
The centers of North America and Asia are too far inland to be
warmed or cooled by the oceans. Most of Canada and Russia, as well
as the central United States, have continental climates.
Continental climates have more extreme temperatures than marine
climates. Winters are cold, while summers are warm or hot.
Slide 11
OCEAN CURRENTS Many marine climates are influenced by ocean
currents, streams of water within the oceans that move in regular
patterns. In general, warm ocean currents carry warm water from the
tropics toward the poles. Cold currents bring cold water from the
polar zones toward the equator. The surface of the water warms or
cools the air above it. The warmed or cooled air then moves over
the nearby land. So a warm current brings warm air to the land it
touches. A cold current brings cool air.
Slide 12
OCEAN CURRENTS
Slide 13
FACTORS AFFECTING PRECIPITATION The amount of rain and snow
that falls in an area each year determines how wet or dry its
climate is. But what determines how much precipitation an area
gets? The main factors that affect precipitation are prevailing
winds and the presence of mountains. Weather patterns depend on the
movement of huge air masses. Air masses are moved from place to
place by prevailing winds, the directional winds that usually blow
in a region. Air masses can be warm or cool, dry or humid. The
amount of water vapor in the air mass influences how much rain or
snow will fall.
Slide 14
FACTORS AFFECTING PRECIPITATION Warm air can carry more water
vapor than cold air can. When warm air rises and cools, water comes
out of the air as precipitation. For example, surface air near the
equator is generally hot and humid. As the air rises and cools,
heavy rains fall, nourishing thick tropical forests. In contrast,
sinking cold air is usually dry. Because the air becomes warmer as
it sinks, it can hold more water vapor. The water vapor stays in
the air and little or no rain falls -- The result may be a
desert.
Slide 15
FACTORS AFFECTING PRECIPITATION The amount of water vapor in
prevailing winds also depends on where the winds come from. Winds
that blow inland from oceans carry more water vapor than winds that
blow from over land. For example, the Sahara in Africa is near both
the Atlantic Ocean and the Mediterranean Sea. Yet the Sahara is
very dry. This is because few winds blow from the oceans toward
this area. Instead, the prevailing winds are the dry northeast
trade winds. The source of these winds is cool, sinking air from
southwest Asia.
Slide 16
MOUNTAIN RANGES A mountain range in the path of prevailing
winds can also influence where precipitation falls. When humid
winds blow from the ocean toward coastal mountains, they are forced
to rise up to pass over the mountains. The rising warm air cools
and its water vapor condenses, forming clouds. Rain or snow falls
on the windward side of the mountains, the side the oncoming wind
hits.
Slide 17
MOUNTAIN RANGES By the time the air reaches the other side of
the mountains, it has lost much of its water vapor, so it is cool
and dry. The land on the leeward side of the mountainsdownwindis in
a rain shadow.
Slide 18
MICROCLIMA TES Have you ever noticed that it is cooler and more
humid in a grove of trees than in an open field? The same factors
that affect large climate regions also affect smaller areas. A
small area with specific climate conditions may have its own
microclimate. Inland mountains, lakes, forests, and other natural
features can influence climate nearby, resulting in a
microclimate.
Slide 19
MICROCLIMA TES You might find a microclimate in a downtown area
with clusters of tall buildings, or on a windy peninsula jutting
out into the ocean. Even a small park, if it is usually sunnier or
windier than nearby areas, may have its own microclimate. The grass
on a lawn can be covered in dew and produce conditions like a rain
forest, while the pavement in the parking lot is dry, like a
desert.
Slide 20
THE SEASONS Although you can describe the average weather
conditions of a climate region, these conditions are not constant
all year long. Instead, most places on Earth outside the tropics
have four seasons: winter, spring, summer, and autumn. You might
think that Earth is closer to the sun during the summer and farther
away during winter. If this were true, every place on Earth would
have summer at the same time. Actually, when it is summer in the
Northern Hemisphere it is winter in the Southern Hemisphere. So the
seasons are not a result of changes in the distance between Earth
and the sun.
Slide 21
TILTED AXIS The seasons are caused by the tilt of Earths axis
as Earth travels around the sun. The axis is an imaginary line
through Earths center that passes through both poles. Earths axis
is not straight up and down, but is tilted at an angle of 23.5. The
axis always points in the same directiontoward the North Star. As
Earth travels around the sun, the north end of the axis is pointed
away from the sun for part of the year and toward the sun for part
of the year.