Download Pearson Prentice Hall Physical Science: Concepts in Action

Pearson Prentice Hall
Physical Science: Concepts in Action
Chapter 24
Weather and
Climate
24.1 The Atmosphere
• Objectives:
• 1. Describe Earth’s atmosphere
and explain how it is essential to
life
• 2. Describe the layers of the
atmosphere and their properties
Atmosphere is Essential to Life
• Earth’s atmosphere forms a protective
boundary between Earth and space and
provides conditions that are suitable for life
• Earth’s atmosphere is a mixture of nitrogen,
oxygen, water vapor and many other gases
in which tiny solid and liquid particles are
suspended
• Earth’s atmosphere is composed of about
78% nitrogen and 21% oxygen
• All other elements are called trace gases
• Definition: air pressure is the force exerted
by the weight of a column of air on a surface
• At sea level air pressure = 101.3 kPa =
760mm Hg = 1 atm
• As altitude increases, air pressure and
density decrease
• Definition: a barometer is an instrument
used to measure air pressure
Layers of Atmosphere
• There are 4 layers of atmosphere:
• 1. troposphere is the atmospheric layer
closest to Earth’s surface where nearly all
weather occurs (it’s where we live)
• Definition: weather is the condition of the
atmosphere in a particular place at a
particular time
• The troposphere gets cooler with increasing
altitude, but temperature inversions can occur
• Temperature inversion is the atmospheric
condition in which warm air traps cooler air
near Earth’s surface
• 2. Stratosphere is the layer that contains the
ozone layer and extends upward from the
troposphere to an altitude of 50 km
• Ozone is the form of atmospheric highly
reactive oxygen gas that has three atoms per
molecule – O3
• The ozone layer is a protective layer when it is
located in the stratosphere
• Ozone absorbs harmful ultraviolet (UV)
radiation from the sun when located in the
stratosphere
• Ozone is harmful to life when it is located in
the troposphere
• Today, we know that man made
chemicals can deplete the ozone layer
• The ozone layer is located in the
upper stratosphere and they absorb
ultraviolet radiation from the sun
preventing DNA damage to living
organisms’ cells’
• Chlorofluorocarbons, CFCs, are
believed to be the main culprit and
they have been banned in the United
States
• 3. mesosphere is the coldest layer located
above the stratosphere
• 4. thermosphere is the atmospheric layer above
the mesosphere and starts at an altitude of about
80 km
• The air is very thin in the thermosphere
• The outmost portion at about 80 km (298 mi) is
the exosphere (not a distinct layer) where some
gases escape Earth’s gravitational pull and exit into
space
• Ionosphere (not a distinct layer) is when solar
energy absorbed in lower thermosphere & upper
mesosphere forms electrically charged ions
• The ionosphere reflects radio waves, keeping
them form escaping into space
• Ionosphere is where the aurora can be seen
around Earth’s poles
• Auroras are light displays caused by the sun
hitting atoms
• Earth began to solidify 4.4 billion years ago,
and later bacteria came
• Then, 2.5 billion years ago, the first
photosynthetic plants appeared and began to
contribute oxygen to Earth’s atmosphere
• The atmosphere gradually
accumulated oxygen until about 350
million years ago when the oxygen
reached “modern” levels
• Aerobic, oxygen breathing organisms
evolved leading to a balance
• Animals breathe oxygen by respiration
and exhale carbon dioxide as waste
• Plants use the carbon dioxide and
oxygen is their waste product
24.2 The Sun and the Seasons
• Objectives:
• 1. Describe how Earth moves
through space and explain how
seasons are caused by the tilt of
Earth’s axis
• 2. Explain why different latitude
zones have different average
temperatures
Seasons
• Earth moves in 2 ways: rotation and revolution
• Definition: rotation is the spinning of Earth on its
axis
• Definition: revolution is the movement of one
body in space around another
• Earth’s rotation causes day and night
• Earth revolves around the sun
• Scientists use line of latitude to mark out three
different types of regions within which
temperatures are generally similar: the tropic,
temperate and polar zones
• The tropic zone is generally warm
• The temperate zones are generally cooler
than the tropics
• The polar zones are at the north and south
poles and are cold
• The seasons are caused by the tilt of Earth’s
axis as it moves around the sun
• Earth’s tilt and rotation account for seasons
• Earth is tilted 23.5° from its perpendicular
on its axis
• Definition: a solstice are the two days each year when
the sun is directly overhead at 23.5°N or 23.5°S
• The longest day of the year is the summer solstice, June
21 (the first day of summer) in the northern
hemisphere
• The shortest day is the winter solstice in the northern
hemisphere, December 21(the first day of winter)
• Definition: an equinox occurs when hours of daylight
and nighttime are nearly equal
• Twice per year the days have equal hours of daylight
and night- the vernal equinox (first day of spring around
March 21), and the autumnal equinox (first day of fall)
occurring around September 22
24.3 Solar Energy and Winds
• Objectives:
• 1. Describe the processes by
which solar energy heats up the
troposphere
• 2. Identify local and global winds
and explain how they are
produced
Energy and the Troposphere
• Some solar energy that reaches Earth’s
atmosphere is reflected back, some is absorbed
by the atmosphere and some is absorbed by
Earth’s surface
• Definition: The greenhouse effect is the process
in which atmospheric gases trap some of the
energy from the sun in the troposphere and keep
Earth warm
• Without the greenhouse effect Earth would have
colder average temperatures
• With too much of the effect Earth’s temperatures
will rise
Local and Global Wind
• Energy is transferred within the
troposphere in 3 ways: radiation,
convection and conduction
• Winds are caused by differences in air
pressure
• Larger pressure differences produces
stronger winds
• Definition: a local wind is a wind that
blows over a short distance
• The breezes that occur where land meets a large
body of water are local winds
• Definition: a sea breeze is the cooler air over the
water that flows toward the land
• Definition: a land breeze is the higher density
cool air over land that moves toward water
• Winds are named for the direction from which
they originate (sea breezes start at the ocean
and land breezes begin over land)
• Definition: global winds are winds that blow
over long distances from a specific direction
• Global winds move in a circular band motion
called convection cells
• Global winds
are caused by
unequal
heating of
Earth’s
surface
across a large
region
• Trade winds,
westerlies
and polar
easterlies are
global winds
• The direction of wind movement is
influenced by Earth’s rotation in a
phenomenon called the Coriolis effect
• Definition: Coriolis effect is the change in
the direction of an object’s path due to
Earth’s rotation
• Winds moving south from the equator
move to the left (counter clockwise)
while moving north in the northern
hemisphere, winds curve to the right
(clockwise)
• There is a global pattern to the wind
• Temps at the equator tend to be warmer, so
air there rises causing a low pressure belt
• In the northern hemisphere, the air sinks
creating a high pressure belt
• Air flows from north to south, from high to
low pressure converging at the poles in a low
pressure belt
• Each hemisphere completes 3 of these
circulation pattern loops called convection
cells
• Definition: a monsoon is a wind system that
is characterized by seasonal reversal of
direction
• Monsoons are similar to sea and land
breezes except they occur on a much larger
scale and over a greater period of time
• Definition: a jet stream is a belt of highspeed wind in the upper troposphere
• Jet streams are caused by great differences
in air pressure that develops over high
altitudes
24.4 Water in the Atmosphere
• Objectives:
• 1. Explain condensation in the
atmosphere and describe the
formation and characteristics of
basic cloud forms
• 2. Identify the common types of
precipitation and explain how
they form
Condensation and Basic Clouds
• Definition: humidity is the amount of water
vapor in the air
• Definition: relative humidity is the ratio of the
amount of water vapor in the air to the
maximum amount of water vapor that could
exist at that temperature
• Relative humidity is always a percentage
• Definition: dew point is the temperature at
which the air becomes saturated with water
vapor
• Water vapor typically condenses as dew, frost,
clouds or fog
• Definition: a cloud is a dense, visible mass of
tiny water droplets or ice crystals that are
suspended in the atmosphere
• Definition: fog is a cloud that is near or
touching the ground
• Clouds form as warm, moist air rises and
water vapor condenses in the atmosphere
• There are three basic cloud types: stratus,
cumulus and cirrus
• Cirrus are the highest (6000 – 11,000 km above
Earth) & are thin & wispy
• Status are sheetlike & layered occurring between
the surface to 6 km up
• Cumulus clouds are white and fluffy with flat
bottoms (the point where rising air begins to
condense) forming from 500 m – 12 km above
Earth
• -nimbo or –nimbus added to a cloud’s name means
that the cloud produces precipitation
• Middle level clouds that occur at altitudes between
2000 – 6000 meters are given the prefix alto• Cirro- is used to describe high altitude clouds
Precipitation
• The most common types of precipitation are rain,
snow, hail, sleet and freezing rain
• Rain usually forms in nimbostratus or
cumulonimbus clouds
• Def: Snow is actually ice crystals called snowflakes
• Def: Hail is solid pieces of ice more than 5 mm in
diameter
• It comes from cumulonimbus clouds
• Def: Sleet is ice particles less than 5 mm in
diameter
• Def: Freezing rain is rain that freezes after hitting
the surface
24.5
Weather Patterns
• Objectives:
• 1. Explain how air masses form and
how they are classified
• 2. Describe the four types of fronts,
and the weather associated with each
• 3. Describe cyclones and anticyclones
• 4. Describe the major types of storms
and how they are formed
Air Masses
• An air mass forms when a large body of air becomes
fairly stationary over a region of Earth’s surface or
as air moves over a large, uniform region like an
ocean
• Meteorologists track weather by studying the
movement of air masses
• Air masses are large bodies of air with uniform
temperature and moisture content
• Air mass interactions have predictable effects on
weather
• Def: A front is the boundary between air masses of
different densities
Four Types of Fronts
• The four types of fronts are warm,
cold, stationary and occluded
• In a warm front a mass of warm air
moves over a slower mass of cool air
causing clouds to form as the warm
front cools
• As time passes, nimbostratus clouds
may release snow or rain for one to
two days
• In a cold front, the forward edge of the front
moves under a slower moving mass of warm
air which pushes the cold front up forming
clouds sometimes producing high winds,
thunderstorms and tornadoes
• A stationary front occurs when two air masses
meet & move side by side along the front
producing conditions similar to a warm front
• An occluded front forms when a warm air
mass is caught between two cooler air masses
• The colder air masses force the warm air mass
to rise, trapping it between the two cold air
masses
Cyclones and Anticyclones
• Definition: a cyclone is a weather system
with a center of low pressure
• Cyclones are associated with clouds,
precipitation, and stormy weather
• Definition: a weather system with a swirling
center of high air pressure is called an
anticyclone
• The weather associated with an anticyclone
includes clear skies, very little precipitation
and generally calm conditions
Storms
• Definition: a thunderstorm is a small weather
system that includes thunder and lightning
• Lightning is a discharge of electrical energy
• Thunder is the noise made when electrical
charges move through the air along the path
of the lightning
• Thunderstorms form when columns of air rise
within a cumulonimbus cloud
• Twister is a common name for a tornado
• Definition: a tornado is small but intense
windstorm that takes the form of a rotating
column of air that touches the ground
• Tornadoes are funnels of high-speed rotating
wind that extend down from thunderclouds
• On Earth they are most common in the United
States in early spring and summer
• They usually form along a front between cool,
dry northern air and warm, moist southern air
creating the rotation
• A funnel cloud is a tapered column of water that
is the beginning of a tornado
• Thunderstorms and tornadoes are associated
with cyclone of the middle latitudes
• Tornadoes are dangerous and you should seek
shelter or lie in a ditch if you are outside when
one strikes
• Definition: a hurricane is a large tropical
cyclone with winds of at least 74 mph
• In the Caribbean they are called cyclones
(Atlantic) & in the Indian Ocean they are
called typhoons
• In the northern hemisphere they typically
occur during late summer and early fall
• Hurricanes begin as tropical depressions from
warm ocean water evaporating, vapor rising
creating intense low pressure areas
• Hurricanes are powered by energy released as
water vapor condenses to form clouds
• Its eye is calm and cloud-free
24.6 Predicting the Weather
• Objectives
• 1. Interpret weather map
features and describe the
technology used to forecast
weather
Forecasting
• Definition: meteorology is the study of Earth’s
atmosphere
• Meteorologists use many technologies to help
predict the weather, including Doppler radar,
automated weather stations and high-speed
computers
• Doppler radar uses the Doppler effect
• It bounces radio waves off particles of
precipitation in moving storms and measures
the frequency of the waves that return
• Weather satellites have been placed in
Earth’s orbit since the 1960s
• The satellites can “see” storm formation
including hurricanes and measure cloud
cover, humidity, temperature and wind speed
• Weather stations have sensors that measure
temperature, precipitation, wind speed and
wind direction
• High-speed computers analyze weather
information and scientists make predictions
about the forecast
Weather Maps
• Weather maps are used by meteorologists to
prepare forecasts
• The maps have symbols for precipitation, wind
speed, cloud coverage, fronts & so on
• Def: Isobars are lines drawn on a weather map
connecting points of equal barometric or
atmospheric pressure
• The wind directions are slightly across the
isobars due to the Coriolis effect
• Def: isotherms are lines on a map that
connect points of equal air pressure
24.7 Climate
• Objectives:
• 1. Distinguish between weather
and climate and describe the
main factors that affect a region’s
climate
• 2. Compare climate variations
due to natural and human causes
Weather versus Climate
• Definition: Climate is the general weather
conditions over many years
• It is the average weather of a region
• Temperatures tend to be higher around the
equator producing a warm climate
• The two main factors that determine a
region’s climate are temperature and
precipitation
• Factors that affect a region’s temperature
include its latitude, distance from large bodies
of water, ocean currents and altitude
• Factors that affect a region’s precipitation
include its latitude, the distribution of air
pressure systems and global winds, and the
existence of a mountain barrier
• Definition: a desert is a dry region with less
than 25 cm of rain per year
• Def: Topography is the surface features of the
Earth
• It is hills, mountains, valleys, and flat surface
• Mountains an have a profound effect on
climate
• Tall mountains force air over them while
rising air forms clouds causing precipitation
on the side where the air was rising and
cool, dry air on the other side of the
mountain where the air descends
• Climates change over the long term, and
they vary somewhat over the short term
• Def: ice ages are periods when climates
were colder than usual and glaciers covered
a large portion of Earth’s surface
• There have been many ice ages on Earth
• Def: El Niňo is a short-term natural climate
variation that occurs every 8 years off the
coast of South America
• El Niňo causes a periodic warming of the
central and eastern Pacific Ocean
disrupting the fishing industries for the
countries off the western coast of South
America
• The mechanism is not well understood but
ocean currents and wind patterns change
at that time
• Recall that greenhouse gases include water
vapor and CO2 among others
• The greenhouse effect is the process in which
atmospheric gases trap some of the energy from
the sun in the troposphere and keep Earth
warm
• Without the greenhouse effect Earth would
have colder average temperatures
• With too much of the effect Earth’s
temperatures will rise
• Def: global warming is a process in which CO2
levels increase enough that the temperature of
the atmosphere rises
• There has been a well- documented rise
in the level of CO2 in the last 100 years
believed to have come from the burning
of coal, oil and natural gas (hydrocarbon
fossil fuels)
• Some scientists think this rise in CO2
levels is contributing to the greenhouse
effect and might give rise to the
phenomenon called global warming
• Global warming might cause ice caps to
melt, oceans to rise droughts in some
places
• Global climate changes over time
• There have been many ice ages on Earth
which coincide with the sunspot cycle
(as do warming cycles)
• Increased carbon dioxide may
eventually lead to a warming effect
caused by the greenhouse effect
• Earth’s climate will continue to change