Ch. 12 Meteorology
Section 12.1: The Causes of Weather
Objectives
• Compare and contrast weather and climate.
• Analyze how imbalances in the heating of Earth’s surface create weather.
• Describe how air masses form.
• Identify five types of air masses.
Main Idea
• Air masses have different temperatures and amounts of moisture because of the uneven
heating of Earth’s surface.
Review Vocabulary
• heat: transfer of thermal energy from a warmer material to a cooler material
What is meteorology?
• _______________ is the study of ______________ phenomena.
• The root word of _____________ is the Greek word meteoros, which means
_________ ___________________________.
• Weather versus climate
o ________ - _______ variations in atmospheric phenomena that ____________
and affect the _____________ and ______ on Earth are called __________.
o ___________ is the ________ - ________ average of variations in weather
for a particular area.
Heating Earth’s Surface
• Imbalanced heating
o One reason that temperatures may _______ from location to location at a certain
time of year is that Earth’s _______ of ___________ is tilted relative to the
plane of Earth’s _________.
o ________ radiation is unequal partly due to the changing _________ of
incidence of the ___________. The ___________ the area covered by solar
radiation, the ___________ the amount of heat per unit of area.
• Thermal energy redistribution
o The constant movement of ______ redistributes thermal _________ around the
world.
o Weather—from thunderstorms to large-scale weather systems—is part of the
constant redistribution of Earth’s __________ _________.
Air Masses
• An air mass is a large __________ of air that has the same characteristics, such as
___________ and ______________, as its source region.
• A __________ region is the area over which an air mass forms.
• Types of air masses
o The origins of ___________ ___________ air are tropical bodies of water.
•
o The southwestern United States and Mexico are the source regions of continental
___________ air, which is ______ and ______, especially in summer.
o Maritime polar air masses form over the _______ waters of the North
___________ and North ___________.
o Continental polar air masses form over the interior of ___________ and
___________, and carry ___________ air southward in the winter.
o Earth’s ice- and snow-covered surfaces above 60 N latitude in Siberia and the
Arctic Basin are the source regions of ___________ air masses.
Air mass modification
o When an air mass travels over ___________ or ___________ that has
characteristics different from those of its source ___________, the air mass can
___________ some of the characteristics of that land or water and undergo
modification.
o As the cold, continental ___________ air moves over the ___________ Great
Lakes, the air gains ___________ ___________ and ___________. This
modified air cools as it is ___________ and produces lake-effect snows.
12.1 Section Questions
1. Climate is the long-term average of weather.
a.
true
b.
false
2. Which type of air mass forms over the North Pacific Ocean?
a.
arctic
b.
continental polar
c.
maritime polar
d.
maritime tropical
3. Why does Earth’s equator receive more solar energy than Earth’s poles?
Ch. 12 Meteorology
Section 12.2: Weather Systems
Objectives
• Compare and contrast the three major wind systems.
• Identify four types of fronts.
• Distinguish between high- and low-pressure systems.
Main Idea
• Weather results when air masses with different pressures and temperatures move, change,
and collide.
Review Vocabulary
• convection: the transfer of thermal energy by the flow of a heated substance
Global Wind Systems
• The directions of Earth’s ___________ are influenced by Earth’s ___________.
• This Coriolis effect results in ___________ and ___________ moving in an apparent
___________ path rather than a ___________ line.
Global Wind Systems
• The ___________ of Earth’s wind systems, such as the polar easterlies and the trade
winds, vary with the ___________ in which they occur.
• Polar easterlies
o The polar easterlies are the wind zones between _____ N latitude and the North
Pole, and _____ S latitude and the South Pole.
• Prevailing westerlies
o The prevailing westerlies are the wind systems on Earth located between latitudes
_____ N and _____ N, and _____ S and _____ S.
• Trade winds
o Between latitudes _____ N and _____ S are two circulation belts of wind
known as the ___________ winds.
o Near latitudes 30 N and 30 S, the sinking air associated with the trade winds
creates an area of high ___________. This results in a belt of weak surface
winds called the ___________ latitudes.
o Trade winds from the __________ and the ___________ meet and join near the
___________. The air is forced upward, which creates an area of low pressure.
o This process, called ______________, can occur on a small or large scale.
Near the equator, it occurs over a large area called the _________________
convergence zone (ITCZ).
Jet Streams
• A large temperature gradient in _________-level air combined with the Coriolis effect
results in strong westerly winds called ______ ___________.
• A jet stream is a narrow band of ___________, ___________ -altitude, westerly
___________.
•
•
•
Weather in the ___________ latitudes is strongly influenced by ___________ moving, ___________ -altitude jet streams.
Types of jet streams
o The major jet streams, called the ___________ jet streams, ___________ the
polar easterlies from the prevailing westerlies.
o The minor jet streams are the _____________ jet streams. They occur where
the trade winds ___________ the prevailing westerlies.
Jet streams and weather systems
o ___________ form along jet streams and can generate ___________ -scale
weather systems.
o Jet streams affect the ___________ of weather systems by ___________ air
of different temperatures from one region of Earth to another.
Fronts
• A collision of two air masses forms a ___________—a narrow region between two air
masses of different ___________.
• Cold front
o When ___________, dense air displaces ___________ air, it forces the warm
air, which is less dense, up along a steep slope. This type of collision is called a
_________ front.
• Warm front
o Advancing ___________ air displaces ___________ air along a warm front.
A ___________ front develops a gradual boundary slope.
• Stationary front
o When two air masses ___________ but neither ___________, the boundary
between them ___________. This stationary front frequently occurs between
two modified air masses that have small ______________ and ___________
gradients between them.
• Occluded front
o Sometimes, a cold air mass moves so ___________ that it overtakes a warm
front and forces the warm air upward. As the warm air is lifted, the advancing
cold air mass collides with the cold air mass in front of the warm front. This is
called an ___________ front.
Pressure Systems
• Sinking or rising air, combined with the Coriolis effect, results in the formation of
rotating _______- and ______-pressure systems in the atmosphere.
• Low-pressure systems
o In surface low-pressure systems, air _________. When air from outside the
system replaces the rising air, this air spirals inward toward the center and then
upward.
• High-pressure systems
o In a surface high-pressure system, ___________ air moves away from the
system’s center when it reaches Earth’s surface.
•
In the ___________ hemisphere, winds move counterclockwise around a ______pressure center, and clockwise around a _______-pressure center.
12.2 Section Questions
1. Along which type of weather front does one cold front overtake another cold front?
a.
cold front
b.
warm front
c.
stationary front
d.
occluded front
2. Which description characterizes a low-pressure center in the northern hemisphere?
a.
Air spirals out and rises.
b.
Air spirals in and rises.
c.
Air spirals out and sinks.
d.
Air spirals in and sinks.
3. At which latitudes are the horse latitudes?
a.
at about 10 N and 10 S
b.
at about 30 N and 30 S
c.
at about 60 N and 60 S
d.
at about 80 N and 80 S
Ch. 12 Meteorology
Section 12.3: Gathering Weather Data
Objectives
• State the importance of accurate weather data.
• Summarize the instruments used to collect weather data from Earth’s surface.
• Analyze the strengths and weaknesses of weather radar and weather satellites.
Main Idea
• Accurate measurements of atmospheric properties are a critical part of weather analysis
and prediction.
Review Vocabulary
• temperature: the average thermal energy of the particles that make up a substance
Data from Earth’s Surface
• Two important factors in weather forecasting are the ___________ of the data and the
___________ of available data.
• Temperature and air pressure
o A ______________ measures temperature using either the Fahrenheit or
Celsius scale.
o A ______________ measures air pressure.
• Wind speed and relative humidity
o An ______________ measures wind speed.
o A ______________ measures relative humidity.
• Automated Surface Observing System
o The Automated Surface Observing System (ASOS) gathers data in a consistent
manner, 24 hours a day, every day. It provides essential weather data for
____________, weather ______________, and weather-related research.
Data from the Upper Atmosphere
• The instrument used for gathering upper-atmosphere data is a ______________.
• A radiosonde’s sensors measure the air’s ______________, ______________, and
______________.
Weather Observation Systems
• Weather radar
o A weather radar system detects specific locations of ______________.
o The Doppler effect is the change in ________ or ____________ that occurs
due to the relative motion of a wave, such as sound or light, as it comes toward or
goes away from an observer.
o Analysis of Doppler radar data can be used to determine the ________ at which
precipitation moves toward or away from a radar station.
• Weather satellites
o Some weather satellites use __________ imagery to make observations at night.
o Objects radiate thermal _________ at slightly different frequencies. Infrared
imagery detects these different ______________, which enables
meteorologists to map either cloud cover or surface temperatures.
o Some satellites use __________ that require visible light to photograph Earth.
o These digital photos are sent back to ground stations, and their data are plotted on
maps. Unlike weather radar, which tracks precipitation but not clouds, satellites
track __________ but not necessarily ______________.
o Another type of satellite imagery that is useful in weather analysis and forecasting
is called ________-________ imagery.
o Water-vapor imagery is a valuable tool for weather ______________ and
______________ because it shows ___________ in the atmosphere, not just
cloud patterns.
12.3 Section Questions
1. Which weather instrument is used to measure wind speed?
a.
barometer
b.
thermometer
c.
anemometer
d.
hygrometer
2. Doppler radar data show that the return echo from one side of a storm has a shorter
wavelength than the emitted wave. What can be concluded about the reflecting particles?
a.
They are very small.
b.
They are very large.
c.
They are moving toward the station.
d.
They are moving away from the station.
3. Why are weather satellites important to forecasters?
Ch. 12 Meteorology
Section 12.4: Weather Analysis and Prediction
Objectives
• Analyze a basic surface weather chart.
• Distinguish between digital and analog forecasting.
• Describe problems with long-term forecasts.
Main Idea
• Several methods are used to develop short-term and long-term weather forecasts.
Review Vocabulary
• model: an idea, system, or mathematical expression that represents an idea
Surface Weather Analysis
• Station models
o A __________ ________ is a record of weather data for a particular site at a
particular time.
o Meteorological __________ are used to represent __________ data in a
station model.
• Plotting station model data
o To plot data _____________ and ____________, meteorologists use lines
that connect points of ________ or constant values.
o Lines of ________ pressure are called __________.
o Lines of ________ temperature are called ______________.
• Interpreting station model data
o The weather map shows ____________
and _______ _____________ data for
the continental United States.
o Using ____________, _____________,
and station model data, meteorologists can
analyze ______________ weather
conditions for a particular location.
Types of Forecasts
• Digital forecasts
o A ______________ forecast is created by applying ______________
principles and mathematics to ______________ variables and then making a
______________ about how these variables will ____________ over time.
• Analog forecasts
o An ______________ forecast is based on a comparison of ______________
weather patterns to ______________ weather patterns from the __________.
Short-Term Forecasts
• The most ______________ and ______________ forecasts are ______________
term because weather systems change ______________, ______________, and
______________ over time.
Long-Term Forecasts
• Because it is ______________ for computers to model every ______________ that
affects the weather at a given time and place, all long-term forecasts are ________
reliable than short-term forecasts.
12.4 Section Questions
1. What is an isobar?
a.
a line of constant altitude
b.
a line of constant temperature
c.
a line of constant pressure
d.
a line of constant moisture
2. Which weather forecast is usually the most accurate?
a.
one-day forecast
b.
three-day forecast
c.
seven-day forecast
d.
thirty-day forecast
3. How are digital forecasts made?