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.
Section 12.3
Gathering Weather Data
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
Section 12.3
Gathering Weather Data
New Vocabulary
thermometer
hygrometer
barometer
radiosonde
anemometer
Doppler effect
Section 12.3
Gathering Weather Data
Data from Earth’s Surface
Two important factors in weather forecasting
are the accuracy of the data and the
amount of available data.
Section 12.3
Gathering Weather Data
Data from Earth’s Surface
Temperature and air pressure
A thermometer measures temperature
using either the Fahrenheit or Celsius
scale.
A barometer measures air pressure.
Section 12.3
Gathering Weather Data
Data from Earth’s Surface
Wind speed and relative humidity
An anemometer measures wind speed.
A hygrometer measures relative humidity.
Section 12.3
Gathering Weather Data
Data from Earth’s Surface
Automated Surface Observing System
The Automated Surface Observing System
(ASOS) gathers data in a consistent manner,
24 hours a day, every day. It provides
essential weather data for aviation, weather
forecasting, and weather-related research.
Section 12.3
Gathering Weather Data
Data from the Upper Atmosphere
The instrument used for gathering upperatmosphere data is a radiosonde.
A radiosonde’s sensors measure the air’s
temperature, pressure, and humidity.
Also wind speed and direction( by its
movement)
Section 12.3
Gathering Weather Data
Weather Observation Systems
Weather radar
A weather radar system detects specific
locations of precipitation.
The Doppler effect is the change in pitch or
frequency 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.
Section 12.3
Gathering Weather Data
Weather Observation Systems
Doppler radar
Analysis of Doppler radar data can be
used to determine the speed at which
precipitation moves toward or away
from a radar station.
Difference between radar and Doppler
radar.
Radar
Doppler radar
detects specific locations speed at which
precipitation moves
of precipitation.
toward or away from a
radar station.
Section 12.3
Gathering Weather Data
Weather Observation Systems
Weather satellites -3 types of imaging
1. Infra red, 2. visible light, 3.water vapor
imagery.
Some satellites use cameras that require
visible light to photograph Earth.
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
clouds but not necessarily precipitation.
Section 12.3
Gathering Weather Data
Weather Observation Systems
Weather satellites track clouds and water vapor.
Some weather satellites use infrared imagery
to make observations at night.
Objects radiate thermal energy at slightly
different frequencies. Infrared imagery detects
these different frequencies, which enables
meteorologists to map either cloud cover or
surface temperatures.
Section 12.3
Gathering Weather Data
Weather Observation Systems
Weather satellites
Another type of satellite imagery that is
useful in weather analysis and forecasting is
called water-vapor imagery.
Water-vapor imagery is a valuable tool for
weather analysis and prediction because it
shows moisture in the atmosphere, not just
cloud patterns.
Difference between weather radar and
weather satellite
Radar
Satellite
Tracks precipitation
Tracks clouds and moisture.
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.
Review Vocabulary
model: an idea, system, or mathematical
expression that represents an idea
Section 12.4
Weather Analysis and Prediction
Several methods are used to develop shortterm and long-term weather forecasts.
New Vocabulary
station model
digital forecast
isobar
analog forecast
isotherm
Section 12.4
Weather Analysis and Prediction
Surface Weather Analysis
Station models
A station model is a record of weather
data for a particular site at a particular
time.
Section 12.4
Weather Analysis and Prediction
Surface Weather Analysis
Station models
Meteorological
symbols are used
to represent
weather data in a
station model.
Advantages:
universal
language, more
info in less space.
Section 12.4
Weather Analysis and Prediction
Surface Weather Analysis
Plotting station model data
To plot data nationwide and globally,
meteorologists use lines that connect
points of equal or constant values.
Section 12.4
Weather Analysis and Prediction
Surface Weather Analysis
Plotting station model data
Lines of equal pressure are called isobars.
Lines of equal temperature are called
isotherms.
Section 12.4
Weather Analysis and Prediction
Surface Weather Analysis
Interpreting station model data
The weather map shows
isobars and air pressure
data for the continental
United States.
Section 12.4
Weather Analysis and Prediction
Surface Weather Analysis
Interpreting station model data
Using isobars, isotherms, and station model
data, meteorologists can analyze current
weather conditions for a particular location.
Section 12.4
Weather Analysis and Prediction
Types of Forecasts
Digital forecasts
A digital forecast is created by applying
physical principles and mathematics to
atmospheric variables and then making a
prediction about how these variables will
change over time.
Section 12.4
Weather Analysis and Prediction
Types of Forecasts
Analog forecasts
An analog forecast is based on a
comparison of current weather patterns to
similar weather patterns from the past.
Differences between digital and analog
forecasts.
Digital
Analog
By analyzing current weather data
By comparing current weather
patterns with similar patterns from the
past.
Section 12.4
Weather Analysis and Prediction
Short-Term Forecasts
The most accurate and detailed forecasts are
short term because weather systems change
directions, speeds, and intensities over time.
Section 12.4
Weather Analysis and Prediction
Long-Term Forecasts
Because it is impossible for computers to
model every variable that affects the
weather at a given time and place, all
long-term forecasts are less reliable than
short-term forecasts.
Short term forecasts are more reliable.
CH
Study Guide
Key Concepts
Section 12.3 Gathering
Weather Data
Accurate measurements of
atmospheric properties are a critical part of
weather analysis and prediction.
 To make accurate weather forecasts,
meteorologists analyze and interpret
data gathered from Earth’s surface by
weather instruments.
CH
Study Guide
Key Concepts
Section 12.3 Gathering
Weather Data
 A radiosonde collects upper-atmospheric data.
 Doppler radar locates where precipitation
occurs.
 Weather satellites use infrared, visible-light, or
water-vapor imagery to observe and monitor
changing weather conditions on Earth.
CH
Study Guide
Key Concepts
Section 12.4 Weather
Analysis and Prediction
Several methods are used to develop
short-term and long-term weather forecasts.
 A station model is used to plot different
weather variables.
 Meteorologists plot lines on a map that
connect variables of equal value to
represent nationwide and global trends.
CH
Study Guide
Key Concepts
Section 12.4 Weather
Analysis and Prediction
 Two kinds of forecasts are digital and analog.
 The longer the prediction period, the less
reliable the weather forecast.
CH
Meteorology
12.3 Section Questions
Which weather instrument is used to
measure wind speed?
a. barometer
b. thermometer
c. anemometer
d. hygrometer
CH
Meteorology
12.3 Section Questions
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.
CH
Meteorology
12.3 Section Questions
Why are weather satellites important
to forecasters?
CH
Meteorology
12.3 Section Questions
Answer: Satellites can monitor weather
conditions over large regions of Earth using
a variety of wavelengths. The satellites
provide information about cloud cover,
moisture, atmospheric circulation, and more,
which can be used together to provide
current and rapid forecasts.
CH
Meteorology
12.4 Section Questions
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
CH
Meteorology
12.4 Section Questions
Which weather forecast is usually the
most accurate?
a. one-day forecast
b. three-day forecast
c. seven-day forecast
d. thirty-day forecast
CH
Meteorology
12.4 Section Questions
How are digital forecasts made?
Possible answer: Digital forecasts are
made by using computers to model future
weather conditions based on current
weather data.
CH
Meteorology
Chapter Assessment
Questions
What characteristics describe a continental
tropical air mass?
a. cool and dry
b. hot and dry
c. mild and humid
d. hot and humid
CH
Meteorology
Chapter Assessment
Questions
A high-pressure system has moved directly
over a region. What weather condition most
likely exists in this region?
a. fair weather
b. steady rain
c. high winds
d. thunderstorms
CH
Meteorology
Chapter Assessment
Questions
Which type of wave is transmitted by weather
radar units?
a. X rays
b. sound waves
c. radio waves
d. infrared waves
CH
Meteorology
Chapter Assessment
Questions
Examine the isobar map. From approximately
which direction is the wind blowing in
central Ohio?
a. southwest
b. southeast
c. northwest
d. northeast
CH
Meteorology
Chapter Assessment
Questions
A warm, moist air mass is currently over a
region. What changes will occur as a strong
cold front advances over this region?
CH
Meteorology
Chapter Assessment
Questions
Answer: The front has a high temperature
contrast across it and a supply of moisture
in front of it. As the cold front advances,
uplift of moisture-laden air will occur and
thunderstorms will probably develop. Some
of these storms could be severe.
CH
Meteorology
Standardized Test
Practice
Which type of air mass forms over the Gulf
of Mexico and Caribbean Sea?
a. continental polar
b. continental tropical
c. maritime polar
d. maritime tropical
CH
Meteorology
Standardized Test
Practice
A frigid, winter air mass is moving south across
the central United States. Which feature can
most modify the characteristics of this air mass?
a. a large lake
b. tree-covered hills
c. snow-covered plains
d. a lowland area
CH
Meteorology
Standardized Test
Practice
Which winds converge and rise at the
intertropical convergence zone?
a. polar easterlies
b. westerlies
c. trade winds
d. jet streams
CH
Meteorology
Standardized Test
Practice
How is the path of a moving current of air in the
southern hemisphere affected by Earth’s rotation?
a. It curves to the right.
b. It curves to the left.
c. It curves upward.
d. It curves downward.
CH
Meteorology
Standardized Test
Practice
How does the polar jet stream affect weather
in the midlatitudes?
CH
Meteorology
Standardized Test
Practice
Possible answer: The jet stream marks the
boundary between colder polar air and
warmer subtropical air. Undulations in the jet
stream move cold air to warmer latitudes and
warm air to colder latitudes. Surface high- and
low-pressure systems also form and move
along the jet stream, so the jet stream guides
weather across the midlatitudes.