CHAPTER 13 LESSON 3 Weather Weather Forecasts Key Concepts • What instruments are What do you think? Read the two statements below and decide used to measure weather whether you agree or disagree with them. Place an A in the Before column variables? if you agree with the statement or a D if you disagree. After you’ve read • How are computer models this lesson, reread the statements to see if you have changed your mind. used to predict the Before Statement After weather? 5. Weather variables are measured every day at locations around the world. 6. Modern weather forecasts are done using computers. 3TUDY#OACH K-W-L Divide a sheet of Measuring the Weather paper into three columns. In The first step in making a weather forecast is to measure the first column, write what the conditions of the atmosphere. You learned in Lesson 1 you know about weather that a variety of instruments is used to measure weather forecasts. In the second variables. A thermometer measures temperature. A barometer column, write what you want measures air pressure. A psychrometer measures relative to know about weather forecasts. Fill in the third humidity, and an anemometer measures wind speed. column with facts you Meteorologists use the data from these instruments to make learned about weather weather forecasts. forecasts after you have Surface and Upper-Air Reports read this lesson. A surface report describes a set of weather measurements made on Earth’s surface. Weather variables are measured by a weather station. A weather station is a collection of instruments that report temperature, air pressure, humidity, precipitation, and wind speed and direction. Cloud amounts and visibility are often measured by human observers. 1. Relate How does a weather balloon assist with An upper-air report describes wind, temperature, and humidity radiosonde reports? conditions above Earth’s surface. These atmospheric conditions Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. The McGraw-Hill of a division © Glencoe/McGraw-Hill, Copyright are measured by a radiosonde (RAY dee oh sahnd). A radiosonde is a package of weather instruments carried high above ground by a weather balloon. Radiosonde reports are made twice daily, all at the same time, at hundreds of locations around the world. Reading Essentials Weather 223 CC173_015_018_RE_L3_889407.indd173_015_018_RE_L3_889407.indd 1155 22/19/10/19/10 33:21:51:21:51 PPMM Satellite and Radar Images Images taken from satellites orbiting at 35,000 km above Make a two-tab book, Earth provide information about weather conditions on and then use it to collect Earth. A visible light image shows white clouds over Earth. information on satellite and radar images. An infrared satellite image shows infrared energy in a false color. The infrared energy comes from Earth. It is stored in the atmosphere as latent heat. Monitoring infrared energy Weather Doppler Satellites Radar provides information about cloud height and atmospheric temperature. Meteorologists use these satellite images to identify fronts and air masses. Radar measures precipitation when radio waves bounce off raindrops and snowflakes. Doppler radar is a specialized type Key Concept Check of radar that can detect precipitation as well as the movement of small 2. Identify the weather particles, which can be used to approximate wind speed. Wind causes variables that radiosondes, the movement of precipitation. Thus, Doppler radar can be infrared satellites, and used to estimate wind speed. Measuring wind speed is Doppler radar measure. especially important during severe weather, such as tornadoes or thunderstorms. Weather Maps Every day, thousands of surface reports, upper-air reports, and satellite and radar observations are made around the world. Meteorologists have tools that help them understand Visual Check the large amount of weather data collected. 3. Name two weather The Station Model variable measurements Companies, Inc. The McGraw-Hill of a division © Glencoe/McGraw-Hill, Copyright The figure below shows the station model. The station included on the station model. model diagram displays data from many different weather measurements for one location. It uses numbers and symbols, and it displays all observations from surface reports and upper-air reports. The Station Model Temperature (°F) Barometric pressure coded Type of 76 194 Change in pressure precipitation 70 +2 (in tenths of millibars) Dew point Wind speed 76 194 70 +2 temperature and direction Richmond VIRGINIA 224 Weather Reading Essentials CC173_015_018_RE_L3_889407.indd173_015_018_RE_L3_889407.indd 1166 22/19/10/19/10 33:21:55:21:55 PPMM Mapping Temperature and Pressure Weather maps use more symbols than the station model. For example, weather maps show isobars. Isobars are lines that connect all places on a map where pressure has the same value. Find an isobar on the map below. Isobars show the location of high-pressure and low-pressure systems. Isobars also give information about wind speed. Winds are strong when isobars are close together. Winds are weaker when isobars are farther apart. In a similar way, isotherms (not shown on the map below) are lines that connect places with the same temperature. Isotherms show which areas are warm and which are cold. Lines with symbols on them show fronts. Look at the map below to see the symbols used for different types of fronts. Reading Check 4. Compare isobars and Weather Map isotherms. isobar A 1004 1020 H 10 -2 1000 H 28 1024 L KEY 28** 25 Cold front ** Warm front 25 Stationary front 34 23 Occluded front 34 18 20 Precipitation 6 * * Light snow 58 Light rain 49 59 H High-pressure system 50 1016 L Low-pressure system Wind direction (N) H Visual Check Wind speed (20 knots) 22 Air temperature 22°F 5. Identify Which symbols 15 Dew point 15°F represent high-pressure and low-pressure systems? Predicting the Weather Meteorologists use computer models to help them forecast the weather. Computer models are detailed computer programs that solve a set of complex mathematical formulas. The formulas predict what temperatures and winds might occur, when and where it will rain or snow, and what types of clouds will form. Key Concept Check Government meteorological offices use computers and 6. Describe How are the Internet to share weather measurements throughout the computers used to predict day. Weather maps are drawn and forecasts are made using the weather? Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. The McGraw-Hill of a division © Glencoe/McGraw-Hill, Copyright computer models. The maps and forecasts are made available to the public through television, radio, newspapers, and the Internet. Reading Essentials Weather 225 CC173_015_018_RE_L3_889407.indd173_015_018_RE_L3_889407.indd 1177 22/19/10/19/10 33:22:06:22:06 PPMM Mini Glossary computer model: a detailed computer program that solves isobar: a line that connects all places on a map where pressure a set of complex mathematical formulas has the same value Doppler radar: a specialized type of radar that can detect surface report: a set of weather measurements made on precipitation as well as the movement of small particles, Earth’s surface which can be used to approximate wind speed upper-air report: a description of wind, temperature, and humidity conditions above Earth’s surface 1. Review the terms and their definitions in the Mini Glossary. Write a sentence that compares and contrasts a surface report and an upper-air report. 2. In the station model below, identify the measurements that were made by a barometer, a thermometer, and an anemometer. Write the name of the instrument in the blank next to its measurement. a. ______________________ b. ______________________ Temperature (°F) Barometric pressure coded Type of 76 194 Change in pressure Companies, Inc. The McGraw-Hill of a division © Glencoe/McGraw-Hill, Copyright precipitation 70 +2 (in tenths of millibars) Dew point Wind speed temperature and direction c. ______________________ 3. What is infrared energy and how does an infrared satellite image display it? What do you think Reread the statements at the beginning of the ConnectED lesson. Fill in the After column with an A if you Log on to ConnectED.mcgraw-hill.com agree with the statement or a D if you disagree. and access your textbook to find this END OF Did you change your mind? lesson’s resources. LESSON 226 Weather Reading Essentials CC173_015_018_RE_L3_889407.indd173_015_018_RE_L3_889407.indd 1188 22/19/10/19/10 33:22:14:22:14 PPMM Name Date Class Content Vocabulary LESSON 3 Weather Forecasts Directions: On each line, write the term from the word bank that correctly replaces the underlined words in each sentence. NOTE: You may need to change a term to its plural form. computer model Doppler radar isobar surface report upper-air report 1. Tornadoes and thunderstorms, as well as other types of weather, can be tracked using a special system of measurement that can detect precipitation and can estimate wind speed. 2. On a weather map, high- and low-pressure systems are indicated by lines that connect all places where pressure is the same. 3. Weather forecasts use information from sets of mathematical formulas calculated by computer programs. 4. Information gathered by a weather station and by human observers is used to put Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. The McGraw-Hill of a division © Glencoe/McGraw-Hill, Copyright together a(n) summary of weather measurements on Earth’s surface. 5. A(n) summary of weather conditions above Earth’s surface is based on measurements made by a weather balloon. 48 Weather CC173_047_052_CRF_L3_891446.indd173_047_052_CRF_L3_891446.indd 4488 110/5/090/5/09 44:17:11:17:11 PPMM Name Date Class Lesson Outline LESSON 3 Weather Forecasts A. Measuring the Weather 1. Meteorologists measure before making a forecast.