Lesson: Weather ForecastingContributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Educational Standards :
Learning Objectives (Return to Contents)
After this lesson, students should be able to:
Introduction/Motivation (Return to Contents)
What were you thinking about when you dressed for school this morning? Specifically, how did you decide what to wear today? Did you glance out the window to see what the weather was doing? If you looked out the window, what were your clues? (Possible answers: Clouds, sunshine, wind blowing through the trees, birds in the sky, etc.) So, without even thinking about it this morning, you were forecasting the weather! In the same way, people around the world have been forecasting the weather for thousands of years. For a long time, people relied on weather patterns to predict the weather. Who has heard the following expression?
"Red skies in the morning, sailors take warning? Red skies at night, sailors' delight."
Well, although this rhyme is not entirely true, ancient sailors used it as a rule of thumb, due to the fact that a red morning sun did indeed often bring rain (because the red sky occurred when the air was full of dust and water vapor).
Besides sailors navigating on the open water and you wanting to dress right for the weather, why do we care about weather forecasting? (Note: Show students the weather section of the day's newspaper.) Why is there a weather section in the newspaper? When you do see people consulting the weather forecast, either in the newspaper or on television? (Possible answers: Before planning a trip, a sporting event, going on a picnic, doing outside chores, etc.) What about people who grow food? Do any of you have a garden at your house? It is certainly helpful to understand the weather when taking care of a garden.
For farmers, whose crops are their livelihood, the ability to predict the weather is crucial. Before the advent of modern weather forecasting technology, which we will discuss later, how do you think farmers predicted the weather? (Note: If possible, show the students a copy of the Farmer's Almanac.) Some of you may have heard of The Farmer's Almanac, a book — used since 1792 — that uses a complex series of natural cycles to devise a secret weather forecasting formula, traditionally said to be 80% accurate. Before modern weather technology, farmers relied heavily on the Almanac to plan their crop growing seasons. People around the country still read the Almanac to learn about farming, the weather and to understand astronomical events and ocean tides (see Additional Multimedia Support section for a website link to a Farmer's Almanac video).
How do you think people forecast the weather today? (Possible answers: Satellites, weather balloons, computers.) During the past 100 years, engineers and scientists have worked to design modern forecasting equipment such as weather balloons, satellites, Doppler radars and more to help predict the weather. Fortunately, modern equipment has made it much easier to predict weather, climate and water-related hazards around the world, which account for nearly 90% of all natural disasters. Modern weather forecasting technology provides vital information for advance warnings of natural disasters such as tornadoes, hurricanes and floods. Improved technology has saved many lives and reduced damage to property and the environment.
Lesson Background & Concepts for Teachers (Return to Contents)
History of Weather Forecasting
Humans have always attempted to predict the weather. In 650 BC, people living in Babylonia, an ancient state in the southern part of Mesopotamia (modern day Iraq), predicted the weather from cloud patterns. The ancient Chinese predicted the weather by observing patterns of events. If the sunset was unusually red, it was often an indication of good weather for the following day. Although these ancient methods of weather forecasting were used for centuries, they were not always reliable. Another limitation was that information about the current state of the weather could not be communicated to places far away. So, if a community of Babylonians were experiencing a terrible storm, they had no way to warn their neighbors downwind that trouble was coming!
The most basic weather forecasting is still based on the observation of weather patterns, which over the years has led to folklore about the weather (see the Pre-Lesson Assessment section). You are probably familiar with Groundhog Day, celebrated on February 2 in the US. This folklore originated from ancient Celtic people who believed that if the winter's midpoint was sunny and clear, a long, cold winter would follow. Today, people celebrate this day with a groundhog named Punxsutawney Phil, who resides in Philadelphia. The tradition is that every year, on the morning of February 2, Punxsutawney Phil leaves his home under the ground. If it is sunny and clear enough for little Punxsutawney Phil to "see his shadow," a long winter is predicted. Unfortunately, this weather folklore is only accurate about half the time!
Modern Forecasting Equipment
Today, we rely on modern forecasting technology and engineering to predict weather patterns. The modern age of weather forecasting began with the invention of the telegraph in 1837, which allowed forecasts to be made by knowing the actual weather conditions in distant places.
Even more progress was achieved during the 20th century when engineers and scientists designed computers to make numerical weather predictions (computer simulations) of the atmosphere (see Figure 2). These simulations take information about the present weather and use the computational tools of physics and fluid dynamics to predict future atmospheric states. Basically, the complicated equations used by the computer project how the working fluids of the atmosphere (that is, wind and water) are expected to change with different atmospheric conditions (that is, temperature, humidity and pressure).
It is important to note that before any fancy computer simulations can be made, "raw" weather data (actual weather measurements) must be collected.
Weathers balloons carry instruments high up into the atmosphere. The balloons, launched every day all over the world, carry a radiosonde high up into the atmosphere. The radiosonde is a small, battery powered device that collects information about atmospheric pressure, humidity, and temperature. These data are then transmitted to a ground antenna via specific radio frequencies. Wind speed and direction are calculated by tracking the weather balloon using GPS or radio direction finding. The flight of a weather balloon doesn't last very long. The weather balloon is filled with either helium or hydrogen, which lifts the device into the atmosphere at a rate of about 1000 feet per minute. In its flight, the weather balloon can ascend to over 35 km (115,000 feet) and drift more than 300 km (about 180 miles) from where it was launched. As the balloon ascends, the pressure decreases, which causes the balloon to expand from an initial diameter of 1.5 feet to 6-8 feet. Eventually the balloon expands so much that it ruptures. The radiosonde has a parachute attached to it so that it is less likely to cause damage when it returns to earth. Most radiosondes are not found after they return to earth. Of the approximately 70,000 radiosondes deployed every year, only about 20% are found and returned to the National Weather Service for reconditioning and reuse.
What about the big picture? Weather satellites are another engineering marvel that enable us to see what the Earth and clouds look like from space and give us a more comprehensive view of Earth's interrelated systems and climate. Figure 4 was created using data from four different satellites. The red dots you see are fires burning on land areas, and the large aerosol clouds over the Atlantic Ocean are from the burning of biomass in Africa. You can also see dust and clouds wrapped around the planet.
What if we wanted to see inside a large cloud or storm to analyze its structure and gauge its potential to cause severe weather? Is this possible? Military radar operators asked this same question during World War II, when they noticed noise in returned radar echoes due to weather elements such as rain, snow and sleet. When the war was over, many of these military radar operators became engineers to develop a use for the noisy echoes. Now, we have weather radar, a special type of radar that uses radio waves to "see" how precipitation is behaving in a cloud and how it might change.
RADAR stands for radio detection and ranging. Basically, a radar is an electronic instrument used to determine the direction and distance of objects that reflect radio energy back to the radar site. Weather radars use radio waves to locate precipitation and determine its type (rain, snow, sleet or hail). They also calculate the motion of precipitation and forecast its future position and intensity.
All weather radars work by the process of scattering, in which radiation energy is reflected by small particles, as shown in Figure 5. So, when weather radar sends a radar beam out into space, the precipitation particles in the atmosphere cause the radiation energy to scatter. The motion and behavior of the scattered radiation is read by the radar site and translated into important weather information.
The Doppler Radar
Most weather radars are Doppler radars, which can also detect the motion of rain droplets. Doppler radar gets its name from the Doppler effect. Have you ever listened to an ambulance siren or a train whistle as it was coming toward you? You probably noticed that the pitch of the whistle changed as the train passed you and moved away. This change in the frequency of sound is called the Doppler effect.
A Doppler radar measures the changes in the frequency of the signal it receives to detect the intensity of precipitation, estimate wind direction and speed, and predict hail size and rainfall amounts. Doppler radar gives forecasters the capability of providing early detection of severe thunderstorms that may bring strong damaging winds, large hail, heavy rain and possibly tornadoes. Figure 7 shows the radar reflectivity image of the Oklahoma City/Twin Lakes Doppler radar taken on May 8, 2003, just before a tornado hit the General Motors plant in the area. Because the Doppler radar (shown is the early formation of the tornado) provided the NOAA National Weather Service with 30 minutes advance warning, officials were able to move the 1,200 employees to a shelter before the tornado hit.
Who Uses the Information?
We can certainly appreciate the staggering advances in weather forecasting equipment since the telegraph was used 100 years ago. What about the people who use the equipment? Who looks at all this weather data? Who checks to see if it makes sense?
One international organization is the World Meteorological Organization (WMO), an agency of the United Nations. WMO works to verify and standardize weather data and make it available to national meteorologists, local forecasters and other people interested in weather science and forecasting. This weather data is then put into maps by computers, which can make forecasts based on certain conditions and mark them on weather maps. Then, it is the meteorologist's job to read and interpret these maps to make forecasts about the weather. You can obtain daily weather information for your city from the World Meteorological Organization by visiting http://worldweather.wmo.int/.
It is interesting to note that, according to NASA, the US statistically has the world's most violent weather. In a typical year, the US endures about 10,000 violent thunderstorms, 5,000 floods, 1,000 tornadoes, and several hurricanes. For this reason, improving weather prediction has been a high priority of meteorologists for a very long time. Engineers and scientists continue to work to improve weather forecasting technology to provide more accurate weather forecasts for the benefit of society, the economy and the environment.
Vocabulary/Definitions (Return to Contents)
Associated Activities (Return to Contents)
Lesson Closure (Return to Contents)
Now that we have learned how weather forecasting has come a long way from the basic observation of weather patterns, we can appreciate the work of engineers who have worked so hard to develop modern forecasting equipment. Advanced technology such as weather balloons, satellites and Doppler radars have improved the quality of people's lives around the world by helping us plan our days, plant our crops, and prepare for natural hazards, such as hurricanes, tornadoes and floods.
Attachments (Return to Contents)
Assessment (Return to Contents)
Weather Proverbs: Read the following list of weather proverbs to students. In small groups or as a class, try to guess what each weather proverb means and what it might tell us about the weather.
Worksheet: Before the introduction, give each student a copy of the attached Cool Weather Forecasting Facts Worksheet. Have students take notes while listening to the introduction and lesson (using the information from the Lesson Background section). At the end of the lesson, have students share their cool weather forecasting facts with the class. This worksheet can also be used as a lesson organizer.
Lesson Summary Assessment
Explaining Weather Proverbs: Return to the list of weather proverbs listed in the Pre-Lesson Assessment. Now have students explain how they could test these proverbs. What forecasting equipment might students use to determine if the proverbs are true?
Lesson Extension Activities (Return to Contents)
Understanding the Doppler Effect: Conduct the following demonstration to show students how the Doppler effect works and how Doppler radar helps meteorologists predict the weather.
You will need:
Explanation: The change in the frequency of sound is called the Doppler effect. Doppler radar measures the changes in the frequency of the signal it receives to detect the intensity of precipitation, estimate wind direction and speed, and predict hail size and rainfall amounts.
Additional Multimedia Support (Return to Contents)
Hands-on weather experiments for kids, http://www.srh.noaa.gov/bmx/?n=kidscorner_weatherexperiments
Farmer's almanac website with activities, videos and long-range weather forecasts, http://www.farmersalmanac.com.
References (Return to Contents)
Annenberg Media, Learner.org, Interactives: Weather, "Forecasting," accessed December 12, 2007. http://www.learner.org/exhibits/weather/forecasting.html
Farmer's Almanac, accessed December 14, 2007. http://www.farmersalmanac.com
NASA Ames Research Center, Flight Desk Display Research Laboratory, Implementations, "3D Cockpit Situation Display (CSD)," accessed December 12, 2007. http://human-factors.arc.nasa.gov/groups/FDDRL/technologies/3dcdti.php
National Weather Service Forecast Office, El Paso Office, Kid's Weather, "Experiments," accessed December 14, 2007. http://www.srh.noaa.gov/bmx/?n=kidscorner_weatherexperiments
National Aeronautics and Space Administration, SP-4312 Dreams, Hopes, Realities, "Chapter 5: Exploring the Earth," accessed December 14, 2007. http://history.nasa.gov/SP-4312/ch5.htm
National Oceanic and Atmospheric Administration, accessed December 14, 2007. http://www.crh.noaa.gov/fsd/science/doppler/images/scat.gif
National Oceanic and Atmospheric Administration, accessed August 13, 2014. Radiosonde Observations. http://www.ua.nws.noaa.gov/factsheet.htm
Tarp, Keli. National Oceanic and Atmospheric Administration, "NOAA Provides Expertise For Development Of New Radar Network," accessed December 14, 2007. http://www.noaanews.noaa.gov/stories/s2097.htm
ContributorsLauren Cooper, Malinda Schaefer Zarske, Janet Yowell
Copyright© 2007 by Regents of the University of Colorado.
Supporting Program (Return to Contents)Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Acknowledgements (Return to Contents)
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.