LESSON 5 - ACTIVITY 6 - WEATHER SATELLITES, SATELLITE IMAGES, AND DOPPLER RADAR
Materials
Background Information
Key Questions
Vocabulary
Procedure
Evaluation
Objectives
- Define weather satellites.
- Explain the role of weather satellites to weather forecasting.
- Describe the two types of weather satellites.
- Explain the difference between a visible satellite image and an infrared satellite image.
- Explain how a radar echo works.
- Investigate doppler radar.
Materials
- globe
- black and white construction paper
- thermometers
- tennis ball
Background Information
A weather satellite monitors the weather and climate of the Earth. These meteorological satellites detect more than just clouds & cloud systems. They can detect and monitor city lights, pollution, fires, the northern or southern lights, snow cover, dust storms, ocean currents, icebergs, and energy waste.
Weather satellite images assisted with the monitoring of the volcanic ash cloud when Mount St. Helens erupted and monitored activity from Mount Etna as well as tracked smoke from wildfires in the western US. They are able to track El Niņo and monitor its effects on weather.
There are two types of meteorological satellites, geostationary and polar orbiting.
Geostationary weather satellites are located nearly 22,300 miles over the equator. Because of their orbit path, they follow the Earth's rotation and can record and transmit pictures of an entire hemisphere. The news and weather media use the photos taken by geostationary satellites to produce their weather forecasts.
Geostationary Satellite Image NOAA
Several geostationary satellites are in orbit. The US has three geostationary satellites in orbit; GOES-9, 10 and 12. The geostationary satellites GOES-12 is known as GOES-East and is situated above the Amazon River. It supplies the US with most of its weather data. GOES-10, known as GOES-West, is situated over the eastern Pacific region. GOES-9 has been loaned to Japan and is situated over the Pacific ocean. The Europeans geostationary satellites are METEOSAT-6, 7 and 8 and are situated over the Atlantic Ocean as well as METEOSAT-5 situated over the Indian Ocean. Russia operates the GOMS situated above the equator just south of Moscow. China and India also operate geostationary satellites.
Polar orbiting meteorological satellites orbit the Earth around 500 miles high and travel in a north/south path & pass over both poles in their flight. Polar satellites are able to monitor any location on Earth and views every location two times a day. These satellites travel with the path of the sun so all images produced have about the same lighting.
Polar orbiting satellite image NOAA
Visible images: Satellites measure the sunlight that is reflected by clouds and the Earth's surface. Water absorbs sunlight and reflects very little so water shows up as dark spots on the image. The amount of sunlight that is reflected by land is called surface albedo. The albedo of land is usually around 10-30%, unless the land is covered with snow which generates a much higher albedo. Cloud's have a high albedo which varies depending on the composition and thickness of the clouds. Thick clouds produce a high albedo and will show up very white on a satellite image. Cirrus clouds, which are thin, produce a low albedo and show up as semi-transparent areas. Cloud structure in a satellite image tell a meteorologist a lot of information about weather and when the images are set in motion, helps to understand which way a weather pattern is moving.
Visible Satellite Image Unisys
Infrared imagery: Satellites also measure cloud and surface temperature by using an infrared sensor. Meteorologists can detect changes in cloud temperature and the daytime and nighttime temperatures of the surface of the Earth. Clouds are generally colder than the water or land. Cloud temperature can also tell the meteorolgist how tall the clouds are because the taller the cloud, the cooler the temperature. When meteorologists examine the infrared data, they color warm clouds gray, cool clouds white, and very cold clouds a brighter white. Meteorologists also color code infrared data so they can interpret the data more easily. Colder clouds are more likely to produce rain. The temperature of clouds also lets the meteorologist know how hard it is raining and if the storm is producing severe weather. The satellite measures surface temperature in areas that have no cloud cover. In an infrared image, warmer temperatures are dark in color and colder temperatures are light in color. Arid regions, such as deserts, are hot and show up as dark on the image, whereas areas at higher elevations are cooler and show up brighter on the image. Infrared images are also used to measure sea-surface temperature. Around 70% of the Earth is covered by water, scientists use satellite and infrared data to study how sea-surface temperature changes affect weather events like El Nino hurricanes, droughts, and flooding.
Infrared Satellite Image Unisys
RADAR stands for Radio Detection and Ranging. A radar echo is an electronic signal that has been reflected back to the radar antenna and is used to determine location and distance. This is very useful in the detection of rain and snow.
The radar shoots out a short, high-intensity burst of high-frequency radio waves. The radar then turns off its transmitter, turns on its receiver and listens for an echo. The radar measures the time it takes for the echo to return. If the radar detects precipitation, the radar echo helps the meteorologist determine how far away the precipitation is as well as the speed and direction it is moving. The meteorologist can now track the storm.
Weather radar can convert areas of precipitation into colors that represent the intensity of the precipitation. There is no standard for the colors used to represent the intensity of precipitation, but areas of light precipitation is usually represented by blue or green, and areas of heavy precipitation are usually represented by yellow or red. The colors help a meteorologist determine the amount of rainfall to expect in a given period of time and helps them to make accurate forecasts.
Weather Radar Image Color weather.com
Doppler Radar is another type of weather radar. Doppler Radar has the ability to detect wind circulation and precipitation within a cloud. The ability to detect wind circulation in clouds help meteorologists determine if conditions are right for the development of a tornado. Doppler radar calculates wind direction by determining if particles are moving away or toward the radar by detecting a change in the radar signal.
Key Questions
- What is a weather satellite?
- How do meteorologists use weather satellite images to forecast the weather?
- Describe the two types of weather satellites?
Vocabulary
- satellite
- stationary satellite
- polar satellite
- satellite image
- visible satellite image
- infrared satellite image
- radar echo
- Doppler Radar
Procedure
1. Demonstrate the two different types of satellites by using a globe and your fist. Rotate your fist around the earth from the North Pole to the South Pole. Explain that this type of satellite is the Polar Orbiting Satellite. It orbits the earth once every 100 minutes by traveling from pole to pole. In other words, it is not stationed above any particular location. Next, place your fist over a specific location on the globe. As you turn the globe, keep your fist over the same location. Explain that this type of satellite is a Geostationary Satellite. This type of satellite orbits the earth at the same speed that the earth rotates which provides a continuous view of a specific location.
2. Have your students use their weather maps and according to the sky data plotted determine areas of cloud cover that would show up on a satellite image.
3. This activity will demonstrate the reflective properties and heat absorption/radiation properties of certain colors. The purpose of this activity is to demonstrate that clouds, which show up as white on a satellite image, reflect light better than dark colors. Take initial temperature readings of the black and white construction paper by placing the thermometers in the center of the papers. Next, place the black and white construction paper in direct sunlight. After approximately 10 minutes, record the new temperatures. Which color of paper recorded the highest temperature? Why was the black sheet of paper hotter than the white? This is because dark colors absorb heat and white colors reflect heat. Ask your students how this experiment relates to satellite images. Clouds reflect light, which show up as white spaces on a satellite image. The earth and large bodies of water do not reflect light and appear as dark areas on a satellite image.
4. Create an overhead transparency of the satellite image. Have your students identify areas of complete cloud coverage, scattered cloud coverage and no cloud coverage.
5. Have your class access the Internet to view satellite images of the 13 weather stations. Students will use their weather map to place a "C" over states that are experiencing cloudy weather and an S over states that are experiencing sunny weather. Have your students look for areas of cloud circulation. If any are seen, have your students place an H or an L on their weather map to label the areas as high or low pressure.
6. Ask your students if they have ever heard an echo. Explain to your students that an echo occurs when a sound or signal strikes an object and is bounced back. This is how a radar works to detect rain or snow.
You can illustrate how a radar signal works by using a tennis ball. Ask your students to imagine you are the radar, the wall is an area of precipitation, and the tennis ball is the radar signal. Stand close to a wall and throw the tennis ball at the wall and catch it as it bounces back to you. Ask your students if the storm is close or far away. Their response should be based on the amount of time it takes the tennis ball to return to you. Repeat the process at varying distances from the wall to illustrate the time it takes a signal to return to the radar determines the distance to the precipitation.
7. Allow your students to access the internet to view live radar pictures to plot incoming storms on their weather maps for the 13 weather stations. Identify areas of heavy precipitation if found. Have your students watch for the echoes from the radar. They will see the echoes as the antenna rotates and the image changes. Have your students write a summary of their findings in their journal.
Evaluation
Students will be able to describe the two types of weather satellites, explain how radar works, and interpret weather data from live radar images.
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