What does a meteorologist need before he or she can forecast the weather?
Data! A meteorologist needs data about the current conditions. There are many types of instruments available for collecting that data. According to the World Meteorological Organization (WMO), a 5-day weather forecast today is as reliable as a 2-day forecast was 20 years ago.
Predicting the Weather
Weather is very difficult to predict. That’s because it’s very complex, and many factors are involved. Slight changes in even one factor can cause a big change in the weather. Still, certain “rules of thumb” generally apply. These “rules” help meteorologists forecast the weather. For example, low pressure is likely to bring stormy weather. So if a center of low pressure is moving your way, you can expect a storm.
People often complain when the weather forecast is wrong. Weather forecasts today, however, are much more accurate than they were just 20 years ago. Scientists who study and forecast the weather are called meteorologists. How do they predict the weather?
The first thing they need is data. Their data comes from various instruments.
Weather instruments measure weather conditions. One of the most important conditions is air pressure, which is measured with a barometer ( Figure below ). There are also a number of other commonly used weather instruments ( Figure below ):
- A thermometer measures temperature.
- An anemometer measures wind speed.
- A rain gauge measures the amount of rain.
- A hygrometer measures humidity.
- A wind vane shows wind direction.
- A snow gauge measures the amount of snow.
The greater the air pressure outside the tube, the higher the mercury rises inside the tube. Mercury can rise in the tube, because there’s no air pressing down on it.
Some of the most commonly used weather instruments.
Weather instruments collect data from all over the world at thousands of weather stations ( Figure below ). Many are on land, but some float in the oceans on buoys. There’s probably at least one weather station near you.
Other weather devices are needed to collect weather data in the atmosphere. They include weather balloons, satellites, and radar ( Figure below ).
Weather stations collect data on land and sea. Weather balloons, satellites, and radar collect data in the atmosphere.
Weather stations contain many instruments for measuring weather conditions. The weather balloon ( Figure above ) will rise into the atmosphere until it bursts. As it rises, it will gather weather data and send it to the surface. Many weather satellites orbit Earth. They constantly collect and transmit weather data from high above the surface. A radar device sends out radio waves in all directions. The waves bounce off water in the atmosphere and then return to the sender. The radar data shows where precipitation is falling. It’s raining in the orange-shaded area shown above.
What do meteorologists do with all that weather data? They use it in weather models. The models analyze the data and predict the weather. The models require computers. That’s because so many measurements and calculations are involved.
- anemometer : Instrument that measures wind speed.
- barometer : Instrument for measuring atmospheric pressure.
- hygrometer : Device that measures humidity.
- radar : Radio detection and ranging device that emits radio waves and receives them after they bounce on the nearest surface; this creates an image of storms and other nearby objects.
- rain gauge : Instrument that measures the amount of rain.
- snow gauge Device that measures the amount of snow.
- thermometer : Device that measures temperature.
- weather balloon : Balloon that rises into the troposphere; it gathers weather data to send back to the surface.
- weather satellite : Satellite that orbits Earth and constantly collects and transmits weather data from high above the surface.
- weather station : One of thousands of devices that collect weather data at a location on Earth's surface.
- wind vane : Device that shows wind direction.
- Various instruments measure weather conditions: thermometers measure air temperature, and barometers measure air pressure.
- Satellites monitor weather from above.
- Radar is used to monitor precipitation.
Use the resource below to answer the questions that follow.
- Predicting Weather at http://www.youtube.com/watch?v=dqpFU5SRPgY (5:52)
- Why is weather difficult to predict?
- What is the afternoon constellation? What does it do?
- What are the basic shapes of clouds?
- What is fog?
- Why is it important to study clouds?
- What will Cloudsat do? Why is this an improvement?
- What can a barometer tell you about the coming weather?
- Why is weather prediction better than it used to be?
- What is the purpose of a weather satellite?