| |
|
|
|
|
|
|
|
| |
|
|
| |
| |
|
|
| |
|
|
| |
People use many kinds of instruments to collect weather data. Weather forecasts are based on the data collected. |
|
| |
Collecting Data |
|
| |
What exactly is weather? How would you define it? To completely describe a weather system at any particular place and time, you need to describe all its parts: the temperature, moisture, clouds, precipitation, wind speed, air pressure, and wind direction. All of these parts may interact with each other and change during the course of a day. They may change even more quickly than that! |
|
| |
Many kinds of tools measure all these parts of the weather. Some of these instruments might even be in your home. What weather-measuring tool have you used that is not shown here? |
|
| |
A barometer shows air pressure. In some barometers, air pressure pushes mercury up a tube. The barometer shown here has a small sealed container connected to the dial. When air pressure squeezes on the container, it causes the dial of the barometer to move. |
|
| |
An anemometer measures wind speed. The wind makes the cups of the anemometer spin around. Cups spin faster as winds move faster. A hygrometer measures the moisture in the air. Some hygrometers have a pointer attached to horsehair. The hair shortens in drier air, moving the pointer. |
|
|
|
| |
|
|
| |
|
|
|
|
| |
|
|
| |
|
|
| |
|