Radar bounces radio waves off water particles in clouds.
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Radar is important to weather forecasters because it can detect rain and hail. The radar bounces radio waves off water particles in clouds. A computer measures how long it takes for the radio waves to reflect back and then uses the time to calculate how far the particle is from the radar. It also measures how much energy is reflected back to the radar, which lets us know how much precipitation is in the clouds.
A new kind of radar called Doppler radar can do a lot more. In addition to showing how far away a raindrop is, Doppler radar can also calculate if that raindrop is moving toward or away from the radar. Meteorologists know that if the rain is moving, wind must be pushing it. This is how they know where the wind is blowing in the clouds.
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