What does Doppler radar in weather systems primarily detect?

Doppler radar in weather systems primarily functions by measuring the velocity of precipitation, particularly rain droplets. This capability is crucial in meteorology because it allows meteorologists to determine how fast rain is moving, which in turn can provide insights into storm strength and movement.

The radar emits a signal that reflects off precipitation particles, and by analyzing the frequency shift of the returned signal—known as the Doppler effect—meteorologists can calculate the speed at which the raindrops are moving toward or away from the radar source. This information is essential for tracking severe weather patterns, predicting thunderstorms, and assessing potential flooding.

The other options, while relevant to weather forecasting, are not what Doppler radar is designed to primarily detect. Temperature fluctuations, humidity levels, and air pressure changes can be monitored through different meteorological instruments such as thermometers, hygrometers, and barometers, rather than through Doppler radar technology.