A simple weather radar can detect precipitation or objects just by the reflection of microwaves. Most weather radar employ pulsed microwave signals. With more precipitation or a bigger object, there is more reflectivity. As in the case with heavy rain or hail, more signal is reflected back to the radar dish.
In meteorology, the Doppler effect becomes especially useful. While Doppler radar can still detect reflectivity, other information is collected from the returning microwave signal.
That information is in the form of Doppler shift of the microwave signal. The information is then collected in real time by computer to derive wind velocity. The velocities that can be detected by a single dish are velocities that are going away from the dish or toward the dish (see vector mechanics[?]).
Even though most weather radar has the ability to collect Doppler wind velocities, it is usually not used for display to the public since it is difficult for the experienced meteorologist to quickly understand. Typically, research meteorologists depend more heavily on the Doppler data for wind vector retrieval. Also, for example, some products from Doppler data are used to indicate (on the reflectivity display) regions of wind sheer[?]. Most TV meteorologist refer to their radar products as "Doppler", when in reality their displays are just reflectivity.