Doppler radar transmits a signal horizontally. It listens and receives this signal.
Doppler radar tracks the shape and the location of the object, such as a rain drop. It can also track the direction the object is moving. This helps us estimate wind speeds within thunderstorms and track areas of rotation.
Dual-pol radar transmits signals in both the horizontal and the vertical and is able to distinguish types of object. We can differentiate between rain and snow, and even non-meteorological objects like birds and debris. Being able to track debris with radar is crucial in confirming tornadoes.