While a single wind turbine is unlikely to confuse a radar return signal, a wind farm, particularly one 20 square miles or larger, will pose a problem. For example, the radar returns from the weather radar in Sullivan continually measures what looks to be a rain cloud to the north. This signal is always there and is the location of a wind farm.
A radar consists of a transmitter and a receiver. The transmitter emits pulses of radiowaves outward in a circular pattern. Precipitation scatters these radiowaves, sending some energy back to the transmitting point where it is detected by the radar’s receiver as a radar return signal. The wind turbine towers are made of metal and have a strong radar return signal and will appear as a fixed object in a radar image. Many of the rotating blades are made of materials transparent to radar, but they often have metal lightning ground wires running through each blade — increasing the radar signature. The various speeds of the different turbines can modulate the radar return, so the radar image will continually change.
There are ways to get around to this problem, ranging in expense. Perhaps the simplest is to know that the farm is there and thus recognize that when it exists in an isolated manner that it is not raining.
Wind farms can also show up on surveillance radar used for aviation airspace control, which perhaps poses a more serious problem. As the number of wind farms continues to increase, their impact on radar is important to understand.