Final answer:
To identify a landspout circulation, radar radial velocity data is best as it can detect the rotational velocity of rain droplets associated with this weak tornado phenomenon.
Step-by-step explanation:
The best data to identify a landspout circulation would be (c) radar radial velocity. Landspouts are a type of tornado that does not arise from a supercell thunderstorm. They are more similar to waterspouts but occur over land, featuring relatively weak circulations that are often not detected by radar reflectivity.
However, radar radial velocity data can detect the motion of rain droplets within the storm and provide information about the rotational velocity of the weather system. Therefore, this type of radar imagery can reveal the signatures of rotation associated with landspout formations.