Parameter Tree:
EARTH SCIENCE > ATMOSPHERE > ATMOSPHERIC WINDS > SURFACE WINDS > WIND SPEED

Definition:
Ratio of the distance covered by the air to the time taken to cover it. The instantaneous speed corresponds to the case of an infinitely small time interval. The mean speed corresponds to the case of a finite time interval. It is one component of wind velocity, the other being wind direction).

Reference:
Glossary of Meteorology, American Meteorological Society