Don't know why this is being downvoted. It's important for scientists to use the correct, well-established terms when discussing their research. This is most true for formal publications.
Velocity is a vector quantity--it describes a directional rate of change. Speed is the magnitude of the velocity. When they use the term velocity, they mean speed. For example, even in the abstract:
"along trajectories determined by the direction and velocity of the wind"
Velocity has a direction! The use of direction in this sentence is redundant to anyone that has had a college level physics course. This trend of using "velocity" instead of "speed" continues through the entire paper. I find this very upsetting.
Of course, it may seem pedantic, but good science is pedantic.
I'm surprised that it made it through peer-review like this.
