system
Given the following post, respond as if you're commenting on Reddit:
human
How do we quantify wind speeds on gas giant planets?

I recently read that Saturn has wind speeds up to 500m/s. On Earth we measure wind speeds relative to the solid ground, but since gas giants have no solid ground how do we distinguish the speed of their winds from the rotation of the planet itself?
gpt
Saturn's rotational period (day) was originally measured using radio wave emissions. Since you have an estimate of its angular velocity, you can then calculate how fast the "planet" would be at the radius of the outer clouds. Then you get an estimate for the angular velocity of the cloud you are interested in. The difference between those two angular velocities is the angular velocity relative to the "ground". Using the radius from the core to that point, you then can find the "wind speed" in terms of linear velocity.