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Fig. 2 | Movement Ecology

Fig. 2

From: Flight speed and performance of the wandering albatross with respect to wind

Fig. 2

Vectoral decomposition of wind, air and ground velocities. Unbroken arrows indicate true vectors, while dashed lines indicate vectoral components parallel air and ground velocity. All speeds are in m/s. In this example, a 4.0 m/s uniform wind blowing toward the bottom of the figure (southward) would advect a bird downwind at 4 m/s as it flies at 12.0 m/s on a heading of 45 degrees relative to the downwind direction. The bird’s ground velocity (velocity over the ground) is the vector sum of air velocity (velocity of the bird through the air) and wind velocity. The resulting ground velocity would be 15.1 m/s at an angle of 34 degrees relative to the wind velocity. If both the ground velocity of a bird and the wind velocity were measured one could calculate the bird’s air velocity by subtracting wind velocity from ground velocity. Because an albatross soars through the wind-shear boundary layer, estimating downwind advection velocity is more complicated than simply using the wind velocity at the average height of the bird (see Methods). We refer to the downwind advection velocity by the wind as “leeway velocity,” which we estimate from the wind and flight data. In this study leeway velocity is around one half of the wind velocity at our chosen reference height of 5 m.downwinddownwinddownwind

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