8.12 Wind

8.12.2 Define the measurement of the standard surface wind in aviation meteorological reports and forecasts.

Surface wind is measured by an anemometer (speed) or wind vane (wind direction) at a standard height of 10 m above ground in order to avoid the influence of eddies.

8.12.4 State the units used to describe wind speed.

To indicate wind speed in NZ aviation we use knots (kts).

8.12.6 State the units used to describe wind direction with reference to:

Wind is described in terms of the direction from which it blows, and is given as compass-point expressions graduated into 360 degree directions clockwise from north.

(a) forecasts and observations issued by MetService;

All forecasts and observations issued by MetService are given in degrees True.

(b) spot winds relayed to pilots by Air Traffic Control.

Spot winds relayed by Air Traffic Control either verbally or on the ATIS are given in degrees Magnetic.  

8.12.8 List the three forces acting to generate wind at low-levels.

The 3 forces which influence the wind strength and direction are:

• Coriolis Force
• Pressure Gradient; and
• Friction Forces.

8.12.10 Outline the cause of Coriolis force.

The Coriolis force is an effect created by the rotation of the Earth.