Wind

Reference ACWM Chapters 5 and 11

Wind is the result of changes in pressure gradient.

• flows from High to Low 
• steeper gradient = stronger wind

Coriolis Effect

• the deflection of wind caused by the Earth's rotation
• varies from zero at equator to maximum strength at poles

Curvature Effect

• when isobars are curved, air moves in an arc >> centrifugal force
• the pressure gradient around lows is generally stronger than around highs

Friction

• As you climb from the surface to 3000 feet, the wind veers (clockwise change in direction) and increases.
• As you descend from 3000 feet to the surface, the wind backs (counterclockwise change in direction) and decreases.
• We must also keep in mind that land and water create different amounts of friction.  There is less friction over water, so wind would blow at less of an angle across isobars and at faster speeds. 

Squalls and Gusts

• characteristics of turbulent flight conditions
• Gusts >> rapid peaks and lulls
• Squalls >> sudden increase lasting for a minute or more, then a decrease

Diurnal Effects

• surface winds are usually stronger and gustier during the day
• Sea Breeze during the day (higher pressure over water than land)
• Land Breeze at night

Topographical Effects

• hilly and mountainous terrain can contribute to mechanical turbulence
• Anabatic winds flow upslope during the day when mountain slops facing the sun are heated
• Katabatic winds flow downslope
• warm = Chinook wind, warms at DALR
• cold = glacier wind, cooling by underlying ice

Wind Shear

• increased performance (headwind) >> airspeed increases
• encountering increased performance on glideslope >> would have to reduce power to recapture glidepath, then increase power to maintain due to stronger headwind
• decreased performance (tailwind) >> airspeed decreases