Reference From the Ground Up Chapter 6.4: Winds Pages 130 - 136
Introduction • Wind is the horizontal movement of air in different areas and altitudes. • It is important that pilots know where winds are, how strong and from what direction they flow, and how they change.
Outline • Wind Types • Wind Speed and Direction • Wind Effects
Winds • Wind is horizontal movement of air • Heating of Earth creates pressure differences, air flows from high to low, therefore wind • Upper Level Winds flow parallel to isobars and from high to low pressure areas • Surface Winds are below 3000 ft, and are slowed by surface friction
Land & Sea Breezes • Sea Breeze • Land heats faster than water during day (lower pressure) • Wind blows from water towards land
Land & Sea Breezes • Land Breeze • Land cools faster than water at night (higher pressure) • Wind blows from land towards water
Mountain Winds • Katabatic Wind (AKA Mountain Breeze) • At night, slope cools, air becomes denser, wind flows down from mountain
Mountain Winds • Anabatic Wind (AKA Valley Breeze) • During day, slope heats, air becomes less dense, flows up from valley
Mountain Winds • Mountain Wave • Air deflected after flowing over mountain oscillates (or bounces) up and down violently in a wave pattern.
Gusts and Squalls • Gust • Sudden and brief increase in wind speed and direction (several seconds) • Usually caused by mechanical turbulence • Squall • Sudden increase in wind speed and direction, but last longer then a gust (several minutes) • Usually caused by fast moving cold front or thunderstorm
Wind Speed & Direction • Veering is increase in wind direction • Backing is decrease in wind direction • Wind veers and increases with altitude (due to lack of surface friction) • Diurnal Variation • Wind backs and decreases at night • Wind veers and increases during day (more ground heating)
Wind Effects • Eddies • Swirling air or vortices • Produced by friction between moving air and ground
Wind Effects • Dust Devils • Super-heated concentrated lows on hot, clear, stable, days • Made visible by dust or sand
Wind Effects • Tornadoes • Very concentrated, violent lows formed in unstable weather
Wind Effects • Jet Stream • Narrow bands of high-altitude and high-speed winds • Normally 2 or 3 over North America
Next Lesson 4.5 – Meteorology Humidity, Temperature & Stability From the Ground Up Chapter 6.5: Humidity, Temperature and Stability Pages 136 - 140