Sep 2012 Lesson 4.4 Meteorology Winds

Reference From the Ground Up Chapter 6.4: Winds Pages

Introduction Wind is the horizontal movement of air in different areas and altitudes.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.It is important that pilots know where winds are, how strong and from what direction they flow, and how they change.

Outline Wind TypesWind Types Wind Speed and DirectionWind Speed and Direction Wind EffectsWind Effects

Winds Wind is horizontal movement of airWind is horizontal movement of air Heating of Earth creates pressure differences, air flows from high to low, therefore windHeating 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 areasUpper Level Winds flow parallel to isobars and from high to low pressure areas Surface Winds are below 3000 ft, and are slowed by surface frictionSurface Winds are below 3000 ft, and are slowed by surface friction

Land & Sea Breezes Sea BreezeSea Breeze –Land heats faster than water during day (lower pressure) –Wind blows from water towards land

Land & Sea Breezes Land BreezeLand Breeze –Land cools faster than water at night (higher pressure) –Wind blows from land towards water

Mountain Winds Katabatic Wind (AKA Mountain Breeze)Katabatic Wind (AKA Mountain Breeze) –At night, slope cools, air becomes denser, wind flows down from mountain

Mountain Winds Anabatic Wind (AKA Valley Breeze)Anabatic Wind (AKA Valley Breeze) –During day, slope heats, air becomes less dense, flows up from valley

Mountain Winds Mountain WaveMountain Wave –Air deflected after flowing over mountain oscillates (or bounces) up and down violently in a wave pattern.

Gusts and Squalls GustGust –Sudden and brief increase in wind speed and direction (several seconds) –Usually caused by mechanical turbulence SquallSquall –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 directionVeering is increase in wind direction Backing is decrease in wind directionBacking is decrease in wind direction Wind veers and increases with altitude (due to lack of surface friction)Wind veers and increases with altitude (due to lack of surface friction) Diurnal VariationDiurnal Variation –Wind backs and decreases at night –Wind veers and increases during day (more ground heating)

Wind Effects EddiesEddies –Swirling air or vortices –Produced by friction between moving air and ground

Wind Effects Dust DevilsDust Devils –Super-heated concentrated lows on hot, clear, stable, days –Made visible by dust or sand

Wind Effects TornadoesTornadoes –Very concentrated, violent lows formed in unstable weather

Wind Effects Jet StreamJet 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