Wind Wind is the general horizontal motion of air from one location to another based on differences in air pressure Wind is the general horizontal motion of air from one location to another based on differences in air pressure Air speed is measured by an anemometer Air speed is measured by an anemometer Air movement is governed primarily by Air movement is governed primarily by Pressure gradient force Pressure gradient force Coriolis force Coriolis force Friction force Friction force

What causes wind movement Direction is governed by the path of least distance between high pressure and low pressure Direction is governed by the path of least distance between high pressure and low pressure Pressure gradient Pressure gradient Speed will increase if there is a larger difference between pressures Speed will increase if there is a larger difference between pressures Steep pressure gradient Steep pressure gradient

RESULTANT WIND FUNCTION OF 3 THINGS FUNCTION OF 3 THINGS PGF + CF + FRICTION PGF + CF + FRICTION PGF AND CF ARE AT ODDS PGF AND CF ARE AT ODDS FRICTION DEFLECTS WINDS SLIGHTLY IN FAVOR OF PGF FRICTION DEFLECTS WINDS SLIGHTLY IN FAVOR OF PGF WHAT HAPPENS IN THE UPPER ATMOSPHERE? WHAT HAPPENS IN THE UPPER ATMOSPHERE?

BIRD’S EYE VIEW NORTHERN HEMISPHERE L H

Pressure gradient H L

The Coriolis Effect When wind moves from zones of high pressure to zones of low pressure it veers due to earth rotation When wind moves from zones of high pressure to zones of low pressure it veers due to earth rotation To the right in the northern hemisphere To the right in the northern hemisphere To the left in the southern hemisphere To the left in the southern hemisphere Equator faster rotation than the poles Equator faster rotation than the poles Demo – Demo – rc/content/visualizations/es1904/es1904page01.cfm ?chapter_no=visualization rc/content/visualizations/es1904/es1904page01.cfm ?chapter_no=visualization rc/content/visualizations/es1904/es1904page01.cfm ?chapter_no=visualization rc/content/visualizations/es1904/es1904page01.cfm ?chapter_no=visualization

Remembering the direction of bend in the coriolis effect Bends to the right Bends to the left

Effect of coriolis force Strongest at higher latitudes Strongest at higher latitudes Weakest at the equator Weakest at the equator The effect of coriolis increases with increasing windspeed The effect of coriolis increases with increasing windspeed The combined effect of coriolis and pressure gradient force makes winds travel parallel to isobars = The combined effect of coriolis and pressure gradient force makes winds travel parallel to isobars = Geostrophic Wind Geostrophic Wind

Friction force Effects of surface friction occur to ~ 5000 ft above the ground Effects of surface friction occur to ~ 5000 ft above the ground Cause winds to slow down and generally move across isobars Cause winds to slow down and generally move across isobars More pronounced when wind speeds are higher More pronounced when wind speeds are higher