Wind PDF

More winds! Wind Caused by unequal heating of Earth’s Atmosphere – Air moving advectionally – inland gets hot and cold sideways – along the faster than land close to Earth’s surface wat...

More winds! Wind Caused by unequal heating of Earth’s Atmosphere – Air moving advectionally – inland gets hot and cold sideways – along the faster than land close to Earth’s surface water because of the specific heat capacity of water and rock. Heated air rises - Surrounding air is sucked in, like a vacuum, under Winds can be measured by rising air to fill the empty space a wind vane & an anemometer Measure both Direction & windspeed  Upper level winds Upper-level winds measured by Doppler radar can Wind always named Radiosondes also measure upper- after direction Radiosondes are weather level winds from which it came balloons Metric Units - English Units – meters per second → knots → 1.15 miles (m/s) per hour Winds & Pressure Gradients On maps, isobars connect points of equal pressure Pressure gradient crosses isobars at right angle More tightly packed isobars →higher pressure gradient force Higher pressure gradient force → higher winds Local Winds Sea breeze / Land breeze: Early-morning calm – little heating yet – not a lot of movement Afternoon sea breeze – land warms faster in sun → low pressure inland, air flows towards mountains away from sea Night land breeze – land cools faster after sunset so air flows to the still relatively warm sea  In day, heating of mtn side drives rising air → valley breeze At night, air on mtn side cools, sinks into valley → mountain breeze Other Local Winds Fall winds – cold, dense air spills from highland onto lowlands Foehn winds – strong wind passes over mts Descends lee side, warming adiabatically Chinook is type of Foehn wind Santa Ana winds – southern California, winds from high pressure over desert cross mts and down into LA basin, warming adiabatically Coriolis Effect & Winds Aloft Broad-scale winds are affected by Coriolis Effect + Apparent force caused by Earth’s rotation + Earth rotates beneath moving air or water + Pulls moving air and water to right in northern hemisphere + Pulls to left in southern hemisphere + Strongest near poles, none along equator Geostrophic Wind At high altitude, no friction for air, it can just cruise and cruise Only pressure gradient force (pgf) & Coriolis force(Cf) Air begins at 950 mb Pulled toward 925 mb by (pgf) As it moves, Coriolis force (Cf) pulls it right Finally, pgf = Cf Wind parallel to isobars