Lab5
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Lab5 10/09/2013
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Lab5. 10/09/2013. Pressure Levels. 3 forces that control wind direction? PGF or HGF, Coriolis , Friction What is geostrophic wind? PGF = Coriolis Wind blows parallel to isobars and height lines Is friction greatest at low or high elevations? Low, because of the earth’s surface! - PowerPoint PPT Presentation
Transcript of Lab5
Lab510/09/2013
Pressure Levels
3 forces that control wind direction? PGF or HGF, Coriolis, Friction
What is geostrophic wind? PGF = Coriolis Wind blows parallel to isobars and height lines
Is friction greatest at low or high elevations? Low, because of the earth’s surface!
Friction slows the wind and reduces the effect of the coriolis force
Friction
Air in motion near the earth’s surface is slowed by contact with the ground
The magnitude of friction is dependent on the “roughness” of the surface
Where is friction greater? Over land or over water?
Friction
Pressure and Boiling Water
ScienceBlogs
Pressure and Boiling Water:Higher Pressure (Lower Elevation)
Boiling Water at high pressure
Boiling Water
Water vapormolecules
Pressure and Boiling Water:Lower Pressure (Higher Elevation)
Boiling Water
Water vapormolecules
Pressure Levels
Pressure Levels and Friction
Surface Pressure What is the height
of the “surface” pressure?
Wind crosses isobars at a rather large angle
Pressure Levels and Friction
850mb-heights Wind crosses
height lines at a small angle
Pressure Levels and Friction
500mb-heights Wind blows parallel
to height lines
Buys-Ballot’s Law If you stand with the wind at your back on a constant
pressure surface, lower heights (lower pressure) will be on your left in the Northern Hemisphere
Jet Stream!
Vertical profile of winds measured at Caribou, ME
Mandatory Pressure Levels – pressure levels which radiosondes always take measurements
Jet Stream The jet stream is caused by differences in temperature
between the tropics and the polar regions The greater the temperature difference, the faster the jet
stream Remember: Pressure decreases faster in cold air than in
warm air!!!!!!!!
L HPGF
North Pole
Tropics
North Pole
Tropics11000m
9800m
9950m
11000m
9950m
Winter Summer
*JetStreaks
Do you think it is faster to fly from Seattle to Boston,or from Boston to Seattle?
Temperature and Altitude
Buoyancy and Vertical Ascent Less dense air rises More dense air sinks Think about a hot air balloon…why does it rise?
Lab 5 Problems:
6.13 6.18 a, b, c 7.1 a, b, c 7.2 b, c 7.8 a, b, c 7.10 a, b 8.6 a, b
