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!  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 vapor molecules

Pressure and Boiling Water: Lower Pressure (Higher Elevation) Boiling Water Water vapor molecules

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!!!!!!!!

North Pole Tropics North Pole Tropics 11000m 9800m 9950m 11000m 9950m Winter Summer

*Jet Streaks 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