Lab5 10/09/2013. Pressure Levels 3 forces that control wind direction? PGF or HGF, Coriolis,...

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

Tropics

11000m

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