Lesson 1
Chapters 1 & 2
Lesson 2
Chapter 3 & Instrument Supplement
Lesson 3
Weather Maps
Lesson 4
Chapter 4
Lesson 5
Chapter 5
Lesson 6
Chapter 6
Lesson 7
Chapter 7
Lesson 8
Chapter 8
Lesson 9
Chapter 9
Lesson 10
Chapter 10
Lesson 11
Wind Shear and Turbulence
Lesson 12
Icing
Lesson 13
Visibility
Lesson 14
Case Study/Self-Briefing
Lesson 15
Case Study/Self-Briefing
Lesson 16
Case Study/Self-Briefing

LESSON 4

Friction

Friction opposes, or decelerates, the wind. Friction is largest in the atmospheric boundary layer, the air layer nearest the ground. Friction always slows down the wind, and therefore also reduces the Coriolis force. The magnitude of frictional force is determined by the roughness of the surface and the speed of the wind. The force of friction over still water or an ice pond is small. Trees in a forest strongly oppose the wind, so the frictional force of forests is large. While the wind may be blusterous over an ice pond, it will be more calm in the woods.

Meteorologists consider the effects of friction when dealing with the air within 20 to 200 meters of the surface. This layer is called the surface layer; it is here that frictional drag is important in determining wind direction and speed. In the surface layer friction acts to slow the wind, and thus always acts opposite to the wind direction. Its magnitude increases with increasing wind speed.

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This web based lab section is being developed with assistance from the College of Letters and Science and the Cooperative Institute of Meteorological Satellite Studies.   Material presented is Copyrighted (C) 2000 by Steve Ackerman .  Feel free to use this material for non-profit educational purposes!