# WIND:  PART II - THEORY & FUNDAMENTAL FORCES

## Summer 2004

### Today's Lecture Objectives:

• To briefly describe Newton's three laws of motion.
• To describe the relationship between the observed winds and the horizontal atmospheric pressure field pattern, relating the spacing of isobars to the speed of wind.
• To identify the various forces that could act upon an air parcel to initiate, maintain and modify atmospheric motion.
• To explain why gravity only influences vertical motion and not horizontal motion of air.
• To describe the factors that influence the magnitude and direction of the pressure gradient force and its components - the horizontal and vertical pressure gradient force.
• To describe the influence of the Coriolis effect upon free-moving objects or fluids and list two factors that influence the magnitude of this effect.
• To describe the effect of friction upon the speed and direction of the horizontal surface winds and identify two factors influencing the magnitude of the friction force.
• To distinguish between centripetal force and centrifugal force and describe the factors that influence the magnitude and direction of the centripetal force.

### Outline:

#### B. CONCEPTS OF THE WIND - EXPLANATIONS OF ATMOSPHERIC MOTION

• Practical Problems
• Historical Concepts
• The Forces of Motion & Newton's Laws
• Implications of the Newtonian Laws
• Vectors, Forces and Units

#### B. FORCES ASSOCIATED WITH ATMOSPHERIC MOTION

• Reasons for Atmospheric Motions
• Complications involved with Atmospheric Motion
• Three Dimensional Equation of Motion for the Atmosphere
• The Forces
• Gravitational Force or Gravity
• Coriolis Effect or "Force"
• Frictional Force or Friction
• Centripetal Force
• Summarizing
##### Series continues as THE THEORY OF WINDS PART III - RESULTANT ATMOSPHERIC MOTIONS

The Forces & Wind module from Weather World 2010 (Univ. of Illinois-Urbana-Champaign). Check the mpg file that shows apparent motion on a rotating turntable (to simulate the Coriolis effect).

Latest revision: 26 July 2004 (0320 UTC)

Produced by Edward J. Hopkins, Ph.D.
Department of Atmospheric and Oceanic Sciences