ATM OCN (Meteorology) 100
WIND:
PART III - RESULTANT ATMOSPHERIC MOTIONS
Summer 2004
Lecture #15 Scheduled for:
12 JUL 2004 (M)
Recommended Readings from Moran (2002):
pages 178-183; 306-307; 240-244; 307-309.
Today's Lecture Objectives:
- To explain how the various forces are joined in hydrostatic equilibrium, geostrophic wind, gradient wind and surface winds.
- To describe the hydrostatic equilibrium concept and its implications.
- To describe the formation of a sea/land breeze regime and discuss the principle it illustrates.
- To list the assumptions and properties of the geostrophic wind approximation.
- To compare and contrast geostrophic winds with the observed surface winds.
- To describe the effect of friction upon the speed and direction of the horizontal surface winds.
- To sketch a diagram (with isobars and wind arrows) showing the direction of the winds associated with cyclones and anticyclones in both the Northern and Southern Hemispheres.
- To explain the relationship between horizontal and vertical motions.
- To demonstrate Dines' Compensation Principle and to present examples of how the vertical motion of the air is linked to the horizontal motion of air.
- To explain why cyclones are typically cloudy and stormy, while anticyclones are commonly fair weather systems.
Outline:
Series continues from THE THEORY OF WINDS: PART II - FUNDAMENTAL FORCES
A. INTRODUCTION
- Overview
- Buys-Ballot Rule
- Fundamental assumptions
B. HORIZONTAL EQUATION OF ATMOSPHERIC MOTION
- Reviewing the Word Equation
- The Hydrostatic Balance Concept
- As a Result
C. FLOW RESPONDING TO PRESSURE GRADIENT FORCE - LOCAL WINDS
- Assumptions
- Examples
- Sea-Land Breeze Circulation
- Mountain-Valley Breeze Circulation
- City-Country Circulation
D. STRAIGHT-LINE, BALANCED, FRICTIONLESS MOTION - "GEOSTROPHIC FLOW"
- Definition
- Assumptions
- Concept of Geostrophic Balance
- Resultant Diagrams
- Implications of the Geostrophic Balance
E. BALANCED FLOW IN THE FRICTION LAYER
- The Nature of Friction
- The Friction Layer
- The Effect of Friction upon the Geostrophic Wind
- Assumptions
- Resultant Diagrams
- Variations of Near-Surface Winds with Height
F. CURVED, HORIZONTAL BALANCED MOTION - "GRADIENT FLOW"
- Assumptions
- Forces (accelerations) Associated with Curved Flow
- Gradient flow without Friction
G. GRADIENT FLOW WITH FRICTION
- Applicability to the Atmosphere
- Situation
- Resultant Diagrams
H. RELATIONSHIPS BETWEEN HORIZONTAL & VERTICAL MOTIONS
- Dilemma
- Convergence / Divergence
- Principle of Mass Continuity
- Dines' Compensation
- Resultant Vertical Motions
- Implications of Dines' Compensation
I. VORTICES AND VORTICITY
- Definitions
- Characteristic Vortex Features
Links to Other References:
The Forces & Wind module from Weather World 2010 (Univ. of Illinois-Urbana-Champaign).
See the mpg viewer of the geostrophic wind as well as the sea and land breeze sections.
Latest revision: 26 July 2004 (0330 UTC)
Produced by Edward J. Hopkins, Ph.D.
Department of Atmospheric and Oceanic Sciences
University of Wisconsin-Madison Madison, WI 53706
hopkins@meteor.wisc.edu
URL: aos100/lectures/s0415wind3.html