1. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 CHAPTER 4 ATMOSPHERIC CIRCULATION

2. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 INTRODUCTION Mechanisms of global energy transfer Factors affecting the strength of the general circulation The importance of angular momentum The global circulation cells

3. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 GLOBAL SURFACE WIND ZONES AND PRESSURE CELLS The role of Pressure Gradient Force (P G ) Coriolis force and its influence on wind Intertropical Convergence Zone (ITCZ) The south-east trade winds The subtropical high pressure belts The westerlies Polar circulation

4. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 UPPER TROPOSPHERIC – LOWER STRATOSPHERIC CIRCULATION The geostrophic wind The circumpolar vortex Rossby Waves Jet streams –Their creation –Influence on circulation –Geographical location

5. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 SYNOPTIC CIRCULATION BRINGS WEATHER VARIATIONS Definition and scale Characteristics of synoptic high pressure systems Characteristics of synoptic low pressure systems How to read a weather map How high pressure aids egret migrations

6. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 BUSHFIRE WEATHER (Blocking) high pressure affected by approaching cold front Strong winds from the continental interior High temperatures Very dry conditions Fuel availability

7. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 SYNOPTIC CIRCULATION PATTERNS OVER AUSTRALIA Winter –SE trades affect the northern half (dry) –Westerlies influence the southern half Alternating high and low pressure systems Summer –NW monsoon affects the northern third –High pressure circulation affects the southern two- thirds –Influence of ocean along the coasts

8. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 WINDS ASSOCIATED WITH HIGHS AND LOWS Pressure Gradient Force (P G ) Coriolis force (H) Centrifugal force (C) Friction (F) Defining winds around highs and lows

9. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 REGIONAL AND LOCAL CIRCULATION Defining the appropriate scale Measuring the weather Australian regional-scale circulation systems –Foehn winds –The southerly buster –West coast trough

10. Chapter 4 © Oxford University Press, 2008. All rights reserved. 1 LOCAL WIND ENVIRONMENTS Drainage and katabatic flows Anabatic winds Sea breezes Land breezes Sea breeze ‘doctors’ in Western Australia The Morning Glory (Gulf of Carpenteria)