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CHAPTER 4

ATMOSPHERIC CIRCULATION

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INTRODUCTION• Mechanisms of global energy transfer• Factors affecting the strength of the

general circulation• The importance of angular momentum• The global circulation cells

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GLOBAL SURFACE WIND ZONES AND PRESSURE CELLS

• The role of Pressure Gradient Force (PG)• 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

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UPPER TROPOSPHERIC – LOWER STRATOSPHERIC CIRCULATION

• The geostrophic wind• The circumpolar vortex • Rossby Waves• Jet streams

– Their creation– Influence on circulation– Geographical location

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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

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BUSHFIRE WEATHER

• (Blocking) high pressure affected by approaching cold front

• Strong winds from the continental interior• High temperatures• Very dry conditions• Fuel availability

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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

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WINDS ASSOCIATED WITH HIGHS AND LOWS

• Pressure Gradient Force (PG)• Coriolis force (H)• Centrifugal force (C)• Friction (F)• Defining winds around highs and lows

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REGIONAL AND LOCAL CIRCULATION

• Defining the appropriate scale• Measuring the weather• Australian regional-scale circulation

systems– Foehn winds– The southerly buster– West coast trough

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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)