Global Air Circulation
Pressure Belts
● Along Equator, warm air expands & rises in convection currents
● Causes low pressure cells = Equatorial Low Pressure Belt
● ITCZ = Intertropical Convergence Zone
● As air rises, it cools
● Air of same temperature as surrounding air, stops rising
● Air diverges pole wards
● Air begins to sink
● Air gets compressed & temperature rises
● cold air subsides causing polar high pressure = Subtropical High Pressure
● Cold air converges with warm air = Sub Polar Low Pressure
●
● Southern Hemisphere = Winter : ITCZ migrates North
Summer : ITCz migrates South
, Pressure Gradient Force & Wind
● Causes air to move high pressure towards low pressure
● PGF stronger when steeper & stronger wind result
● Weather winds blow when PGF gentle
Coriolis Force
● Once wind blows along pressure gradient, Earth’s rotation = winds deflect
● Rotation speed 0 km/h at Poles, about 1 670 km/hat Equator
● Force of deflection = Coriolis Force
● Does not occur at equator (within 5° )
● Dependent strength of winds
Force is stronger when wind stronger
● Deflects winds from North to South direction
Ferrel’s Law
● Law demonstrating Coriolis Force
● Moving matter deflected from its course by force of Earth’s rotation
● Ferrel's law = moving matter deflected to left (Southern Hemisphere)
Deflected to right (Northern Hemisphere)
Geostrophic Flow
● Air moves high pressure to low pressure = Pressure Gradient Force (PGF)
● Air moves how Coriolis Force deflects it due to rotation of the Earth
● As air moves from HP speed increases & so does deflectio
● Deflection increases till Coriolis & Pressure Gradient same
● Then air moves along Isobars (lines on a weather map joining together places of equal
atmospheric pressure)
Pressure Belts
● Along Equator, warm air expands & rises in convection currents
● Causes low pressure cells = Equatorial Low Pressure Belt
● ITCZ = Intertropical Convergence Zone
● As air rises, it cools
● Air of same temperature as surrounding air, stops rising
● Air diverges pole wards
● Air begins to sink
● Air gets compressed & temperature rises
● cold air subsides causing polar high pressure = Subtropical High Pressure
● Cold air converges with warm air = Sub Polar Low Pressure
●
● Southern Hemisphere = Winter : ITCZ migrates North
Summer : ITCz migrates South
, Pressure Gradient Force & Wind
● Causes air to move high pressure towards low pressure
● PGF stronger when steeper & stronger wind result
● Weather winds blow when PGF gentle
Coriolis Force
● Once wind blows along pressure gradient, Earth’s rotation = winds deflect
● Rotation speed 0 km/h at Poles, about 1 670 km/hat Equator
● Force of deflection = Coriolis Force
● Does not occur at equator (within 5° )
● Dependent strength of winds
Force is stronger when wind stronger
● Deflects winds from North to South direction
Ferrel’s Law
● Law demonstrating Coriolis Force
● Moving matter deflected from its course by force of Earth’s rotation
● Ferrel's law = moving matter deflected to left (Southern Hemisphere)
Deflected to right (Northern Hemisphere)
Geostrophic Flow
● Air moves high pressure to low pressure = Pressure Gradient Force (PGF)
● Air moves how Coriolis Force deflects it due to rotation of the Earth
● As air moves from HP speed increases & so does deflectio
● Deflection increases till Coriolis & Pressure Gradient same
● Then air moves along Isobars (lines on a weather map joining together places of equal
atmospheric pressure)
