1. Aim: How does atmospheric pressure generate winds?

2. How are the winds moving in this hurricane?

3. How can we describe this map?
Isobars – lines which connect points of equal pressure
Pressure gradient – rate of change in pressure between two locations
Steep pressure gradient: Isobars close together – strong (high) wind speeds
Gentle pressure gradient: Isobars far apart – gentle (low) wind speeds

4. How does wind move?
Winds a move from high pressure areas to low pressure areas, resulting from uneven heating of Earth's atmosphere
How do we measure wind speed and direction?
Anemometer – instrument used to measure wind speed
Wind vane – instrument used to measure wind direction

5. Cyclones (Low Pressure) Anticyclones (High Pressure) Warm & moist air
Precipitation
Cool, dry air
Bad Weather
Good Weather
Condensation occurs
Air contracts – more dense (sinks) A
Air cools & expands B
Warm, wet air rises – less dense
Air warms up due to compression L
Winds flow High to Low H
Cyclones (Low Pressure)
Anticyclones (High Pressure)
Warm & moist air
Cool & dry air
Lowest pressure in the center
Highest pressure in the center
Winds move to center (converge)
Winds move out of center (diverge)
Winds rotate counter clockwise
960
940
920 L
960
940
920 L
Winds rotate clockwise
1003
1004
1005 H
1003
1004
1005 H
Pressure increases outwards
Pressure decreases outwards
960
1003
940
1004
920
1005
Lo Co
LICC L H
Hi Di
HOC

6. Water: cooler, heats up slower, high specific heat
High Pressure
Low Pressure
Low Pressure
High Pressure
Cold Temp
Warm Temp
Warm Temp
Cold Temp
Sea Breeze – wind flow from high to low
Land Breeze
Land: warmer, heats up faster, low specific heat
Water: cooler, heats up slower, high specific heat
Water: warmer, cools down slower, high specific heat
Land: cooler, cools down faster, low specific heat
Sea Breeze – winds flow from water to land
Land Breeze – winds flow from land to water

7. Mountain Windward Side “Low Pressure” Leeward Side “High Pressure”
Adiabatic Cooling
Adiabatic Warming
Windward Side
“Low Pressure”
Leeward Side
“High Pressure”
Air cools to dewpoint temp, condensation occurs
Cool, dry air
Sinks – more dense
Cools & expands
Air warms due to compression (molecules come closer together)
Warm, wet air rises – less dense
Mountain
Prevailing Winds
Rainforest
Cool & Wet
Desert
Warm & Dry

8. Answer the questions on the worksheet
Summary Activity
Answer the questions on the worksheet
The diagram below shows the isolines of air pressure around a low-pressure center. On which side of the low-pressure center will the wind speed be greatest?
East

9. Extra Questions

10. 1003
1004
1005 H
960
940
920 L

11. Winds move to center (converge) Winds rotate counter clockwise
Low Pressure
High Pressure A B L H
(Low Pressure)
(High Pressure)
Warm & moist air
Cool & dry air
Lowest pressure in the
pressure in the center
Winds move to center (converge)
Winds move out of center (diverge)
Winds rotate counter clockwise
Winds rotate clockwise
Pressure increases outwards
Pressure decreases outwards L
960
940
920 L H