Telematic Teaching Project GEOGRAPHY The Atmosphere Global air

Telematic Teaching Project GEOGRAPHY The Atmosphere: Global air circulation

CLIMATE AND WEATHER • • • High and low pressures Circulation patterns Geostrophic flow Föhn winds Monsoon winds

HIGH AND LOW PRESSURES

High- and low pressures

HIGH AND LOW PRESSURES HIGH PRESSURE • Air sinking • Anti-clockwise • Air moves away from HP LOW PRESSURE • Air rising • Clockwise • Air moves towards LP

TEMPERATURE, AIR PRESSURE AND WIND COLD AIR SINKS RISING WARM AIR COLD AIR SINKS LP HP HP Via Afrika

What do you remember? LP a) b) c) d) e) HP Would a HP or LP will be found at the man? Give a reason for your answer Would a HP or LP will be found at the woman? Give a reason for your answer. What is the movement of air from the woman towards the man called?

CIRCULATION PATTERNS

GLOBAL AIR CIRCULATION PATTERN POLAR HP SUB POLAR LP • Very warm • Ascending air • Low Pressure • Very Cold • Decending air • High Pressure Westerlies SUBTROPICAL HP Tropical easterlies Winds deflect to RIGHT in NH EQUATORIAL LP (ITCZ) Winds deflect to LEFT in SH • Air spun away • Low Pressure Tropical easterlies SUBTROPICAL HP Westerlies SUB POLAR LP POLAR HP • Air from equator sinks here • High Pressure

Coriolus force

GLOBAL AIR CIRCULATION PATTERN POLAR HP SUB POLAR LP • Very warm • Ascending air • Low Pressure • Very Cold • Decending air • High Pressure Westerlies SUBTROPICAL HP Tropical easterlies Winds deflect to RIGHT in NH EQUATORIAL LP (ITCZ) Winds deflect to LEFT in SH • Air spun away • Low Pressure Tropical easterlies SUBTROPICAL HP Westerlies SUB POLAR LP POLAR HP • Air from equator sinks here • High Pressure

Cold air sinks Polar cell Air spun away 90° N Pola r win ds 60° N Ferrel cell Westerly winds 30° N Air flows back to Equator 0° TRI-CELULAR MODEL Cooler air sinks Hadley cell Hot air rises

What do you remember? a) Name the cells at 1, 2 and 3 b) The (Subtropical HP/ Sub polar HP is found at 4 c) (Southwesterly / Northwesteriy wind is found at 5 3 2 5 4 1

GEOSTROPHIC FLOW

Forces Coriolis force causes the deflection of air to the RIGHT in the NH an to the LEFT in the SH Pressure gradient is the force that causes air to move from a HIGH to a LOW pressure What happens when these two forces combine?

Geostrophic flow in the Southern Hemisphere Why can no deflection to the left take place at X? Caused by the combined effects of pressure gradient and Coriolis force X

FÖHN WINDS

Föhn wind What is a Föhn wind? Leeward side Windward side • Hot , dry wind that originate in mountainous areas • Air descends on leeward side and heats up

DALR: 1°C/100 m WALR: 0, 5°C/100 R 12, 5°C R AL `700 m W L A W `600 m `400 m 14°C 14, 5°C `300 m 16°C 17°C LR R L A D 15°C DA `200 m 15°C 14°C LR R L 13, 5°C W A DA `500 m `100 m Cloud base 13°C 18°C

MONSOON WINDS

Monsoon winds SUMMER Land warm WINTER LP HP Land cold HP Dry NE Monsoon Moist SW Monsoon Sea cold LP Sea warm

Glenn. Samaai@westerncape. gov. za