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Global air circulation

Tsiamo Mokgopa
Tsiamo Mokgopa

This document discusses global air circulation patterns driven by uneven heating of the atmosphere. It describes three main factors that influence winds: pressure gradient force, Coriolis force, and friction force. Unequal heating creates high and low pressure systems that drive winds according to these forces. The document outlines the major wind systems in different latitudes, including the trade winds near the equator; westerlies in mid-latitudes between subtropical highs and subpolar lows; and polar easterlies near the poles. Diagrams are provided showing typical January and July surface pressure patterns and winds in each region.

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GLOBALAIR CIRCULATION Presented by : Mr T Mokgopa : t.mokgopa9@gmail.com
GLOBAL WIND AND PRESSURE BELTS AS A RESPONSE TO THE UNEQUAL HEATING OF THE ATMOSPHERE Equatorial Regions receive more insolation than Polar Regions. Land/ Earth heats up and cools in a cycle of a day. The mechanism that sets up the Earths general circulation pattern is the Latitudinal heat transfer.
AIR PRESSURE AND THE RELATIONSHIP BETWEEN AIR PRESSURE AND TEMPERATURE Air pressure is created by molecules that constitute air through their motion, side, and number. Pressure and density both decrease with an increase in altitude. Relationship between Air Pressure and Temperature: Low Pressure System: Warmer Temperatures High Pressure System: Colder Temperatures
WIND, WIND SPEED, WIND DIRECTION AND NAMING OF WINDS Simply put, Wind refers to the horizontal motion of air. A vertical component of wind results from turbulences. Properties of wind: Speed and Direction. Anemometer: Measures wind speed. Wind Vane: Determines wind direction. WINDS ARE NAMED FROM THE DIRECTION FROM WHICH THEY ORIGINATE.
DRIVING FORCES WITHIN THE ATMOSPHERE 1. Gravitational Force. 2. Pressure Gradient Force. 3. Coriolis Force. 4. Friction Force
PRESSURE GRADIENT FORCE This force drives air from higher barometric pressure to lower barometric pressure. A Gradient is the rate of change in some property over distance. Unequal heating of Earth results in the existence of High-pressure and Low-pressure systems. When the two varying air masses are near each other, a pressure gradient force develops. Vertical air movement can also cause pressure gradient force. High-pressure: Subsiding and diverging air. Low-pressure: Rising and converging air.
CORIOLIS FORCE This a force that deflects wind on Earths rotating surface. If Earth was not rotating, wind would travel in a straight pattern as they move from areas of high- pressure, to areas of low-pressure. The Coriolis Force deflects anything flying across the Earths surface. The strength of the Coriolis Force varies at different latitudes. There is no Coriolis Force at the Equator.
FRICTION FORCE The Frictional force drags wind as it moves across the surface of the Earth. Without the frictional force, the wind would continually flow at higher speeds. Generally, as wind flows through rougher surfaces, the presence of friction is higher.
PRIMARY PRESSURE AREAS AND ASSOCIATED WINDS JANUARY AVERAGE SURFACE BAROMERTIC PRESSURES JULY AVERAGE SURFACE BAROMETRIC PRESURES
EQUATORIAL LOW/ ITCZ: Warm and Rainy Located at the 0属 latitude. Receives constant high altitude of the Sun. Associated with the Low-pressure system. Intertropical convergence zone (ITCZ): Identified by bands of clouds along the equator. Associated with TRADE WINDS Winds are calm within the ITCZ. REASON? Weak Pressure Gradient. These equatorial calm conditions are referred to as Doldrums.
SUBTROPICAL HIGHS: Hot and Dry Located between 20属 and 35属 latitudes in both hemispheres. These subtropical anticyclones generally form as air above subtropics in pushed downward. Since warm air can absorb water vapour, the descending warm air is relatively dry. Several high-pressure areas are dominant in the Subtropics. Bermuda High: The Atlantic subtropical high in the NH. In the SH, three large high-pressure centres dominate the Pacific, Atlantic, and Indian Oceans. Associated with the Westerlies.
SUBPOLAR LOWS: Cool and Moist Two low-pressure cyclonic cells exist over the oceans around 60属 N. Aleutian Low & Icelandic Low. These cells are dominant in winter. Polar front: areas of contrast where masses of air with different characteristics meet.
POLAR HIGHS: Frigid and Dry Characterized by weak cells. The polar regions receive little energy from the Sun. Associated with the Polar Easterlies. Characterized by cold and dry winds that move away from Polar Regions in an anticyclonic direction. The Antarctic has stronger and persistent high-pressure system, the Antarctic High.
THE TRI-CELLULAR CIRCULATION WITH WINDS
THE END!!!

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Global air circulation

  • 1. GLOBALAIR CIRCULATION Presented by : Mr T Mokgopa : t.mokgopa9@gmail.com
  • 2. GLOBAL WIND AND PRESSURE BELTS AS A RESPONSE TO THE UNEQUAL HEATING OF THE ATMOSPHERE Equatorial Regions receive more insolation than Polar Regions. Land/ Earth heats up and cools in a cycle of a day. The mechanism that sets up the Earths general circulation pattern is the Latitudinal heat transfer.
  • 3. AIR PRESSURE AND THE RELATIONSHIP BETWEEN AIR PRESSURE AND TEMPERATURE Air pressure is created by molecules that constitute air through their motion, side, and number. Pressure and density both decrease with an increase in altitude. Relationship between Air Pressure and Temperature: Low Pressure System: Warmer Temperatures High Pressure System: Colder Temperatures
  • 4. WIND, WIND SPEED, WIND DIRECTION AND NAMING OF WINDS Simply put, Wind refers to the horizontal motion of air. A vertical component of wind results from turbulences. Properties of wind: Speed and Direction. Anemometer: Measures wind speed. Wind Vane: Determines wind direction. WINDS ARE NAMED FROM THE DIRECTION FROM WHICH THEY ORIGINATE.
  • 5. DRIVING FORCES WITHIN THE ATMOSPHERE 1. Gravitational Force. 2. Pressure Gradient Force. 3. Coriolis Force. 4. Friction Force
  • 6. PRESSURE GRADIENT FORCE This force drives air from higher barometric pressure to lower barometric pressure. A Gradient is the rate of change in some property over distance. Unequal heating of Earth results in the existence of High-pressure and Low-pressure systems. When the two varying air masses are near each other, a pressure gradient force develops. Vertical air movement can also cause pressure gradient force. High-pressure: Subsiding and diverging air. Low-pressure: Rising and converging air.
  • 7. CORIOLIS FORCE This a force that deflects wind on Earths rotating surface. If Earth was not rotating, wind would travel in a straight pattern as they move from areas of high- pressure, to areas of low-pressure. The Coriolis Force deflects anything flying across the Earths surface. The strength of the Coriolis Force varies at different latitudes. There is no Coriolis Force at the Equator.
  • 8. FRICTION FORCE The Frictional force drags wind as it moves across the surface of the Earth. Without the frictional force, the wind would continually flow at higher speeds. Generally, as wind flows through rougher surfaces, the presence of friction is higher.
  • 9. PRIMARY PRESSURE AREAS AND ASSOCIATED WINDS JANUARY AVERAGE SURFACE BAROMERTIC PRESSURES JULY AVERAGE SURFACE BAROMETRIC PRESURES
  • 10. EQUATORIAL LOW/ ITCZ: Warm and Rainy Located at the 0属 latitude. Receives constant high altitude of the Sun. Associated with the Low-pressure system. Intertropical convergence zone (ITCZ): Identified by bands of clouds along the equator. Associated with TRADE WINDS Winds are calm within the ITCZ. REASON? Weak Pressure Gradient. These equatorial calm conditions are referred to as Doldrums.
  • 11. SUBTROPICAL HIGHS: Hot and Dry Located between 20属 and 35属 latitudes in both hemispheres. These subtropical anticyclones generally form as air above subtropics in pushed downward. Since warm air can absorb water vapour, the descending warm air is relatively dry. Several high-pressure areas are dominant in the Subtropics. Bermuda High: The Atlantic subtropical high in the NH. In the SH, three large high-pressure centres dominate the Pacific, Atlantic, and Indian Oceans. Associated with the Westerlies.
  • 12. SUBPOLAR LOWS: Cool and Moist Two low-pressure cyclonic cells exist over the oceans around 60属 N. Aleutian Low & Icelandic Low. These cells are dominant in winter. Polar front: areas of contrast where masses of air with different characteristics meet.
  • 13. POLAR HIGHS: Frigid and Dry Characterized by weak cells. The polar regions receive little energy from the Sun. Associated with the Polar Easterlies. Characterized by cold and dry winds that move away from Polar Regions in an anticyclonic direction. The Antarctic has stronger and persistent high-pressure system, the Antarctic High.