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Part 9 9.2 Weather and climate What are climatic elements? What are their distribution patterns? Part A © Oxford University Press 2010 Quit Part 9 Weather and climate How does insolation affect climate? We Wehave havealready also learned learned that the insolation the concept ofisair basic factor that temperature in causes Part 7. In different this Unit, ofon we patterns will focus climatic elements. other elements. Insolation Affects Air temperature Affects Air pressure Affects Affects Precipitation (link to Part B) Affects Wind © Oxford University Press 2010 Affects Quit Part 9 © Oxford University Press 2010 Weather and climate Quit Part 9 Weather and climate What are air pressure and winds? Does air have weight? Let's find it out! Please click above for footage © Oxford University Press 2010 Quit Part 9 Weather and climate What are air pressure and winds? Air ( has / does not have ) weight. When air presses on the ground, it creates pressure. It is known as ___________. air pressure Air Since the movement of air may form clouds and rain, air pressure is also an important element of Air weather and climate. The difference in air pressure on the ground generates air movement, known as _______. wind © Oxford University Press 2010 Quit Part 9 Weather and climate What are air pressure and winds? What factors would affect air pressure? Air pressure Altitude © Oxford University Press 2010 Air temperature Air movement Quit Part 9 Weather and climate What are air pressure and winds? What are the major air pressure belts? WeHow learned doesthat the insolation on the uneven distribution earth’s surface is of insolation affect ( evenly / unevenly ) air pressure? distributed. Uneven distribution of insolation Great variations in air temperature among latitudes Air movement Creating four air pressure belts © Oxford University Press 2010 Quit Part 9 Weather and climate What are the major air pressure belts? 1 Equatorial low How does the heated air move at the equatorial regions? A lot of insolation received at the __________ Equator Equatorial low Solar radiation Therefore, The heatedaair ( lowexpands / and ( sinks high) pressure / rises belt).is formed. © Oxford University Press 2010 Quit Part 9 Weather and climate What are the major air pressure belts? 2 Polar highs Polar high Solar radiation The angle of the sun is ( small / large ) at the poles Equatorial low Polar high © Oxford University Press 2010 How does the Therefore, a ( low- / cold) pressure air move at highbelt is the places near formed. the Poles? Solar radiation Quit Part 9 Weather and climate What are the major air pressure belts? 3 Subtropical highs Polar high Subtropical high Equatorial low Subtropical high Air risesair at diverges the Thethat sinking at Equator diverges the the earth’s surfaceatand upper atmosphere. replaces the rising air at the Equator. Air temperature falls with increasing latitude.air Part of the sinking moves poles. The air towards begins tothe cool and ( sink / rise ) at around 30ºN and 30ºS. The sinking air forms ( low- / high- ) pressure belts there. Polar high © Oxford University Press 2010 Quit Part 9 Weather and climate What are the major air pressure belts? 4 Subpolar lows Polar high Subpolar low Subtropical high Equatorial low Subtropical high Subpolar low Polar high © Oxford University Press 2010 The sinking air from polar highs move towards the Equator. The two air masses from happens polarWhat highs and subtropical when the coldand air the highs converge from the poles ( cold / warm ) air rises. meet the warm This forms ( low- / air from high- ) pressure belts. subtropical The rising air diverges highs? and replaces the sinking air at both the subtropical highs and the polar highs. Quit Part 9 Weather and climate What is the planetary wind system? _______ Wind is the movement of air caused by pressure differences. high Air moves from ______pressure areas to ______low pressure areas. If there are no other factors affecting the flow of air, how will the air flow between the Equator and the poles? © Oxford University Press 2010 Quit Part 9 Weather and climate What is the planetary wind system? Direction of rotation North Pole Deflect to the right Northern Hemisphere Deflect to the left Southern Hemisphere © Oxford University Press 2010 Air ( can the / cannot However, rotation) of move in a straight line on the earth affects the a rotating sphere. movement of air. Rotation-induced _____________ Coriolis force causes winds to deflect. In which directions do the winds in the two hemispheres deflect to respectively? Quit Part 9 Weather and climate What is the planetary wind system? How does air move under Coriolis force? © Oxford University Press 2010 Quit Part 9 Weather and climate What is the planetary wind system? What are the three major wind belts? N N Westerlies (south-westerlies) N Trade winds (north-easterlies) N This global wind system is known as the ________ planetary _____________. wind system © Oxford University Press 2010 Polar easterlies (north-easterlies) Trade winds (south-easterlies) N N Westerlies (north-westerlies) Polar easterlies (south-easterlies) Quit Part 9 Weather and climate What is the planetary wind system? Horse latitudes Slow sinking air forms calm or light winds Doldrums Little pressure variation Why narrower are windszones Two in two are ofthese light wind zonesbetween light? the found major wind belts. © Oxford University Press 2010 Quit Part 9 Weather and climate What is the planetary wind system? Polar front The boundary at around 60ºN and 60ºS, where cold air from the poles and warm air from subtropical highs meet, is called polar front. © Oxford University Press 2010 Trade winds converge and rise along a boundary in the doldrums, known as the intertropical convergence Winds from north zone (ITCZ). Polar front and south converge and rise at two major boundaries. Quit Part 9 Weather and climate What is the planetary wind system? Are air pressure belts and wind belts stationary? No, they are not stationary. They shift according to the location of the overhead sun. © Oxford University Press 2010 Quit Part 9 Weather and climate What is the planetary wind system? How do the air pressure belts and wind belts shift with the seasons? In July The overhead sun moves to N the Equator S The region shifts Thehottest south-east trade winds in the ( northwards / southwards ). Southern Hemisphere will be The pressure and wind trade deflected intobelts ___________ south-west belts shift ( northwards winds after crossing the/ Equator. southwards ). © Oxford University Press 2010 Quit Part 9 Weather and climate What is the planetary wind system? How do the air pressure belts and wind belts shift with the seasons? In January The overhead sun moves to N the Equator S The hottest region shifts The north-east trade winds ( northwards / southwards ). in the Northern Hemisphere will be The pressure belts and wind deflected into ___________ north-west trade belts shift ( northwards / winds after crossing the Equator. southwards ). © Oxford University Press 2010 Quit Part 9 Weather and climate Read the are It Why is because following maps pressure land and sea showing the belts absorb and lose distribution of unevenly heat at different pressure belts in distributed? rates. July and January. July January © Oxford University Press 2010 Quit Part 9 Weather and climate How do land and sea affect the global distribution of air pressure belts? July Subpolar low It is broken and forms low-pressure cells over the land Intense low-pressure cells Developed over the heated landmasses Subtropical high It is broken and forms highpressure cells over the sea Overhead sun Pressure belts shift northwards Equatorial low Shifts to the north of the Equator Subtropical high It shifts northwards and extends over the land It forms a continuous belt over the sea Subpolar low © Oxford University Press 2010 Quit Part 9 Weather and climate How do land and sea affect the global distribution of air pressure belts? It is broken and forms low-pressure cells Subpolar low over the sea January Subpolar low Intense high pressure cells Develops over land with very low temperature Subtropical high It extends over the landmass of Asia and North America Equatorial low It extends over northern Australia, central Africa and central South America Overhead sun Pressure belts shift southwards It is broken into cells over the sea Subtropical high It forms a continuous belt over the sea Subpolar low © Oxford University Press 2010 Quit Part 9 Weather and climate What is the world wind pattern? The world wind pattern is different from the planetary wind system. Is the world wind pattern the same as the Factors such as rotation of the earth, seasonal changes planetary system? of the overhead sun and wind effects of land and sea may affect the world wind pattern. January July © Oxford University Press 2010 Quit Part 9 Weather and climate What factors would affect air pressure? 1 Altitude Why do climbers feel difficult to breathe at the Himalayas? Mountain © Oxford University Press 2010 Quit Part 9 Weather and climate What factors would affect air pressure? 1 Altitude The atmosphere is ( thinner / thicker ) and ( less dense / denser ) The atmosphere is ( thinner / thicker ) and ( less dense / denser ) ( Low / High ) Higher altitude pressure Mountain ( Low / High ) pressure Lower altitude In the lower atmosphere, air pressure ( decreases / increases ) with increasing altitude. © Oxford University Press 2010 Quit Part 9 Weather and climate What factors would affect air pressure? 2 Air temperature The higher the air temperature, the lower the air pressure near the earth’s surface. High temperature Low temperature When air is heated, it ________ expands and _______. rises When air cools down, it _________ contracts and _______. sinks Low pressure High pressure Earth’s surface © Oxford University Press 2010 Earth’s surface Quit Part 9 Weather and climate What factors would affect air pressure? 3 Air movement Under condition will athe How willwhich the air density near higher air pressure resulted? earth’s surfacebe change? Air converges __________ and rises In this case, the air density near the earth’s surface ( lowers / gets higher ). © Oxford University Press 2010 Air sinks and diverges ________ near the earth’s surface In this case, the air density near the earth’s surface ( lowers / gets higher ). Quit
