2Key conceptsHow the earth’s spherical shape affects temperature and wind patternsWhy the tilt of the Earth’s axis causes seasonsHow Earth’s rotational motion affects wind and water currentsHow the continents influence ocean currentsHow the continents and the oceans affect the air above them.
3Solar energy and a spherical earth The Earth is a spherical, rotating, orbiting planet.These motions determine the amount of solar radiation absorbed by different parts of the planet.Latitude measures distances north or south of the equator in degrees of the angle made with the centre of the earth and the equator as the initial arm. The terminal arm is at the desired location. See text p. 454Longitude measures distances east or west from a reference line called the prime meridian which runs from the North Pole through Greenwich, England to the South Pole. It is also measured in degrees with the centre of the earth as the vertex and the line from the centre to the prime meridian as the initial arm. The terminal arm is at the desired location.
4Hot and ColdA beam of sunlight that strikes the earth at the equator is perpendicular to the surface of the planet. An identical beam striking at 45º N latitude or 45º S latitude would be more spread out than at the equator so the solar energy would be distributed over a larger area. Closer to the poles, the energy would be spread out over an even greater area
5Solar energy distribution on impact members. aol. com/pakulda/emstyg2 Solar energy distribution on impact members.aol.com/pakulda/emstyg2.htm
6The Four Seasons According to Vivaldi…. Consider Earth’s orbit around the sun and earth’s orientation in this orbit. See text p. 455
7Four Seasons Refer to text p. 456 Starting at the left, the tilt is toward Sun causing summer in the Northern hemisphere.As the earth moves counter clockwise, summer in the Northern hemisphere changes to fallAt the right end of its orbit, the tilt is away from the Sun and it is winter in the Northern hemisphere.At the two midpoints of the orbit, the Sun’s rays are perpendicular to the equator and equal amounts of energy are received by the hemispheres. These are the spring and autumn equinox.The orbit takes roughly days
8Circles and ZonesThe Arctic and the Antarctic Circles define the polar zones.The Tropic of Cancer and the Tropic of Capricorn define the tropical zone.Between each circle and each tropic is the temperate zoneZones are characterized by their general climate i.e the average weather conditions over many yearsPolar zones receive 24 h of sunlight at times but this does not impact global warming. Why?Temperate zones usually have a big difference between summer and winter since the sun’s rays are never perpendicular there.
9Worldwide Wind Currents Why do Weather Systems Generally Move from West to East in Canada?1. Uneven heating causes wind2. Cool air flows toward and under warm air3. Spherical shape of Earth causes uneven heating i.e more at the equator than at the poles.
10Worldwide Wind Currents 4. We’d expect air movements as shown on p.462, but the Earth is not a small sphere, it is very large. Global movements of air do not follow the simple pattern that land and sea breezes do and this does not account for the rotational effects of the Earth on wind patterns.5. Warm air from the equator rises north or south and then cools by the time it has reached about 30 N or S latitude.6. Some of that air then moves back toward the equator and some continues to move toward the poles but closer to the Earth.
11Worldwide Wind Currents 7. Cold polar air flows from the poles toward the equator but by the time it reaches 60 N or S latitude it has warmed sufficiently to begin rising again.8. This gives rise to three closed patterns of air movement seen on p.463 fig 14.8B9. Now we must account for the Earth’s rotation. The earth moves at about 300 m/s or 1200 km/h . We rotate along with the atmosphere but different places on the Earth move at very different speeds. See p. 463 at the bottom.
12Worldwide Wind Currents 10. Air between 30N and 60N latitude i.e. most of Canada and the U.S. is rising due to convection currents toward the North Pole, and rotating west to east along with the Earth. This combined effect causes the air to move from west to east and are called the prevailing westerlies. The effect of the Earth’s rotation on air or any object moving of the surface of the Earth is called the Coriolis Effect.
13Jet StreamWas discovered by pilots in 1944 flying at altitude of 10 km. Discovered the plane was travelling at 700 km/h faster than its top speed of 600 km/h.Jet streams are ribbons of extremely fast moving air near the top of the troposphere and are caused by contact between cold and warm air. They are found at the boundaries of polar and temperate zones and temperate and tropical zones.The polar jet stream affects our weather
14Jet StreamWhen prevailing westerlies are far enough north, they meet the cooler polar easterlies. The cooler air pushes beneath the warmer air and forces them up. As the air rises it encounters fewer barriers such as mountains so it accelerates. When this convection current combines with the Coriolis effect, the air travels at speeds from 100 km/h to 300 km/h. Jet streams can be thousands of km long and two or three hundred km thick. They are not circular and curve and meander north and south. Generally, the weather north of the stream is colder and south of the stream , warmer. In winter, wind patterns shift south along with the jet stream, and in the summer, the jet stream retreats far north. Both of these are due to the uneven heating pattern due to the Sun’s rays in summer and winter. See text p. 467
15Rivers in the SeaSurface ocean currents are primarily due to the influence of surface winds. Some of these carry warm water from the equator to the Arctic sea.Others carry cooler polar waters toward the equator.Although surface currents are started by wind, they are blocked and diverted by the continents.The Coriolis effect influences ocean currents as well as winds. Notice that ocean currents turn to the right in the Northern hemisphere and to the left in the Southern hemisphere.
17Rivers in the SeaCircular or elliptical currents are called gyres. They circulate clockwise in the Northern hemisphere and counter clockwise in the Southern hemisphere.The right or eastern sides of the gyres have cool currents and the left or western sides have warm currents. Suggest a reason for this.Cooler currents cool the air above them. Cool air holds less water vapour so the land close to these currents tend to be drier.Warmer currents hold more water vapour so the land close to them tends to have warmer air and more precipitation
18Rivers in the SeaThere is no complete current circling the Northern hemisphere because the continents get in the way.However, just north of Antarctica, the West Wind Drift encircles the world. It brings cold polar water and air to western parts of South America, Africa, and Australia.It is the largest surface current.
19Rivers in the SeaDeep ocean water is not affected by winds, however, there are slow moving currents in this water. Ocean water also moves vertically.Temperature and salinity affect ocean water.Cooler water is more dense than warmer water so it sinks below the warmer water.Salt water denser than fresh water so it sinks as well.
21The Great Ocean Conveyer Belt The largest continuous ocean currentReally thermo-haline circulation. Meaning?How does it work? See text p. 474Start at Greenland
22The Great Ocean Conveyer Belt Much of warm water from Gulf Stream & N. Atlantic Drift evaporates leaving behind saltier water. When it reaches Arctic O, it mixes with colder, saltier water and sinks to the bottom, heading south to Antarctica
23Great Ocean Conveyer Belt It turns east, splits into 2 branches-one heads to Indian O the other continues east. They join other currents and complete the circuit.Transit time is about 1000 a.Mechanism to transport nutrients and thermal energy from pole to pole.
24El NiñoCoastal upwellings arise when constant winds blow from the shore to the sea. Nutrients are brought up from the ocean bottom.Peruvian fishers named the warming phenomenon which arrived in December El Niño. It disrupted their fishing every few years.Arises from a reversal in the pattern of circulation of the trade winds and the upper level winds bringing warm water and rains to South America.Consequences include rains, flooding, typhoons, drought, fires etc
25Over Land and SeaDespite convection currents and the Coriolis Effect, large bodies of air can remain in almost the same location over a period of time. The air then takes on the characteristics of the land or water below i.e temperature and humidity. The body of air is called an air mass.They are classified as continental or maritime depending on where they form. They are also classed as polar or tropical (temperature-based).When these large masses begin to move or collide we get weather.
26Properties of Air Masses NameSymbolCharacteristicsContinental polarcPCool and dryMaritime polarmPCool and moistContinental tropicalcTWarm and dryMaritime tropicalmTWarm and moist
27Thanks for your attention Doc. www. wallpaperbase Thanks for your attention Doc!