Distribution of solar energy Ocean Currents The Department of Geography Part of the Faculty of Social Subjects St. Mungo’s AcademyGeography HomeSearch

Distribution of solar energy

Ocean Currents

The Department of Geography

Part of the Faculty of Social Subjects

St. Mungo’s Academy Geography Home Search

World air masses

Changing Climates

Planetary Wind Systems

ITCZ

AtmosphereThe Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly (by molar content/volume) 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, trace amounts of other gases, and a variable amount (average around 1%) of water vapor.

The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.

There is no definite boundary between the atmosphere and outer space. It slowly becomes thinner and fades into space.

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Ocean Currents




World air masses

Changing Climates


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The distribution of the suns energy is not equal around the earth. Places that are near to the equator are much warmer than places that are nearer the poles. This is due to curvature of the earth, the angle of the sun in the sky and the layer of atmosphere which surrounds the earth.

Click here to see the distribution of the suns energy





Ocean Currents




World air masses

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ITCZ

Earth Sun

Spread out

Even more spread out

Concentrated

1 2 3

1: The atmosphere of the earth

2. Rays are spread out and have to pass through a lot of atmosphere

3. Very concentrated and only pass through a little atmosphere





Ocean Currents




World air masses

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Across the equator the sun is strong and hot

At the poles the sun passes through a lot of atmosphere and much of it is reflected by the ice




Ocean Currents




World air masses

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When the sun eventually reaches the earths atmosphere, not all of it reaches the earth: in fact only 46% is absorbed by the planet.The rest is either reflected or absorbed by other materials:• 19% is absorbed by dust in the atmosphere• 8% is dispersed through the atmosphere• 4% is absorbed by clouds• 17% is reflected by the clouds• 6% is reflected by the earths surface: ice, snow etc

Click here to see this in picture form





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absorbed by clouds and dust, water vapour and other gases in the atmosphere

absorbed by surface

reflected by clouds and dust, water vapour

and other gases in the atmosphere

reflected by surface

100%

23%

25%

52% 6%

46%




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Wind pressure beltsWind is the movement of air, principally horizontally cause by the earths rotation and the earths tilt.The basic reason that the earths atmosphere is always in motion is that more of the suns heat is received at the equator than near the poles. This unequal heating gives rise to convection currents. The heated air near the equator becomes lighter, rises and expands. High up, the air spreads outwards in the direction of both poles. As it gradually cools, it becomes heavier and eventually sinks. This cool, descending air flows back towards the equator and completes the cycle of convection. This is known as the Hadley cell.




Ocean Currents




World air masses

Changing Climates


ITCZ




Ocean Currents




World air masses

Changing Climates


ITCZ

The Polar cell is the northernmost cell of circulation and its position is between 60°N and the North Pole. At the pole, cold, dense air descends, causing an area of high pressure. As the air sinks, it begins spreading southward. Since the Coriolis force is strongest at the poles, the southward moving air deflects sharply to the right. Near 60ºN, the southeasterly moving air moving along the surface collides with the weak, northwesterly surface flow that resulted from spreading air at 30°N. This colliding air rises, creating a belt of low pressure near 60°N

Wind pressure belts




Ocean Currents




World air masses

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ITCZ




Ocean Currents




World air masses

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Wind pressure beltsThe mid-latitude circulation cell between the Polar cell and the Hadley cell is called the Ferrel cell. It is believed the cell is a forced phenomena, induced by interaction between the other two cells. The stronger downward vertical motion and surface convergence at 30°N coupled with surface convergence and net upward vertical motion at 60°N induces the circulation of the Ferrel cell. This net circulation pattern is greatly upset by the exchange of polar air moving southward and tropical air moving northward. This best explains why the mid-latitudes experience the widest range of weather types.




Ocean Currents




World air masses

Changing Climates


ITCZ




Ocean Currents




World air masses

Changing Climates


ITCZ

ITCZ – Intertropical convergence zone

The Intertropical Convergence Zone (ITCZ) is a belt of low pressure around Earth at the equator. It is formed by the vertical ascent of warm, moist air from the latitudes above and below the equator.The air is drawn into the ITCZ by the action of the Hadley cell. It is transported by the convective activity of thunderstorms; regions in the ITCZ receive precipitation more than 200 days in a year.The migration of the inter-tropical convergence zone (ITCZ) in Africa affects seasonal precipitation patterns across that continent.




Ocean Currents




World air masses

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ITCZ – intertropical convergence zone




Ocean Currents




World air masses

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ITCZ

ITCZ – intertropical Convergence zone

The blue shading on the map correspond to the average monthly position of the ITCZ.




Ocean Currents




World air masses

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ITCZ




Ocean Currents




World air masses

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World air massesAn Air Mass is a large volume of air which travels from one area to another. The weather an air mass brings is determined by the region it has come from and the type of surface it has moved over.




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Tropical Air (T):

Continental tropical (cT)Continental tropical (cT):: Hot and very dry, originating from the arid and desert regions during summer. The least common air mass to affect the British weather. However, approaching from the south and south-east in summer it can bring record heat to southeast Britain.Maritime tropical (mT)Maritime tropical (mT).. Mild and damp in winter, very warm and muggy during summer. Originating from the Azores this air mass approaches the British Isles from the west, leading to overcast skies with prolonged rain In summer tropical maritime air often produces warm weather with abundant sunshine in the southeast.

World air masses




Ocean Currents




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Polar Air (P):

Continental polar (cP)Continental polar (cP):: Cold and dry, originating from high latitudes, typically as air flowing out of the polar highs. This air mass often brings cold, dry and clear weather on a perfect winter day and also dry and warm weather on a pleasant day in summer.

Maritime polar (mP)Maritime polar (mP):: Cool and moist, often originating as continental polar air over the North American and Asian land masses and is modified as it moves out over the Atlantic and Pacific Oceans. Heated by the relatively warm water bodies this air mass becomes rather unstable resulting in blustery showers over the sea and windward coasts.

World air masses




Ocean Currents




World air masses

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World air massesArctic Air (A):

Continental arctic (cA)Continental arctic (cA):: Extremely cold temperatures and very little moisture. Originating over the Arctic ocean in winter, when high pressure dominates and differs only slightly from the continental polar (cP) air masses that develop over Siberia and northern Canada.

Maritime arctic (mA)Maritime arctic (mA):: From the same source region, but less dry and less cold - in a way less extreme.




Ocean Currents




World air masses

Changing Climates


ITCZ

World air masses




Ocean Currents




World air masses

Changing Climates


ITCZ




Ocean Currents




World air masses

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Ocean currentsOcean currents are movements of surface water. How the world's oceans move has a huge influence on our climate and it, in turn, is influenced by a number of factors.

Like atmospheric circulation, ocean currents help to redistribute energy across the earth. Because they cover 67% of the earth's surface, the oceans receive 67% of the sun's energy that reaches earth. The ocean holds on to this heat for longer than the earth does and the ocean currents move this heat around, from the tropics to higher latitudes. In total, ocean currents transfer about 25% of the global heat budget.




Ocean Currents




World air masses

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Warm Currents(flow away from the equator)

Cold Currents(flow towards the equator)




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These patterns can be explained by a number of factors:•The prevailing winds on the surface create friction with the surface water, setting up the ocean currents. •The huge size of the Atlantic and Pacific oceans allows these patterns to form. •The trade winds drive the pattern between 0 and 30 degrees north and south and the westerlies create the pattern between 30 and 60 degrees north and south. •Uneven heating produces density differences in the oceans. •Cold dense polar air sinks, then spreads towards the equator where it pushes up the less dense warmer water which moves off towards the polar areas.

Ocean currents




Ocean Currents




World air masses

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Changing climates: global warming

Global warming refers to an average increase in the Earth's temperature, which in turn causes changes in climate. A warmer Earth may lead to changes in rainfall patterns, a rise in sea level, and a wide range of impacts on plants, wildlife, and humans.




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Physical causes of global warming and cooling include:•Variations in solar energy - sunspot activity raises global temperature •Volcanic eruptions - large quantities of volcanic dust in the atmosphere shield the earth from incoming insolation, lowering global temperature. For example, the eruption of Mount Pinatubo in 1991 caused a dip in global temperatures in the early 1990s.





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World air masses

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•Changing oceanic circulation such as the periodic warming (El Nino) and cooling (La Nina) of areas of the tropical Pacific Ocean These physical causes of global temperature change have always existed and have been responsible for alternate heating and cooling cycles of the earth's temperature.

However, it is human factors that are causing the most controversy…





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The human causes of global warming have been in the news a lot in recent years - you can probably think of a few examples. Human factors are the result of growing population and economic developments.

They include:•the burning of fossil fuels for transport, industry and power, producing carbon dioxide •world-wide deforestation, sometimes involving rainforest burning, which also produces carbon dioxide.





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•car exhausts and nitrogen fertilisers, producing nitrous oxide •CFCs found in fridges, air conditioning and aerosols and as a bi-product of the production of polystyrene packaging, like pizza and burger boxes •methane, produced from rice fields, landfill sites and from both ends of cattle These different greenhouse gases - carbon dioxide, methane, nitrous oxide - have caused an enhanced greenhouse effect, trapping some outgoing infra-red radiation and keeping the earth warmer than it might otherwise be.




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Distribution of solar energy Ocean Currents The Department of Geography Part of the Faculty of Social Subjects St. Mungo’s AcademyGeography HomeSearch