Friday, 21 November 2014

The sun and the temperature

The sun causes all our weather because it heats the earth unevenly. The contrast between the hot parts and the cold parts of the earth turns our atmosphere into a powerful engine. The engine keeps cold and warm air moving and makes changes in air pressure. Those air pressure changes cause wind. The heat of the sun also helps moisture to rise and form clouds, bringing rain, snow, or thunderstorms. So all the changes in our weather come, at least indirectly from the sun. For more on the summer sun, go here.

Blanket of Air
As the sun warms up the earth, the ground absorbs the heat, and reflects some of it back into the air. That's one reason why it's usually warmer near the ground and cooler on the higher hills and mountains. The atmosphere acts like a big blanket over the earth, holding in the warmth and reflecting it back to earth


TASK

Explain the text with your words. No use the translator, you can search for the meaning of what you do not know, but explain it, with your words.

  • Why is so important the sun?

  • how the sun created the climate zones?

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Wednesday, 19 November 2014

Atmospheric Circulation

Atmospheric Circulation One way to accomplish the transfer of heat from the equator to the poles would be to have a single circulation cell that was upward in the tropics, poleward aloft, downward at the poles, and equatorward at the surface. This is the single-cell circulation model first proposed by Hadley in the 1700’s.

Since the earth rotates, the axis is tilted, and there is more land mass in the northern hemisphere than in the southern hemisphere, the actual global pattern is much more complicated. Instead of a single-cell circulation the global circulation model consists of three cells for both N and S hemispheres. These three cells are the tropical cell (also called a Hadley cell), the midlatitude cell and the polar cell.
Surface Features of the Global Atmospheric Circulation System
Main wind belts:
Because the Coriolis force act to the right of the flow (in the Northern Hemisphere), the flow around the 3-cells is deflected. This gives rise to the three main wind belts in each hemisphere at the surface:
· The easterly trade winds in the tropics
· The prevailing westerlies
· The polar easterlies
Doldrums, ITCZ:The doldrums are the region near the equator where the trade winds from each hemisphere meet. This is also where you find the intertropical convergence zone (ITCZ). It is characterized by hot, humid weather with light winds, major tropical rain forests found in this zone. Migrates north in January and south in July.
Horse latitudes:The horse latitudes are the region between the trade winds and the prevailing westerlies. In this region the winds are often light or calm, and were so-named because ships would often half to throw their horses overboard due to lack of feed and water.
Polar font:The polar front lies between the polar easterlies and the prevailing westerlies.
Pressure belts:
The three-cell circulation model would have associated with it the following pressure belts:
· Equatorial low – A belt of low pressure associated with the rising air in the ITCZ. (The rising of warm air heated at the Equator causes an area of low pressure called Equatorial Low. As the air rises, creates clouds and precipitation.)
· Subtropical high – A belt of high pressure associated with the sinking air of the horse latitudes. (At the subtropics the air cools and descends creating areas of high pressure with clear skies and little precipitation, called the Subtropical High. The descending air is warm and dry, and produces deserts in these regions.)
· Subpolar low – A belt of low pressure associated with the polar front.
· Polar high – A high pressure associated with the cold, dense air of the polar regions.To learn more.

HOMEWORK:
  1. What is the main idea in this text?
  2. Explain the Atmospheric circulation.
  3. What number of the atmospheric cells are in the Earth ? Explain

Friday, 7 November 2014

What is Drought?

What do you think when you hear the word drought? Do you think “dry,” “hot,” “dusty,” or “cracked earth,” or even “no water”? If so, you’re on the right track!
When a place is in a drought, it is dry and hot, often dusty; cracks may appear in the soil, and rivers, lakes, streams, and other sources of water can go dry. A drought means that a place has less precipitation (rain or snow) than normal over a few months or even longer.
What causes this? How does drought really affect us? How can we be prepared for drought? These are all important questions that we will answer as we explore drought.

What causes a drought? 
How Does Drought Affect Our Lives?

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