§ 32. Winds (textbook)

§ 32. Winds


1. Recall of course natural that such wind.

2. What serves as a weathervane?


Formation wind. Although air and invisible to the eye, we always feel his movement - wind. The main cause of wind is difference in atmospheric pressure over the area of surface. It is only pressure where a decrease or increase, as the air will travel from place to more pressure toward smaller. A pressure balance is disturbed uneven heating different parts of the earth's surface from which the different heating and air.

Try to imagine this in the example wind that occurs on coasts and seas is called breeze. Lots of land surface - dry land and water - heated unequally. Sukhodil heats up faster. Therefore, the air above it heats up quickly. It rise up, the pressure decreases. Over the sea at this time and colder air under higher pressure. Because air moves from the sea on dry land in place warm. That wind blew - daily breeze. At night everything is the opposite: dry land cools faster than water. Over it cold air creates more pressure. And over the water that lingers long and warm cooled slowly, the pressure will be lower. Colder air from the land of high pressure area moves towards the sea where the pressure is less. There Night Breeze.

Thus, the difference in atmospheric pressure acts as a force that causes horizontal movement of air from high pressure region to the low pressure. So wind is born.

Determination direction and wind speed. Determine wind direction after this side of the horizon, where it blows. For example, if the wind is blowing from event, it is called Western. This means that air moves from west to the east.

Wind speed depends on atmospheric pressure: the greater difference in pressure between areas of the earth surface, the stronger the wind. It measured in meters per second. Near Earth's surface winds often blow from the speed 4.8 m / sec. In the old days, when there were no devices, speed and strength determined by local wind characteristics: at sea - by the action of wind on the water and sail vessels on land - on the tops of trees, a deviation from the smoke pipe. In many features was developed 12-point scale. It allows you to determine the strength of the wind points and then his speed. If there is no wind, that is his strength and speed zero, it calm. Wind power in the 1 point that almost the former trees, called quiet. Next scale: 4 points - moderate wind (5 m / s), 6 points - strong wind (10 m / s), 9 points - storm (18 m / s), 12 points - hurricane (Over 29 m / s). At the weather station and force determine wind direction by weathercock, and speed - Anemometer.

The strongest winds near Earth's surface blowing in Antarctica: 87 m / s (separate gusts reached 90 m / s). The highest wind speed recorded in Ukraine in Crimea Mount Ai-Petri - 50 m / sec.

Rose winds. Windrose- A peculiar  schedule. He clearly shows repeats winds of different directions by time (month, year). Build it well: hold the line directions of the parties horizon. Calculates how many days during the month was from the north wind, South and others. At the appropriate lines from the center lay number of segments-days with winds in this direction. For example, conventionally one day take by 0.5 cm segment north wind blew If within six days then the line from the north lay six pieces of 0,5 cm (6 x 0,5 cm = 3 cm) if northwest blew 4 days, then the line from north-west lay two cm, etc. The points indicated on the lines connecting consecutively. The center picture circle, which record the number of days without wind.


Fig. Windrose


Variable and constant winds. Variable winds change their direction. These are already known to you breezes (with French "Breeze" - a light wind). They change their direction twice a day (Day and night). Breezes is not only on the seaside  seas, but also on the shores of large lakes and rivers. However, they cover only a narrow strip of coast, penetrating deep into the land or sea for several kilometers.

Monsoon formed as well as the breezes. But they change their direction twice per year in each season (summer and winter). In Arabic, "monsoon" means "Season". In summer, when air over the ocean is heated slowly and the pressure on him greater moist marine air penetrates on land. It is - summer monsoon, which is the daily thunderstorm rainfall. And in winter, when high pressure air is set over the dry winter monsoon begins to act. It blows from the land towards the ocean and brings  cold dry weather. Thus, cause the formation of monsoons are not daily and seasonal fluctuations in air temperature and atmospheric pressure over land and ocean. Monsoon to penetrate and dry ocean for hundreds and thousands of kilometers. They are especially common in southeast coast of Eurasia.

Unlike variables, constant winds blowing in one direction during the year. Their formation associated with zones of high and low pressure on Earth.

Passat - Winds that blow throughout the year from zones of high pressure near 30's tropical latitudes of each hemisphere to the waist low pressure at the equator. Under the influence of Earth's rotation around the axis they are not addressed directly to the equator, and rejected, and blowing from the north-east in Northern Hemisphere and the south-east - in the South. Trade winds, different uniform amazing speed and stability, were favorite winds seafarers.

Of tropical zones of high pressure winds blow not only to the equator, but in opposite direction - toward 60's latitude low pressure. Under the influence of deflective force Earth's rotation with distance from tropical latitudes they gradually declined to the east. Yes there is air moving from west to east and these winds temperate latitudes are Western.


FAQ task

1. What causes the formation of the wind?

2. Winter on the coast of pressure was 770 mm рт. Art. and the sea - 765 mm рт. Art. In which direction will the wind blow?

3. With devices which determine the direction, power and wind speed?

4. What is the force of the wind?

5. Why trade winds and westerlies called persistent winds? How are they formed?

6. Under the influence of constant wind which is Ukraine?

7. In the season you can go on with sailing China to Japan?

8. Explain the formation of daily breeze on a logical chain: the uneven temperature