What is wind? Moving air... Friday, 21 November, 14

Transcription

1 What is wind? Moving air...

2 Why does air move? To create atmospheric equilibrium

3 There are always regions of high air pressure and regions of low air pressure on in the troposphere.

4 Or......to fill in the vacuum created by a lower pressure region... like water rushing down hill to fill in a depression in the ground. To

5 How is air pressure is measured? Imagine a "unit area" of 1 square inch. At sea level, the weight of the air above this unit area would (on average) weigh 14.7 pounds! That means pressure applied by this air on the unit area would be 14.7 pounds per square inch. Meteorologists use a metric unit for pressure called a millibar and the average pressure at sea level is millibars.

6 How Air pressure is measured Average atmospheric pressure = mb at sea level when 15 Average atmospheric pressure at sea level is: 30 inches Pa kpa mbar

7 195 mph or

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9 Severe Typhoons Wind Name Year speed mb Landfall mph Nancy km/hr Violet km/hr Haiyan km/hr Killed 192 ppl in Japan Killed 2 in Japan Killed in Philippines Kit Did not make landfall

10 Film Photo from Knapp needs copying or just use map?

11 Read p. 76, 79 & 80

12 Atmosphere quiz a. Name the 4 atmospheric layers. b. Which is the layer where all weather occurs? c. For how many kilometers does this layer (question b) extend above the lithosphere? d. What is the lapse rate? e. In which 2 layers does air temperature increase with altitude? f. Does air pressure increase or decrease with elevation? g. What are the 3 main gases in the lower atmosphere? h. What is insolation? i. What is albedo?

13 Atmospheric Circulation

14 Atmospheric Circulation Atmospheric Circulation equator Air is always rising near the due to the direct radiation of the sun at that location. This air, after it has risen, flows towards the North Pole in the Northern Hemisphere and towards the South Pole in the Southern Hemisphere. On the way to the poles this air cools, and therefore descends at 30 about the degree latitudes (north and south hemisphere). This descending air bunches up at these locations permanent high pressure forming the regions.

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16 Underneath these high pressure region are where most the deserts world s are located. Each polar region high is also a region of pressure. The only low region with permanent pressure is the equator belt of air near the. This low pressure region moves seasonally with the overhead noon sun.

17 Due to the rising air in the equatorial region, a constant low pressure at ground level acts as a vacuum for the trade winds. These trade winds are known as the north-easterlies in the northern hemisphere and south easterlies in the southern hemisphere. Winds are named after the direction from which they come. The coriolis force causes these trade winds to be deflected to the in the northern hemisphere and to right the left in the southern. These trade winds from the north and south meet near the equator in an area known as the. Intertropical convergence zone (ITCZ) This area is characterized by convectional rain and calm winds.

18 The prevailing are the winds we experience in southern Canada and most the USA. These winds move away from the Equator and are deflected to the right (hence Westerlies) because of the Coriolis force. * westerlies

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20 Seasonal Changes of direct solar energy

21 The World s Weather Heating is not always greatest at the Equator. The zone of maximum heating moves as the overhead noon sun changes in latitude with the seasons. Seasonal changes in mid-latitude countries such as Canada slow changing average temperatures involve /cause between summer and winter. Because depressions (low pressure systems) are moving across our region all year long we do not have one wet season and one dry season as they do in some tropical areas.

22 In some regions, a dry season can be entirely rainless with temperatures always above 30º C. This drastically affects vegetation and animal life. This would occur in areas under permanent high pressure. Other tropical regions experience gradual or even sudden changes to a rainy season. These are called the monsoon climates. There is a distinct dry and a rainy distinct season.

23 Follow the Sun... Look at the photo provided for you. A location of 10 degrees North (Example X) is under air, therefore experiences drought conditions in and under rising air, therefore convectional conditions by July. This wet and dry season contrasts is what is called a climate. It is typical of much of the tropics. monsoon sinking January rain Station Z at 25 degrees north is always under sinking air desert therefore experiences a climate.

24 equator Station Y is at the and is therefore under a band of rising air most of the year. As a result it experiences convectional rain every month. Combined with very warm temperatures these conditions result in the beautiful tropical rainforests of Southeast Asia, South America and the Congo. See map...

25 Now... it s definition time...