Question

8. Explain how the movement of the convection fluid as it heated up relates to masses of heated air.

9. What do you expect will occur as air masses move over cold locations? Hot locations? Explain how this movement of air masses influence climate.

10. Describe how the qualities of air masses differ depending on whether they form over land or over an ocean.

11. What climate would regions where air masses from the equator and the poles collide probably have?

12. Carbon dioxide is a greenhouse gas that causes excess solar energy to be trapped in the form of heat in the atmosphere. Discuss how carbon dioxide may affect convection currents.

13. Although it is near the Atlantic Ocean, the northwest coast of Africa is characterized by hot, dry deserts. However, the Caribbean, at approximately the same latitude, possess a hot, moist climate and even supports rainforests. Using knowledge of the Coriolis Effect and air currents explain why this is true.

14. Describe how rising and sinking air (high and low pressure) in the atmosphere explains deserts near 30°N and 30°S.

15. Air in the troposphere is heated from the bottom up by heat given off by the surface of the earth. If the sun shines equally on Seattle (near water) and Bismarck, North Dakota, explain which would get hotter during the day.

Answer 1

8. Convection involves the transfer of heat through the movement of the medium’s particles. This medium must be a gas or liquid, thereby allowing for movement. Convection always transfers heat in the vertical plane. This movement is driven by variations in the medium’s density. As the air molecules are heated they gain energy and move apart thus decreasing the density and increasing the volume of the air mass. The decrease in density of air mass causes it to rise upward. As it cools, its density increases. Thus a convection current is formed when the cool dense air moves downward tiwards the source of heat, gets heated and less dense;then rises again and move away from source and again gets cooled.

9. The characteristics of an air mass depend on the region where it forms.When an air mass moves to a new region, it carries along its characteristic moisture and temperature. As the air moves over Earth’s surface, the characteristics of the surface begin to change the air mass. When air mass moves over cold locations, the air becomes cool as it loses energy to the cold land or water. Again if a continental polar air mass (cold air mass) moves over warm water, the air near the surface will become warmer and gain moisture. These changes begin where the air touches the surface. It may take days or weeks for the changes to spread upward through the entire air mass. An air mass that moves quickly may not change much.  

When a new air mass moves over an area, it is expected that the weather will change. Fronts is a boundary between air masses. The weather near a front can differ from the weather inside the rest of an air mass. As one air mass pushes another, some of the air at the boundary will be pushed upward. Clouds can form in this rising air. The weather often becomes cloudy or stormy as a front passes. Afterward, we experience the temperature and humidity of the air mass that has moved in.

10. Continental air masses form over land. Air becomes dry as it loses its moisture to the dry land below it.

Maritime air masses form over water. Air becomes moist as it gains water vapor from the water below it.

11. When two air masses collide, they tend to stay separate in the first instance, as oil remains separate from water. If a warm air mass from equator collides with a cool or cold mass from poles, it will ride gradually up and over it. The line which separates the warmer air from the cooler air is called a front and the front will rise from the ground at an angle with the warmer air above the cooler air. Normally, if it is warm air which approaches the cooler air the front will form a gentle angle and the warmer air will consequently rise gently upwards. However, if cooler air approaches and collides with warmer air, the heavy, denser cool air will tend to undercut the warmer air, pushing it rather like a bulldozer, forming a steeply rising front. When warm air is approaching cool air, the passing of the front will presage a rise in temperature as an observer passes from the cool mass to the warm mass, and consequently this is a warm front, marked with red semi-circles on a weather map.On the other hand, if cool air is approaching a warmer air mass the front will mark a fall in temperature and be called a cold front, marked with blue triangles on a weather map.

12. In the atmosphere, convection includes large- and small-scale rising and sinking of air masses and smaller air parcels. These vertical motions effectively distribute heat and moisture throughout the atmospheric column. The carbon dioxide and other gases in the atmosphere are virtually transparent to the visible radiation that delivers the sun's energy to the earth. But the earth in turn reradiates much of the energy in the invisible infrared region of the spectrum. This radiation is most intense at wavelengths very close to the principal absorption band (13 to 17 microns) of the carbon dioxide spectrum. When the carbon dioxide concentration is sufficiently high, even its weaker absorption bands become effective, and a greater amount of infrared radiation is absorbed. Because the carbon dioxide blanket prevents its escape into space, the trapped radiation warms up the atmosphere thereby disrupting the convection current in the atmosphere.Scientists fear that the increasing amounts of carbon dioxide could raise the Earth's surface temperature during the next century, bringing significant changes to worldwide weather patterns. Such changes may include a shift in climatic zones and the melting of the polar ice caps, which could raise the level of the world's oceans.

13. Though both Carribean islands and africa lise almost at the same latitude, the northwest coast of Africa is characterized by hot, dry deserts while the Caribbean, possess a hot, moist climate. This is beacuse of the trade winds. The trade winds are those that follow a wind pattern. This means the trade winds blow predominantly from one single direction over to a particular point. Such specific direction of trade winds arises due to earth's rotation.If the earth did not rotate, the wind current would go from the poles (high pressure) to the equator (low pressure).But as the earth rotate more quickly at the eaquator than at the poles, the wind is deflected towards the right in the Northern Hemisphere and towards the left in the Southern Hemisphere. This deflection is called Coriolis Effect. Due to this Coriolis effect, the moisture laden trade winds reaches the Carribean thus supporting rainforest while the west coast of Africa remains hot and dry.

14.  At 30 degrees North and South latitude the air is cooling, becoming more dense and sinking. Sinking air creates high pressure.So the high pressure along this belt is due to subsidence of air coming from the equatorial region which descends after becoming heavy. The subsiding air is warm and dry, therefore, most of the deserts are present along this belt, in both hemispheres.Global winds are caused by the constant balancing act going on in our atmosphere as moist, warm air travels upward from the Equator and then cools and sinks at the 30 degree latitude belt. The air rises again at the 60 latitude and sinks at the poles. When the air moves laterally across the Earth's surface from belt to belt (High to Low pressure) it creates winds.

15. During day, if sun shines equally on water and sand, sand gets heated more quickly. Thus Bismarck, North Dakota would get hotter.