Module 4Big cumulonimbus with big anvil It is important to..

Module 4Big cumulonimbus with big anvil It is important to..

Module 4Big cumulonimbus with big anvil It is important to comprehend

the forces that move the wind and the weather systems we experience. For example, if you are in the tropics, most weather comes from the east. If you are in the middle latitudes, most weather comes from the west. And lastly, if you are in the polar regions, most weather again comes from the east. All of this general motion is due to the forces directing the wind. In this discussion, you will talk about what causes these forces. Hot fluids rise. You know this by watching hot wax rise and contort in a lava lamp, or by observing bubbling chocolate in a pan while making fudge on a hot stove, or looking at a hot air balloon flow with the wind. The best weather example is a cumuliform cloud, most notably a cumulonimbus cloud. But what about general atmospheric motions? In this discussion, we will explore large-scale atmospheric flow across the earth. Instructions for this Discussion Activity Consider a column of air above a plot of ground. Let the column be rigid on its sides and bottom, but open at its top, resembling a very tall glass. Set the top of the column to the top of the troposphere, the level where the general trend in temperature stops decreasing with height. This is called the tropopause (Chapter 1), and is also the base of the stratosphere. So, air can move up freely in this column, and then will “spill over” and spread out at the top. Now, place this column at the equator where natural solar heating occurs. Hot air will rise in the column to near the tropopause where the temperature of the air in the column becomes equal to the temperature outside the column. The air at that height then will spread away from the column. Thus, the column will contain fewer air molecules. Answer two of the four following questions. In discussion with your classmates, respond to someone who answered different questions than you. Having a full understanding of all of these questions will help to prepare you for the Midterm Exam. 1. What is the effect(s) that fewer air molecules will have on the surface pressure of the column? Discuss what impact the rising air in the column at the equator will have on surface air slightly away from the equator. 2. Recall from the video on the Coriolis force how fast air at the equator is moving. What is the circumference of Earth? You may remember the answer: 25,000 miles. So, to an observer in space, air at the equator must be moving at the same speed as Earth’s surface is rotating, over 1,000 mph to make it around Earth in one day. Conversely, the “speed” of Earth’s rotation precisely at the North Pole takes a full 24 hours to spin once around a point. To that same observer in space, the speed of the air around that point (discounting the wind) is essentially 0 mph. So, as you move from the equator to the North Pole, the rotational speed of the ground decreases from a value in excess of 1,000 mph to 0 mph. With this in mind, discuss why people on the equator do not experience 1,000 mph winds. 3. What apparent path on the ground will air make if some of that faster moving air at the equator moves north to higher latitudes where the ground rotates slower? Or, similarly, what happens if some of that slower moving air at the North Pole moves south to lower latitudes where the ground rotates faster? Remember, we measure all wind motions with respect to Earth, a rotating sphere, not some imaginary flat and square surface. 4. What is the name of the regional surface winds along the north and south sides of the equator? State why they form with the directions they have.