The Dynamic Structure of the Atmosphere.pdf

Lesson 3 The Dynamic Structure of the Atmosphere Goal To familiarize you with the factors that affect atmospheric motion including atmospheric pressure, wind, frictional influences, fronts and air masses. To explain how topographical features such as land, water, and mountains affect air movement. Objectives Upon completing this lesson, you will be able to do the following: 1. Name and explain three forces that determine wind direction and speed within the earths friction layer. 2. Explain why wind speed changes with height and why this is important in air pollution studies. 3. Describe the effect that pressure systems have on the transport of air pollution. 4. Identify the two basic properties of an air mass. 5. Distinguish between four different types of fronts. 6. Explain the phenomenon called “frontal trapping.” 7. Explain how different types of terrain affect air flow and consequently air pollution dispersion. Introduction We are all familiar with the various forms atmospheric motion can take: gentle breezes, thunderstorms, and hurricanes, to name a few. Air moves in an attempt to equalize the air pressure imbalances that develop as a result of variations in insolation and differential heating. Differential heating is the main cause of atmospheric motion on the earth. This lesson will answer your questions about what causes the wind to blow from a certain direction and what causes the general global patterns of air circulation. You will learn how winds aloft behave differently from surface winds and how surface winds are influenced by the earth’s topography. Atmospheric Circulation Air moves in an attempt to equalize imbalances in pressure that result from differential heating of the earths surface. While moving from areas of high pressure to low pressure, wind is heavily influenced by the presence or absence of friction. Thus, surface winds behave differently than winds aloft due to frictional forces acting near the earths