1-3: Atmospheric Structure and Circulation

Objectives

• To understand how shortwave and longwave radiation create differential patterns of heating and cooling and establish the vertical and horizontal patterns of atmospheric temperature and pressure.
• To understand the time and space scales and flow patterns that constitute the circulation of the global atmosphere.

Pre-Class Preparation

Procedure

1. Read the summary information.

   Class images

2. Print for offline review

3. Take the summary information quiz. Quizzes are available from your portfolio.

Online and Class Discussion

• Social Comments
• Knowledge-building Comments
• Ethical Comments

• Unit Problem to Ponder
• Unit exam questions from previous years
• Unit discussions from previous years

Unit Wrap-up Materials

• Group Discussion Summary:

  Group members preparing summary: Kurtis Cecil, Nathan Ohrt, Lori Schmitz, Daniel Pollock

  Online Summary Information

  Learning Unit 1-3 introduces the basic characteristics of atmospheric structure and circulation. The earth/atmosphere/ocean system takes energy from the sun, converts it to many other forms, and then releases it back to outer space. More energy from the sun is absorbed in low latitudes in the tropical regions and subtropics. It is then transmitted toward polar regions before being radiated back to outer space. This energy is transmitted by warm ocean currents and global atmospheric circulation, where warm air from the tropics rises, moves toward the poles, and is replaced by cooler air from higher latitudes. As the warm air rises in the tropics, it cools, and the moisture precipitates out, making the air very dry. This air then sinks (and is warmed) in the high pressure belts around 30 degrees north and 60 degrees south which results in deserts in these regions of the earth.

  Global warming is thought to be a change in the redistribution of energy in the atmosphere, not a gain of energy. When the gas composition of the atmosphere is changed, the surface is warmed, but the stratosphere actually cools.

  There is both a vertical and latitudinal temperature structure to the atmosphere. The continental land masses are warmer than the oceans in summer and cooler in winter. A global plot of isotherms demonstrated this by showing that isotherms over the continents move toward the poles in summer. Vertical temperature structure of the atmosphere affects how moisture, pollutants and trace gases are distributed throughout the atmosphere. Moisture, pollutants, or trace gases that are put into the atmosphere at the surface are usually mixed quite thoroughly throughout the troposphere within a matter of 2 or 3 days. The stratosphere (upper atmosphere) is a very stable region where pollutants and trace gases don't mix well.

  Regional precipitation patterns are not necessarily linked to the global circulation patterns. The effect of changes as a result of global warming, and impacts on agriculture and natural systems are therefore very uncertain.

  References for this unit include websites sponsored by UCAR, NOAA, UN Food and Agriculture Organization, Iowa State and other universities, National Weather Service, and others. These websites address weather, climate, drought, meteorology, and societal and global food issues.

  Online Discussion

  Online discussion consisted of two comments, one of which was responded to. One student was confused about how the isotherms shifted during different seasons and why the isotherms follow the lines of latitude more closely in the southern hemisphere. A responder explained why the isotherms move toward the poles in summer, and also offered a possible explanation (less land mass) for the isotherm phenomenon. The second commentor was curious as to whether or not the atmospheric air flows has changed over time.

  Lecture Materials

  Lecture material for this unit, presented on 1/12/01, focused on transformation of shortwave to infrared radiation, absorption at the earth's surface, pressure gradients, and the various greenhouse gases in the atmosphere.