Atmospheric Sciences 171, Section 2

Atmospheric Sciences 171
NOTES

These notes are not meant to be a substitute for attending class and taking notes. Rather, they should be used to supplement and clarify the day's lecture material.

General Resources:

USA2day

Online Guides: instructional modules and curriculum

Geography 101: Home Page (Lemke)

Fundamentals of Physical Geography

Jan. 12

Reading: Pages 1-13 & Look at Appendix A, especially the powers of ten.

Jan. 14

Composition of the atmosphere: The atmosphere is the thin envelope of a mixture of gases, liquid droplets and solid particles that surrounds the Earth. Nearly all of the mixture is made of gases. Of the gases, nearly 99% are nitrogen and oxygen molecules. We will divide the gases into two classes; permanent and trace gases. Permanent gases occur in the same proportion in the atmosphere just about everywhere in the atmosphere, whereas trace gases occur in different proportions.

Permanent Gases: N2, O2, Ar

Atmospheric CO2 measurements

Atmospheric water vapor

Ozone

Jan. 19

We can get a feel for the spatial variation of water vapor in the atmosphere using satellite images pasted together to show the global picture. Each image shows regions of the atmosphere that have very little water vapor (the dark regions) and those that have a good deal of water vapor (the brighter areas).

Dew Point Temperature is related to the concentration of water vapor in the air. The larger the dew point, the larger the concentration of water vapor. The following map of dew point across the U.S. shows in general that the dew point is lower in the interior region of the country and higher near the coasts. This is a result of the main source of atmospheric water vapor being evaporation from large bodies of liquid water such as oceans and lakes. However, this general picture can be changed by weather events. For example, notice the region of very low dew points in Canada, north of the Great Lakes region. This is associated with very cold air in this region.

Jan. 21

Reading: Pages 381-386.

Selective scattering of light by air molecules (blue light scattered more efficiently than red light) causes the sky to look blue to our eyes during the day. This also means that when the sun's rays pass through the atmosphere more blue light is scattered and removed than is red light. So, when the sun sets and the rays of the sun travel a long distance in the atmosphere, what finally gets to our eyes is more red light than blue light although the sun light that entered the top of the atmosphere had about the same amount of blue and red light.

The atmosphere also causes the sun's rays to refracted or bent slightly. Whenever light travels from a media of one density to a media of another density, the path is slightly bent. This allows solar rays that would otherwise just pass by the earth and not strike the moon to instead be bent slightly by the earth's atmosphere so that they do strike the moon. The light that strikes the moon is not white, but instead more red due to the filtering process of the atmosphere mentioned above.