Thursday Jan. 17, 2008

The first day of class.  We first briefly discussed the Course Information handout.  Read through this carefully on your own.  Note the various options you have for purchasing a copy of the course textbook.  You should try to purchase a copy of the photocopied Classnotes (in the bookstore) right away as we will probably be using some of them in class next Tuesday.

Next we looked at the Writing Requirements handout.  You should be thinking about which of the 4 experiments (or book or scientific paper reports) you would like to do so that you can sign up in class next Tuesday.  Distribution of the materials for the first experiment will probably also begin in class on Tuesday.
Your grade in this class will depend on your quiz scores, how much extra credit you earn, your writing grade, and (perhaps) your score on the final exam.  A sample grade report from the Fall 2007 T Th Nats 101 class was shown.

Doe_J
quiz1 -49 (160 pts possible) 69.4%
quiz2 -45 (175 pts possible) 76.5%
quiz3 -53 (180 pts possible) 70.6%
quiz4 -53 (185 pts possible) 71.4%

1.7 EC points (4.0 pts possible)
writing scores: 34.0 (expt/book report) + 45.0 (1S1P pts)
writing grade: 98.8%
average (no quiz scores dropped): 77.3% + 1.7 = 79.0%
average (lowest quiz score dropped): 79.3% + 1.7 = 81.0
you DO need to take the final exam
-26.0 pts missed on the final exam = 79.6%
3Q&W>F overall average is 80.7

Don't worry about all the details at this point.  This student earned a B in the class despite having low Cs even a D on the quizzes and a C+ on the final exam.  This is due largely to the high writing grade.  The writing and the optional extra credit homework assignments can really help raise your overall grade.

We'll begin this new semester in Chapter 1 of the text.  Before opening the book and beginning the first reading assignment, try to imagine what you would put in the first chapter of a meteorology and climatology textbook.


Student answers to the question above included:  whether there was enough oxygen in the outside air to breathe, temperature of the outside air, and gravity.  These and other basic characteristics of the atmosphere such as air pressure and air density are covered in Chapter 1.

 Today we were mostly just concerned with the composition of the earth's atmosphere, in particular the 5 most abundant gases in the earth's atmosphere.


This is the first of several questions asked during class.  It was an anonymous survey. 
Some of this material, in liquid form, was poured into a styrofoam cup.


The correct answer is nitrogen (you can fill in the blank in Question 1a and in the figure above with the word nitrogen).  You can see liquid nitrogen, it is clear (not blue as shown above) and looks like water.  Once it has evaporated and turned into a gas it is invisible.  Nitrogen was discovered in 1772 by  Daniel Rutherford (a Scottish botanist).  Atmospheric nitrogen is relatively unreactive and is sometimes used to replace air in packaged foods to preserve freshness. 


Here's the same question plus an additional question.  Multiple choice questions like this might be easier to answer than a fill-in-the-blank question.  

Fill in the first blank with nitrogen; oxygen goes in the 2nd blank.  Oxygen is the second most abundant gas in the atmosphere.  Oxygen is the most abundant element (by mass) in the earth's crust, in ocean water, and in the human body.   Here's a photograph of liquid oxygen.  It really does have a blue (light blue) color.

When heated (such as in an automobile engine) the oxygen and nitrogen in air react to form compounds such as nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O).  Together as a group these are called oxides of nitrogen; the first two are air pollutants, the last is a greenhouse gas. 

The 5 most abundant gases in the atmosphere were listed.

Water vapor and argon are the 3rd and 4th most abundant gases in the atmosphere.  The concentration of water vapor can vary from near 0% to as high as 3% or 4%.  Water is, in many locations, the 3rd most abundant gas in air.  In Tucson, the air is often dry enough that argon is in 3rd position and water vapor is 4th.

Water vapor, a gas, is invisible.  Clouds are visible because they are made up of small drops of liquid water or ice crystals.  Water is the only compound that exists naturally in solid, liquid, and gaseous phases in the atmosphere.

Argon is an unreactive noble gas (helium, neon, krypton, xenon, and radon are also inert gases).  Noble bases are often used in "neon signs."


The answer to this question is water vapor.

Water plays an important role in the formation of clouds, storms, and weather.  Meteorologists are very interested in knowing and keeping track of how much water vapor is in the air at a particular place and time.  One of the variables they use is the dew point temperature; it has two "jobs."
 

Its first job is to provide a measure of the amount of water vapor in the air. The dew point is just a number.  When the value is low the air doesn't contain much moisture.  The higher the dew point value, the more water vapor there is in the air.

The chart below gives a rough equivalence between dew point temperature and percentage concentration of water vapor in the air.


Click here to see current dew point temperatures across the U.S. 

The dew point in Tucson this morning was 2o F.  This is very low, the air is currently very dry.  Even drier air can be found in the "4 Corners" area where dew points of -10o F, even -20o F are being observed.

The second job of the dew point temperature is illustrated below.  When you cool moist air to its dew point, the relative humidity becomes 100% and a cloud forms.


We will cover each of the topics a-d below at the beginning of this semester.  This is an election year and Arizona's presidential primary election is Feb. 5, part of "super Tuesday."  In that spirit the class will decide which topic to cover first.  You'll learn the results in class on Tuesday.


The following information was covered quickly at the end of class.  There will often be a little bit of extra material at the end of the online class notes that wasn't covered in class.  So even if you come to class and take good notes it would be a good idea to look through the online notes to see if they don't contain some extra material. 

The earth's first atmosphere was composed mainly of hydrogen and helium.  These light-weight gases escaped into space and were lost.  The next atmosphere was built up of gases emitted during volcanic eruptions, mostly water vapor, carbon dioxide, and nitrogen.  As the earth began to cool the water vapor condensed and began to create oceans.  Carbon dioxide dissolved in the oceans and was slowly turned into rock.  Much of the nitrogen remained in the atmosphere.


Volcanoes didn't add any of the oxygen that is the atmosphere.  Where did that come from?

The oxygen is thought to have first come from photodissociation of water vapor and carbon dioxide by ultraviolet light (the high energy radiation splits the H20 and CO2 molecules into pieces).  The O and OH react to form O2 and H.

Once O2 begins to accumulate in the air it can react with O to form ozone, O3. The ozone then begins to absorb ultraviolet light and life forms can safely move from the oceans (which would absorb UV light in the absence of ozone) onto land.  Eventually plants and photosynthesis would become the main source of atmospheric oxygen.

You don't need to remember all the details of the chemical equations above.  Remember that the buildup of oxygen was a two-step process (photodissociation was involved in the first step, plants and photosynthesis in the 2nd step).  Remember that ultraviolet light (UV light) is dangerous high energy stuff that can break molecules into smaller pieces and can cause skin cancer.  Remember that once oxygen began to buildup up in the atmosphere, ozone could form.  Ozone absorbs UV light and protects people and plants living on the ground.