Friday Jan. 14, 2011
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Welcome to NATS 101 - Introduction to Weather and Climate.

I liked Aaron Copland's Fanfare for the Common Man that was played at the beginning of Wednesday's memorial ceremony at McKale Center (I wasn't there unfortunately, but I watched it on TV).  I selected a different version by Emerson, Lake, and Palmer to play before class today.  For the last couple of years I have been filling the few minutes before class with some kind of music, often local talent.  Music won't ordinarily take up any actual class time.  Hopefully you'll like at least some of the selections.  Comments and ideas from students are welcome (I got well over 100 suggestions from students in my two sections last fall). 

Today was the first day of class.  We first briefly discussed the Course Information handout.  Please read through that information carefully and let me know if you have any questions.

A textbook is not required for this class.  If you want to get a more complete picture of the subject than we will have time to do in class, you might want to purchase one of the textbooks that are being used in the other NATS 101 sections.  Or if you'd like to borrow one of the copies of introductory level textbooks that I have in my office, you'd be welcome to do so.  Otherwise you should be able to do perfectly well in the class by reading the online notes and other suggested online sources. 

A set of photocopied ClassNotes (available in the Student Union Bookstore) is required.  You should try to purchase a copy as soon as you can because we will probably be using some of them in class next week.  If you know someone with photocopied ClassNotes from the Spring 2010 or Fall 2009 classes they should work fine this semester also. 

This class does not yet appear on d2l.  Though my Teaching Assistant and I are going to make an effort to do that this semester.

Next we looked at the Writing Requirements handout.  The first part of your writing grade is an experiment report.  You should be thinking about which of the 3 first experiments (or book or scientific paper reports) you would like to do so that you can sign up in class next Wednesday.  There aren't enough materials for everyone to do the same experiment.  Distribution of the materials for the Experiment #1 will probably begin in class next Wednesday.

So called One Side of One Page (1S1P) reports make up the second part of your writing grade.  Topics will appear periodically on the class webpage during the semester.  You will be allowed to write reports on up to 4 topics.  As you write reports you will earn points (the point total depends on the topic).  You can earn up to 45 points.  Bonus assignments will also appear during the semester (there is one available now as a matter of fact).  You can write as many bonus assignment reports as you want.  They won't allow you to earn more than 45 1S1P pts, but they will get you to the 45 pt. total more quickly.  Again please read through the Writing Requirements information and let me know if you have any questions.

Your grade in this class will depend on your quiz scores, how much extra credit you earn (from optional take home and in class assignments), your writing grade, and (perhaps) your score on the final exam.  A sample grade report from the Fall 2010 MWF Nats 101 class is shown below.


Don't worry about all the details at this point.  Note that this (fictitious) student earned a solid B in the class with Cs on the quizzes and the Final Exam.  The high writing grade and the extra credit points are what that possible.  Be sure you earn 45 1S1P pts (the maximum number allowed) and do the optional, extra credit, assignments.

Even though this was the first day of class we did cover some actual course material; partly just to give you an idea of how lectures will work during the semester. 

But first, something that I started last semester, a couple of Pictures of the Day.  Here's the first and the second.

If we were using a textbook it would probably begin with an introductory chapter that described the atmosphere.  What is the atmosphere made of, how do air temperature, air density, air pressure change with altitude?  That sort of thing.  That's what we'll do in this class (we'll also throw in a little material on air pollutants).  We'll spend a few weeks probably on material that would be in Chapter 1. 

Here are a few things to think about (not mentioned in class on Friday).

Can you see air?


You might think of air as being clear, transparent, and invisible (that would be true of the air in the classroom).  But sometimes the air looks foggy or hazy.  In these two cases you are seeing the effects of small water droplets (fog) or small particles of some sort (haze).  The particles themselves may be too small to be seen with the naked eye but are visible because they scatter (redirect) light.  Scattering is a pretty important concept and we will learn more about it in a week or two.  The sky itself is blue.  This is a little more complicated form of scattering of sunlight by air molecules.

Can you smell air?

I don't think you can smell or taste air unless air pollutants are present.  I suspect we can smell certain air pollutants even when the concentration is very small.

Can you feel air?


It is harder to answer this question.  We can certainly feel whether the air is hot or cold, but that have more to do with energy exchange between us and our surroundings.  And we are almost always in contact with air.  We will see that air pressure is pressing on every square inch of our bodies with 12 or 13 pounds of force.  If that were to change suddenly I'm pretty sure we'd feel it and it would probably really hurt.

What is air made of?  What specifically are the 5 most abundant gases in our atmosphere?
Let's start with the most abundant gas in the atmosphere.  I poured some of this same material (in liquid form) into a styrofoam cup.


It was clear, not blue as shown in the picture.  At least one student (probably many more) knew that this was nitrogen.  Nitrogen gas is invisible as are most of the other gases in the atmosphere.  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.  We'll use liquid nitrogen in several class demonstration this semester.

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 has a (very faint) blue color (I was pretty disappointed when I saw the picture the first time because I had imagined the liquid oxygen might be a deep vivid blue).

 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.  More about those in class next Wednesday.

Here are the 5 most abundant gases in the earth's atmosphere.


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 vapor is, in many locations, the 3rd most abundant gas in air.  In Tucson most of the year, 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.  We can see clouds even though the individual water droplets are too small to be seen because they scatter light.  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 gases are often used in "neon signs."

Here's a little more explanation (from Wikipedia) of why noble gases are so unreactive.  Don't worry about all these additional details.  The noble gases have full valence electron shells.  Valence electrons are the outermost electrons of an atom and are normally the only electrons that participate in chemical bonding.   Atoms with full valence electron shells are extremely stable and therefore do not tend to form chemical bonds and have little tendency to gain or lose electrons.

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.  The value of the dew point gives you an idea of how much water vapor is actually in the air.  The higher the dew point value, the more water vapor the higher the water vapor concentration.


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


Air temperature will always be equal to or warmer than the dew point temperature.  Experiencing 80o dew points would be very unpleasant (and possibly life threatening because your body might not be able to cool itself).  Click here to see current dew point temperatures across the U.S.  Don't worry about remembering all these numbers.  Just remember that the higher the dew point temperature the more water vapor is in the air and vice versa.  As you saw in class, I have trouble remembering these numbers.  If I can't remember them I can't really expect you to.

The second job of the dew point temperature is

We could use the cup of liquid nitrogen to show this.




The cloud came from moisture in the air.  The cloud was not made of nitrogen gas (which is invisible).  Note also that a certain amount of "artistic" license was used in the figure above; liquid nitrogen is not blue and water clouds are not green. 

This is where we finished up in class on Friday.  I may add a little bit more information over the weekend.  If I do, I'll review it quickly at the start of class next Wednesday.