### Meteorology: Understanding the Atmosphere            Ackerman and Knox

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Follow these general rules of contouring as you contour maps:

1. isopleths should never cross,
2. isopleths should not branch or fork,
3. only the area on the map that has data should be contoured,
4. you should label your isopleths (in these exercises we will color code them).

When you finish contouring check your results. One way to do this, is to imagine that you are walking along an isopleth. The values of the data points one side of the line should all be greater than, or all of them should be less than the value of the isopleth.

Lesson 1: Introduction to contouring
In this first exercise, you will use the mouse to practice contouring. You might start analyzing a contour by drawing tic marks on the map to mark where the isopleth should be, then connect the dots. Don't worry about trying to get the lines perfectly smooth. The purpose is for you to gain an understanding of how contouring is accomplished. Notice that contour lines cannot cross, but they can form closed loops.

Lesson 2: Learning the Basics
In this next exercise, you will again use the mouse to contour a map. You will be presented with a series of plotted data points that will determine the contoured field. Contour the field before looking at the answer! As you go through this first exercise notice how the contour field changes as you add observations to the map. The more observations you have, the better the field is defined.

Lesson 3: Intermediate Level
To become adapt at contouring requires practice!
When you are done with this map, notice the spacing of the contours. The spacing of the isopleths indicates how rapidly conditions are changing in the horizontal direction. The gradient of a variable describes how much the variable changes over a given distance. The more densely packed the isopleths, the larger the gradient.

Lesson 4: Working with Real Data
In this exercise you will be presented with observations of surface dew point temperatures on 1200 UTC, July 18, 1996. Unlike the previous exercises, all the observations are plotted on the map at once. But don't let this bother you. Before drawing your first contour invest some time in preparation.

 First look over the numbers and search for continuity. Are there regions where the numbers are changing rapidly (large gradients)? Are there regions of the map where there is little variation in the numbers (referred to as a flat field)? What is the largest and smallest number? Starting with two observations begin drawing your first contour. Then mentally add in surrounding pairs of observations as you continue to draw the contour. If you make a mistake you can hit the "Erase Last Line" button, or just ignore the line.

In real analysis lab, you would be using a pencil instead of a computer mouse so that you can erase the inevitable mistakes.

Lesson 5: Working with Weather Maps
In this exercise you will be presented with a weather map that includes observations of temperature, dew point temperature, and wind speed and direction made at 1400UTC on July 18, 1996. On this day a tornado touched in in Oakfield, WI. The observations are all plotted on the map at once, so don't get temperature confused with the dew point! Do you notice a relationship between temperature and dew point?

Lesson 6: Working with Ocean Maps

Oceanography is another science that uses contouring to analyze data.  In this exercise you will be presented with salinity data measured in the Mediterranean Sea.  When compared to weather observations taken over land, there are very few observations made in the oceans.  No matter what the data source, the approach to contouring is the same.