Part 1—Investigate Sea Surface Temperature (SST) in the Pacific Ocean

Step 1 – Set up a Base Map

1.  Start My World GIS by double-clicking its program icon or by going to the Start Menu (PC) and navigating to the application.

2.  From the Welcome screen, click the link titled "Get Started" at the bottom of the screen.

3.  Switch to the World data library. Then drag the Lines of Latitude & Longitude and the Continents layers to the layer list.

4.  Click the Visualize tab below the menu items to switch from Construct Mode to Visualize mode. To find the modes, look at the tabs along the top of the map. Their names will show as your cursor hovers over them.

5.  Once in Visualize, click the Zoom to All button to re-size the map to fill the window.

Step 2 – Import Sea Surface Temperature (SST) data from the Pacific Marine Environmental Laboratory (PMEL)

1.  Download datasets from the Pacific Marine Environmental Laboratories (PMEL). To do this go to File> Open> T:> Teachers > Guzman > Handout > PMEL_case_study.m3vz.

2.  Once you have opened the file, save to your H drive and the new data should begin to load.

3.  Click the Zoom to All button to re-center the entire map. You should now have a map view that contains three layers.

o  Lines of Latitude & Longitude

o  Continents

o  Weekly Means of SST (may be colored either gray or blue)

Step 3 – Investigate Sea Surface Temperature (SST) in the Pacific Ocean

1.  Begin your exploration of the weekly SST data by double checking to make sure the color scheme for the SST for the week of December 7, 1982 is colored correctly. 1982 is the first option listed.

2.  This layer represents the weekly SST data for December 07, 1982. The legend along the bottom of the map will help you to interpret what the colors of the map are showing. Just by looking at the colors of the map and the legend, what is the approximate sea surface temperature along the equator?

3.  Just by looking again, what is the approximate SST surrounding the continent of Antarctica?

4.  Select the pointer tool and place your cursor in the Pacific Ocean on your map. Click your mouse button at several locations and read the information My World reports for each click. This will allow you to select specific locations and read the SST data at that location.

5.  Hold your mouse button down as you move the pointer tool north or south on the map. How do the temps change as you move away from the equator toward either pole?

6.  Move the pointer tool east or west. How do the temperatures change as you move along a single line of latitude?

7.  Change to the SST grid for the week of December 14, 1982.

Notice that the color scheme changed but the range of temperatures is still about the same. My World doesn't know what kind of data these are, so it assigns color tables randomly. It does not indicate a drastic change in temperature in this short time.

Step 4 – Edit Appearance of the SST Layer

1.  In order to have the map look more typical you will need to edit the layer 's appearance. First double-click to select the layer.

2.  Next, change the temperature range minimum to -2 and the maximum to 32. Then copy your new color scheme to all the SST grids.

Step 5 – Investigate SST in a "Normal" Year

In order to establish the "normal" SST pattern for all Decembers, create a new field that is the average (mean) of all the weekly averages from 1982 through 1998. Enter Overall Average SST for December, 1982-98 as the name for the result.

1.  Click the Analyze tab.

2.  Under Add Field(s) to Layer, choose By Math Operation.

3.  In the 'Add Field to the Table of' dialog box, use the drop-down menus to Add a Field to Weekly Means of SST by computing a Mean (average).

4.  Click the radio button to compute the value from more than two fields, and check all the grids that represent weekly SSTs from 1982 through 1998. Alternately, click the Select All button, then deselect the non-SST layers at the bottom of the checklist.

5.  Enter Overall Average SST for December, 1982-98 as the name for the result. We'll refer to this field as the Overall Average.

6.  Select OK which will perform the calculation and return you to Visualize mode. The "Overall Average..." will be displayed.

7.  Change the color scheme by double clicking on the “Weekly Means of SST” layer and choosing “Temperature” for the color scheme. You map should appear similar to the one below.

8.  Looking at the map you’ve just created, describe exactly what makes this a “normal” year, focusing on the sea surface temperature off the coast of Peru. You may zoom in to get a closer look if needed.