This
lesson uses a data set that is a collection of monthly means (averages)
of sea surface temperatures (SST) during the years 1981 through (as of
this writing) 1997. The data were derived from a combination of measurements
from satellite-borne instrumentation and on-site ship and buoy platforms.
These blended SST data provide a means of monitoring both the long- and
short-term variability of the dynamic and thermodynamic properties of the
ocean on a global scale.
Exploration
1. Take a close look at a current sea surface temperature map shown above. Write a brief description that describes each of the Earth's oceans.
2. What do each of the colors on the map represent? What is the water temperature near Hawaii, near the Falkland Islands, near Madagascar and near Jamaica?
3. If time allows, watch a movie of changing sea surface temperatures. How does the temperature change over time?
Concept Introduction
To make an analysis of global sea surface temperatures, we will use data from the Goddard DAAC Interdisciplinary Data Collection Homepage.
PART A: Locating and downloading the image of Sea Surface Temperature data.
2. This takes you to a page titled Sea Surface Temperature from NOAA NCEP. On this page, click NCEP Sea Surface Temperature this leads to an ftp site. Scroll down to find and click on the file folder labeled: gif. These are images of Sea Surface Temperatures from November 1981 through 1997. As described above they are monthly averages of combined satellite and earth born measurements.
3. Click on a few to get a feel for what the data looks like.
5. Quit Netscape.
6. Open Graphic Converter (or Paint Shop Pro, or other similar software). Choose OPEN from the FILE menu. Navigate to the file you saved from the Internet and open it.
7. Choose SAVE AS from the FILE menu. Select PICT (or TIFF) as the format. Create a new folder called 'PICT (or TIFF) images.' Click SAVE.
8. Quit Graphic Converter.
9. Open NIH Image (download mac or pc as needed). Choose OPEN from the file menu. Open the new pict (or tiff) image you just created.
11. What color is the ocean where it is cold?
12. What is the range of pixel values? (lowest to highest)
13. Choose Show Histogram from the Analyze menu. Move the cursor over the value that has the most pixels. What value is that?
14. Find that value on the sea surface temperature picture you downloaded. What color is it? (You could also look in the LUT.)
Changing Sea Surface Temperatures for a year
PART A: Now that you have done it with one image, try it with one image each month for a year. This will show how the temperatures change during the year.
16. Open the Sea Surface Temperature file for 1986. What you see is monthly averages for 1986.
17. Download the 1986 folder. To download the image, select the image and hold down the mouse button (right mouse button on the PC). A pop-up menu will allow you to SAVE THIS IMAGE.
18. Use Paint Shop Pro or GIF Converter (or other image tool) to save each monthly image individually by cutting and pasting. (NOTE: All images must be the same size in order to animate them.) Label the images in a easy to remember way: for example, Jan86 or 8601 for January, Feb86 or 8602 for February, etc.
19. Use Graphic Converter (or one of the above image tools) to convert all 12 images to PICT (or TIFF) and save in a new folder called SST monthly.PICT (or SSTmonthly.TIFF)
21. Open your image processing software (ex. NIH Image). Choose Open from the File menu.
22. Locate your new image folder and open it.
23. Click on OPEN ALL in the Open dialogue box. Click OPEN.
24. Choose Windows to Stack from the Stacks menu.
25. Choose Animate from the Stacks menu. Control the speed with the number keys.
27. What is the highest pixel value? What is the lowest?
28. Watch the southern hemisphere and record similar observations.
Repeat CONCEPT APPLICATION section but choose the same month from the GIF images folder for each year. You may not want to do every year, but choose 8-10 images to create a movie.
Actually any data can be imported into NIH Image and displayed. If students want to take other data, put it into a tabular form and import it into NIH Image, they will see how much data is in the SST images they have been examining. Instructions for this are in the NIH Image manual available from the National Institute for Health (NIH) website.
The esthetics of the SST images are evident from the first image you work with. You can manipulate thesee images and the various Process filters to produce interesting artistic displays. You can collect current images from the internet and animate them.
Acknowledgements
The production and distribution of this data set are being funded by NASA's Mission To Planet Earth program. The data are not copyrighted; however, we request that when you publish data or results using these data please acknowledge as follows:
The authors wish to thank the Distributed Active Archive Center (Code 902 .2) at Goddard Space Flight Center, Greenbelt, MD, 20771, for producing the data in its present format and distributing them. The original data products were produced by the NOAA/NESDIS/NCDC Climate Analysis Center, Asheville, NC. Goddard's share in these activities was sponsored by NASA's Mission to Planet Earth program
