Teacher Information:
I. Background:
To use the software NIH Image, students should be familiar with basic
Macintosh techniques, including opening a program, selecting an item be
clicking or double-clicking, selecting items in pull-down menus, and using
the mouse to maneuver the cursor across the screen.
II. Grade Level: Middle School or above
III. Important Concepts:
Plankton are tiny organisms that are carried by ocean currents.
Plankton include phytoplankton, which use chlorophyll to capture the energy
in sunlight.
The main types of phytoplankton are diatoms, dinoflagellates, and algae.
Phytoplankton form the base of ocean food chains.
The growth of phytoplankton is often limited by lack of CO2 or plant nutrients.
Gases such as CO2 dissolve more readily in cool water than in warm water.
Plant nutrients such as phosphates are continually washed into the seas
by runoff from the land.
An excess of plant nutrients, from sewage or farm fertilizers, is a type
of water pollution which can lead to undesirably-high levels of phytoplankton
in lakes, bays, and coastal areas.
High levels of phytoplankton can lead to the death of fish when both phytoplankton
and fish compete for oxygen during the night.
Red Tides are the result of population explosions of phytoplankton known
as dinoflagellates.
When shellfish feast on certain dinoflagellates, toxins harmful to fish
and humans become concentrated in their flesh.
If phytoplankton populations "crash" (a sudden "die-off"
due to changes in conditions), their decay consumes so much oxygen that
large numbers of fish may die due to lack of oxygen.
IV. Going Farther:
A. Obtaining Additional Ocean Color Data:
A free set of 5 CD-ROMs containing Sea Surface Temperature data and Pigment
Concentration data for 1978-1986 is available. To order it online on the
World Wide Web, go to the Web address http://podaac-www.jpl.nasa.gov/mail-orders.shtml
and select product #15, "AVHRR monthly global MCSST coregistered with
CZCS data". Complete the order form as specified. You should receive
your CDs in about a week.
The CDs incorporate data on daytime and nighttime sea surface temperatures
and on daily ocean color. All images except the "climatologies"
are monthly averages. (Climatologies for each month average the data over
all years.) Both full-resolution and reduced resolution ("browse")
images are included. Regional as well as global data sets are provided.
In addition images showing actual data only ("valid images")
are provided in addition to images in which missing data has been filled
in by interpolation ("interpolated images").
Converting Files from HDF Format to PICT Format:
To view the images with NIH Image , you must first open them with
NSCA Image , provided on the CDs in the "MAC" folder in
the "SOFTWARE" folder. Open NCSA Image , then pull down
the File menu and click Open . Select an image file to open
and click the button marked "HDF", then click Open . After
the image is displayed, select Save As and choose "PICT",
then save the image to a folder on your hard drive. The saved PICT image
can later be opened and manipulated using NIH Image .
The full resolution files are quite large. Unless you have ample RAM available,
work with the global "browse" images, in which each pixel represents
1 degree latitude and 1 degree longitude, or the regional images.
Suggestions for Student Activities:
The North Atlantic region includes the area of ocean into which the
Amazon and Orinoco Rivers of South America discharge their water. Locate
the mouths of these two rivers on the images and explore the impact of
the two rivers on phytoplankton abundance.
The Northeast Atlantic region includes data for the Mediterranean Sea.
Compare the phytoplankton abundance in the Mediterranean Sea to that in
the rest of the region. Are the results surprising?
Compare the images for daytime sea surface temperature and pigment concentration
for the same area during the same time period, noting similarities and
differences. Is phytoplankton abundance higher in cooler water or in warmer
water? Is the pattern consistent across the year? From the tropics to the
poles?
B. Obtaining Additional Data for the Chesapeake Bay:
Additional color data for Chesapeake Bay is available at the NOAA Chesapeake
Bay Office: Ocean Data Acqusition System web site at http://155.206.19.100/ODAS.html
. The data can be downloaded using Netscape as GIF files.
Converting GIF files to PICT files using GIFConverter:
GIFConverter is a shareware program you can download off the Internet.
Launch GIFConverter and open the image. Select Save As from
the File menu and then select "PICT". Click on Save.
The saved files can later be opend and manipulated with NIH Image
.
Suggestions for Student Activities:
During 1995, a drought reduced the flow of freshwater into the Bay.
Compare the cholorophyll data for 1995 to that for 1994.
Compare the cholorophyll data collected during the same time period
over several years, noting differences and similarities.
VI. How the Stacks Used in this Unit were Created:
A. The Annual Cycle Stack was created as follows:
The ocean color data used were obtained from the NASA Physical Oceanography
Distributed Active Archive Center at the Jet Propulsion Laboratory, California
Institute of Technology. (See above for information on ordering the free
CD-Roms.)
The 12 full-resolution climatology files in the Climate folder of
Volume 1 of the PODAAC CD-ROMs were opened with NCSA Image (provided
on the CD) and immediately saved as PICT files.
Each of the 12 PICT files was then opened with NIH Image and a rectangle
was selected, drawn from (1251,911), approximately (-140W, 70N), to (1707,
512), approximately (-60W, 0N). Each selection was saved as a TIFF file.
In each selected image, the black color of land masses was changed to white
using the paint-bucket tool. Then, using the eye-dropper tool and double-clicking
on 253 (used to mark coastlines), the color of the coastline outlines was
changed from grey to black.
A map showing U.S. Rivers was generated using the MapIt Web site
and downloaded. The image was then cut and pasted into the climate images,
stretching the image to match the distortion in the grid maps.
A label was created and pasted into the lower left hand corner of each
image. A color scale was created and pasted at the top of each image.
B. The Chesapeake Stack was created as follows:
GIF images for 1994 data for aircraft remote sensing of chlorophyll concentrations
were downloaded from the NOAA Chesapeake Bay Office: Ocean Data Acqusition
System web site at http://155.206.19.100/ODAS.html .
GIFConverter was used to convert all the GIF images to PICT format.
The shareware screen-capture utility Flash-It was used as indicated.
For each PICT image, the process was as follows:
Open image with NIH Image
Scale to fit window
Select, begining at (45,660) and moving (445X660)
Copy selection
Save selection as "cut" (This removed excess borders.)
Open cut image
Scale to fit window
Take screenshot of window using Flash-It
Save as "snap" (This produced a screen-size image, but as large
as possible.)
Open "snap"
Select map portion of image (about 170X338)
Copy selection
Paste into Master image, created by manipulating first snap image
Add title, beginning at (75,404)
Save as ... (This created uniform final images.)
activity created by Mary V. Ball, ballm@cncc.cn.edu and adapted
by NSF Network Montana Project, Dec. 1996.