Skip to content. | Skip to navigation

Personal tools

Benguela Upwelling


Benguela_chapter_title_graphicBenguela upwelling zone, chlorophyll concentration title graphic


Questions to Explore

  • What is the extent of the Benguela upwelling?
  • How are sea surface temperature and chlorophyll concentration in this region related?   What causes this relationship?


Data Frames for this Chapter

Sea Surface Temperature (MODIS)

Chlorophyll (MODIS)


Visualizations for this Chapter

Animation (Giovanni)

Scatter Plot (Giovanni)

Line Fit (Giovanni)

Scatter Plot (NEO)

Transect (NEO)


Location and Map Coordinates

Location map for Benguela Upwelling Zone, western coast of southern Africa

Latitude longitude coordinate box

Just off the western coast of South Africa lies the Benguela upwelling system.  Upwelling occurs when cold water from beneath the surface rises to the surface, bringing nutrients from the deep ocean.  Phytoplankton benefit from the increase in nutrients and grow rapidly as a result.  Therefore, both chlorophyll and sea surface temperatures are appropriate parameters to measure the scope of the upwelling. 


Animation (Giovanni)

1. Select the area specified above.

2. Parameter: Chlorophyll a (MODIS)

3. Temporal:      Begin Date = 2005, Jan

                            End Date = 2007, Dec

4. Select Visualization: Animation

5. Generate Plot

Benguela upwelling zone MODIS chlorophyll concentration image for April 2006 (animation sequence excerpt)

1. Select the area specified above.

2. Parameter: Sea Surface Temperature (MODIS)

3. Temporal:      Begin Date = 2005, Jan

                            End Date = 2007, Dec

4. Select Visualization: Animation

5. Generate Plot

Benguela upwelling zone MODIS sea surface temperature image, April 2006 (animation sequence excerpt)

Although this shows the large-scale upwelling, we can zoom in to see more accurate changes in chlorophyll and sea surface temperature.

Scroll down the Giovanni output page to set more specific parameters.

Coordinate System:

To see the change on a much smaller scale, zoom into the following coordinates:

Latitude longitude coordinate box

Custom Color Scale:

For the sea surface temperature plot -

Under Edit Preferences, change the Color Scale to Custom.

Choose the Custom scale:         Min: 4

                                                   Max: 19

Color Palette:

You can also try out different color palettes to see how they display the data:  for example, change to the “Ocean” color palette.  The result of these steps is shown below.

Benguela upwelling zone MODIS sea surface temperature image, with custom temperature scale and custom color palette


Scatter Plot (Giovanni)

  1. Select the area specified above.
  2. Parameters:            Sea Surface Temperature (MODIS)

                                    Chlorophyll a Concentration (MODIS)

  3. Temporal:    Begin Date = 2002, Jan

                        End Date = 2007, Dec

  4. Select Visualization: Scatter Plot, Time-Averaged
  5. Generate Plot

Chlorophyll versus temperature scatter plot, July 2002 to December 2007, for Benguela Upwelling zone


Line Fit (Giovanni)

  1. Create a scatter plot for a small area of the Benguela upwelling using these  latitude-longitude coordinates:Latitude longitude coordinate box
  2. Under Edit Preferences, choose Yes for Line Fitting
  3. Record the equations and the r-value. 

Benguela Upwelling Zone chlorophyll versus temperature scatter plot for small coastal area, showing linear relationship between SST and chlorophyll


Scatter Plot (NEO)

  1. Use the following coordinates:Latitude longitude coordinate box
  2. Select the following data sets:
    Sea Surface Temperature (MODIS) for August 2006

                                Chlorophyll a Concentration (MODIS) for August 2006   

  3. Under Area, enter the coordinates used for the Giovanni example.
  4. Click on ‘Zoom and Roam.’  Use the right click to zoom in and the left click to zoom out.  By holding and moving the mouse, you can roam the image.  Use this until you are sufficiently zoomed into the image.
  5. Click Outline Region.  Using an irregular shape, outline the closest region to the shore.
  6. Click Scatter Plot.Benguela Upwelling Zone, NEO chlorophyll image, chlorophyll versus SST scatter plot, near coastal region
  7. Make various scatter plots farther from the coastline. 


Benguela Upwelling Zone, chlorophyll image, chlorophyll versus SST scatter plot, offshore region


As in the Giovanni example, change the area to these zoomed coordinates:

Again, outline the area and create scatter plots.

Benguela Upwelling Zone, chlorophyll image, SST versus chlorophyll scatter plot, northern region


Transect Plot (NEO)

  1. Under Area, enter the zoomed coordinates above.
  2. Click on ‘Zoom and Roam’ and then click Probe.
  3. Click ‘Plot Transect’ 
  4. Chose region to draw the transect.  Make sure to record the coordinates of this line.

Benguela upwelling zone, SST image, SST and chlorophyll transect plot, with lower SST and higher chlorophyll close to coast

Although hard to see, the temperature actually drops off 3°C (from 15°C to 12°C.)  Look closely near the red arrow to see the decrease in temperature which occurs right at the coast, where the upwelling occurs.  



  • Using the Outline Region function, map the boundary of the upwelling according to the sea surface temperature and the chlorophyll.  What is the area of the upwelling?  What are the approximate coordinates?
  • What does the scatter plot tell us about the relationship between temperature and chlorophyll?  Why does this relationship occur?  How strong is the relationship?
  • The r-value is the correlation coefficient.  In other words, it shows how well the points fit a line.  R ranges from -1 to 1.  1 signifies a perfect direct correlation.; -1 signifies a perfect inverse correlation; and 0 signifies no correlation. What is the r-value for both Giovanni scatter plots?  Which data has a better fit and why?
  • The relationship or slope between chlorophyll concentration and sea surface temperature varies based on the scale of the plot in NEO.  Why does the scale change over smaller areas?  
Document Actions
NASA Logo -
NASA Privacy Policy and Important Notices
Last updated: Apr 08, 2014 09:51 AM ET