4. Seasonal changes
a.) Open the movie called nw_africa_movie (not available here
yet) to view an animation that displays a sequence of monthly composite
images for an area in northwest Africa upwelling area for the period 1979
to 1985. This composite was created from 2181 individual scenes collected
by the Coastal Zone Color Scanner (CZCS) on board the NIMBUS-7 satellite.
Colors are pigment concentrations, with red colors indicating highest values.
Note the variation in upwelling from month to month.
On which part of the coastline is the upwelling current strongest? Label
the strongest upwelling zone on a paper map of northwest Africa.
b.) The images below show sea-surface temperatures (SSTs) for northwest
Africa for two months during 1982. Summer conditions are on the left and
winter conditions are on the right. The colorbar at the base of the images
shows the temperature scale in degrees Celsius.
Upwelling often has a seasonal component, as wind directions may change
from one season to the next. Along the California coast, upwelling is strongest
in the summer, when winds from the north are prevalent.
Based on the satellite images, would you say that upwelling currents
are strongest in the winter or in the summer along the coast of northwest
Africa? Speculate about a possible cause of this seasonal variation.