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- Observe day-to-night and seasonal differences between land and ocean responses
to radiative heating and cooling, using a different source of data for each.
- Try to account for the observed differences between land and water.
Instructions and Questions
- Day/night ("diurnal") temperature variations. In Lab
Activity #8, you saw an infrared
satellite loop for most of the earth lasting several days. Based on your
understanding of how to interpret these images, what can you conclude about
the variation in temperature between day and night of the land surface compared
to the ocean surface? How can you tell?
- Magnitude and timing of seasonal temperature variations. Using My World GIS, we can calculate
the area-weighted, monthly mean temperature in the Northern Hemisphere over (a) midlatitude land areas,
and (b) midlatitude ocean areas, for each of the months from December 1986 to March 1987 and from June to September 1987. We can do the same for the 30-year average from 1930-1960. The results are:
Area-weighted Monthly-Mean Temperatures (K)
N. Hemisphere Midlatitudes, 1986-87
Area-weighted, 30-Year Mean Temperatures (°F)
N. Hemisphere Midlatitudes, 1930-1960
- What can you conclude about the seasonal variation in temperature over land
areas vs. over ocean areas at midlatitudes? (Would you expect to see the same effect at
low latitudes, or at least in the tropics? Why or why not?)
- When does the monthly mean temperature over midlatitude land areas reach a minimum? Does this occur when the sun is least intense? (Why or why not?) What about the maximum monthly mean temperature over land?
- What about the minimum and maximum mean monthly temperatures over midlatitude oceans? Do they occur at the same times as they do over land?
- What differences between the physical properties of land (rock/sand/soil) and water
might account for your observed differences between land and ocean areas in (1) and (2) above?
(Hint: there are four physical properties that are different for land and water and that help explain why ocean surfaces warm less
during the day and in summer than land surfaces do. Two of these properties also help explain
why ocean surfaces cool less at night and in winter than land surfaces
do, while the other two can't.)
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