ERTH 535:
Planetary Climate Change
(Spring 2018)
Lab Activity #11:
Land/Water Contrasts

(For class Friday, April 13)
Dr. Dave Dempsey
Dept. of Earth & Climate Sci.,

(For on-line access to this activity, go to


Instructions and Questions

  1. 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?

  2. 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,
    Area-weighted, 30-Year Mean Temperatures (°F)
    N. Hemisphere Midlatitudes
    , 1930-1960
    Dec 1986 263.8 285.6 Dec 14.8 54.5
    Jan 1987 262.1 283.7 Jan 10.9 51.2
    Feb 1987 265.7 282.8 Feb 12.7 50.05
    Mar 1987 269.2 282.9 Mar 26.9 50.11
    Jun 1987 290.3 287.0 Jun 64.0 57.2
    Jul 1987 293.1 289.5 Jul 68.4 62.5
    Aug 1987 291.7 291.3 Aug 66.1 66.3
    Sep 1987 286.1 290.0 Sep 55.2 65.7

    1. 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?)

    2. 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?

    3. What about the minimum and maximum mean monthly temperatures over midlatitude oceans? Do they occur at the same times as they do over land?

  3. 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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