ERTH 535:
Planetary Climate Change
(Spring 2018)
Supplement to
Lab Activity #4
Dr. Dave Dempsey
Dept. of Earth & Climate Sci.
SFSU

Introduction to Earth's Energy Budget:
My World GIS Instructions

For Part 1: A Simple Model of Absorbed Solar Energy at Earth's Surface

          Item (3) of Lab Activity #4 asks you to test your simple, conceptual budget (model) for solar radiation absorbed by the Earth (item (2) of Lab Activity #4), using actual satellite observations analyzed and plotted using My World GIS. To access the plots that you need, do the following:

  1. Start My World GIS and fill the screen with its window.
  2. Pull down the "File" menu, select "Open Project..."
  3. In the resulting "Open Project" dialog window, click on the "Home" icon and navigate to Courses > E535 > Class.
  4. Select the file "PlanetaryRadiationBudget.m3vz", then click on the "Open" button.
  5. In the left-hand sub-window ("Layer List"), highlight (click on) the "MonAvg_RadiativeBudgetTerms.wwf" panel.
  6. In that panel, pull down the menu and select "Absorbed Solar 03-1987-Mar.wwf".
  7. On the main menu bar (upper left edge of My World GIS), pull down the "Windows" menu and select "New Child Window...". (This opens the Absorbed Solar plot for March 1987 in a new window.)
  8. Back in the "MonAvg_RadiativeBudgetTerms.wwf" panel, pull down the menu and select the field representing the right-hand side of the equation in Item (2) of Lab Activity #4 that you hypothesized. (You should find it among the last 20 or so fields on the list.)
  9. Verify that the color tables and the color scales for the two plots now on your screen are the same, so you can compare them visually.
  10. On the toolbar just above the plot in either window, click on the "arrow" icon, then click anywhere on either plot to sample the radiative flux value at that spot on both plots. (The values at the same location on both plots, expressed in Watts per square meter, should appear along the color scale below each plot.) You can then drag the cursor around to other parts of the plot(s) and compare values at other places.

Part 3: Space-Bound Longwave Infrared Radiation

          Item (10) of Lab Activity #4 asks you to look up the global mean area-weighted, monthly average spacebound energy for January, March, and July, 1987. To do this:

  1. If you haven't done so already, follow the first four steps for Part 1, Item (3) above.
  2. In the left-hand sub-window ("Layer List"), make sure that both the "MonAvg_RadiativeBudgetTerms.wwf" and "MonAvg_IncomingSolar.wwf" panels are closed. (To close a panel, click on the "eye" icon in the upper-right corner of the panel. The "eye" icon should then be replaced by a blank square.)
  3. Open the "MonAvg_OutgoingEnergy.wwf" panel by clicking on the blank square in panel's upper-right corner. Click on (highlight) the panel. You should now see a plot of area-weighted, monthly-average "spacebound" energy (that is, flux of longwave infrared radiation emitted by the earth to space) for January, 1987. If you pull down the menu in the "MonAvg_OutgoingEnergy.wwf" panel, you'll see two more such plots, for March and July of 1987, on the list.
  4. In the row of icons across the top of the "Layer List" sub-window, click on the "Show Statistics for Active Layer" icon (which looks like the capital Greek letter sigma, which is commonly used in mathematics to represent summation).
  5. In the resulting table of statistics about monthly average spacebound energy, locate the row that represents the global mean value ("Mean") and the columns for area-weighted spacebound energy for January, March, and July of 1987, respectively (near the far right-hand end of the table).

Item (10) of Lab Activity #4 also asks you to look up the global mean area-weighted, monthly average incoming solar radiation, reflected solar radiation, and/or absorbed solar radiation for January, March, and July, 1987. To do this:

  1. If you haven't done so already, follow the first four steps for Part 1, Item (3) above.
  2. In the left-hand sub-window ("Layer List"), make sure that the "MonAvg_RadiativeBudgetTerms.wwf" panel is open. (To open a panel, click on the blank square box in the upper-right corner of the panel where the "eye" icon appears when the panel is open.)
  3. Click on (highlight) the "MonAvg_RadiativeBudgetTerms.wwf" panel.
  4. In the row of icons across the top of the "Layer List" sub-window, click on the "Show Statistics for Active Layer" icon (which looks like the capital Greek letter sigma, which is commonly used in mathematics to represent summation).
  5. In the resulting table of statistics about monthly average spacebound energy, locate the row that represents the global mean value ("Mean") and the columns for area-weighted absorbed solar, incoming solar, and/or reflected solar for January, March, and July of 1987, respectively (near the far right-hand end of the table).

For Part 4: Variations with Latitude of Outgoing Longwave IR Radiation and Absorbed Solar Radiation

          Item (12) of Lab Activity #4 asks you to examine north-south profile plots of monthly average space-bound energy (outgoing longwave radiation) data sets for January, March, and July, that have been zonally averaged (that is, averaged spatially along each east-west band of cells circling the globe, where each such band is 2.5° latitude across from north to south). Zonal averaging removes east-west variability from the plots and allows you to focus on (average) north-south variability.


For Part 5: Outgoing Longwave IR Radiation from Top of the Earth's Atmosphere vs. from the Earth's Surface

          Item (15) asks you to look up the area-weighted global average of the annual-average outgoing longwave IR radiation ("spacebound energy") fluxes for 1987.

  1. Click on (highlight) the "Zonal Average Outgoing LW Radiation" panel in the "Layer List" sub-window. (It doesn't matter whether or not the panel is open.) (Note: "Outgoing LW Radiation" and "Spacebound Energy" are the same thing.)

  2. Make sure that the "Visualize" tab is selected.

  3. Click on the "Show Statistics for Active Layer" icon (the "Σ" icon) on the tool bar above the panels in the "Layer List" sub-window. In the resulting summation statistics window, scroll to the right until you locate the column containing statistics for the field of area-weighted, annual- and global-averaged spacebound energy for 1987. Among those statistics, the (global) mean is what we want.

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