ozone layer

Part 2. Mapping the Ozone LayerWe will now use satellite images to examinethe actual size and thickness of the hole in the ozone layer. We will use realTotal Ozone Mapping Spectrometer (TOMS) data from the EarthProbesatellite. These images show how much ozone was in the atmosphere over the Southern Hemisphere from 1996 to 2005, when TOMS was disabled. (The newer data requires much more sophisticated software). We will interpret the images to identify and quantify theozone “hole” that develops in the atmosphere near the South Pole every year during the Southern Hemisphere’s spring.1.Now you are going to analyze the ozone layer from October 1 on 10 consecutive years, from 19962005. These satellite shots have already been downloaded for you fromNASA’s website.a.In the course’s Canvas Files folder, locate the folder called Lab Info.b.Inside that folder is a zipped folder called, Lab01_ozone_tiffs.z.zip. Thisis a zipped folder with 10 image files.c.Save the zipped folder in a new folder named “TOMS Images” on your computer. d.Double click the folder to extract the 10 images.Move them out of the zipped folder into your newly created folder. Do not skip this step.2.You will need some imaging analysis software to examine the NASA images.a.Go to the Image J website for a free download: https://imagej.nih.gov/ij/download.htmlb.Choose the proper software according to your computer system.i.Note that this program works much betteron a Windows computer, so if possible use a PC for this lab.c.Save the zipped file on your computer. For Windows, it is recommended that you create a newImageJfolderin the Documents folderand install it there, rather than in the Program Files directory.d.Double click on the zipped folder, then on the ImageJ folder, then on the ImageJ application icon. It will ask if you want to extract all the files. Click “Extract all.”i.Or a downloaded or zippedfolder will open, then copy the entire ImageJ folder to your Documents folder. ii.You MUST copy the files from the zippedand Downloadsfolder to a new folder for the programto work.3.OpenthecopiedImageJ folder. Double click on the ImageJ microscope icon to launch the application.It is the last thing in the list below.

4.When ImageJ opens, you will only see a small rectangular menu bar. On an Apple computer, it is long and thin and easy to miss. Here is how it looks when it opens with a Windowsbased computer:5.Now we want to import our ozone hole TIFF images as a stack.This means the program willlook at these 10 images as a sequenced group.6.The easiest way to do this is to drag and drop the Ozone TIFFS folder on the menu bar.a.Gto the folder that contains the saved Ozone TIFFS folder and drag the entire Ozone TIFFS folder onto the bottom of the ImageJ menu window. b.Click the option to Use as Virtual Stack.c.If you did it right, the first satellite image will open automatically.d.Resize it so you can see the sliderat the bottom of the image.Use this to scroll through the 10 images. You can also usethe arrow keys or even the comma and period on your keyboard.7.Before working with the images, save the stack as a TIFF file by going to File > Save As >Tiff, then choose a folder and name for the saved stack, such as My Ozone Stack.8.These images show the amount of ozone in the upper atmosphere in Dobson Units (DU). a.If all of the ozone molecules were put into an actual “layer” of ozone, it would be about 3 millimeters thick or 300 DU.

b.Technically, the ozone “hole” is defined as the area where the amount of ozone is < 220 DU. Because of this color scale, we will use the threshold of 225 DU for the ozone hole.c.Look at the color scale below the first image to figure out where ozone is “thickest” and “thinnest.” Can you identify the area that would be considered as part of the ozone hole?d.Look through the stack of images and note how the ozone levels and the size of the lowozone area change over time. Write down your observationsfor several of the years’ mapsin your lab notebook.To zoom in on the image, select the magnifying glass on the tool bar, then click any location on the image.To zoom out, doubleclick the magnifying glass on the tool bar.To scroll around the image while it is enlarged, select the hand on the tool bar, then click and drag on the image.To read the x,y location or the value of the pixel under your cursor, look just below the tools in thestatus bar.To animate the stack of images, choose Image > Stacks > Tools > Start Animation. Choose Image > Stacks > Tools> Animation Options… to control the animation speed.9.We can use ImageJ to measure quantitatively changes the hole by counting the number of pixels that are part of the hole each year. You will do this by highlighting the area of the hole for each year so the program can count the pixels in the selected area. You will need to close the stack (don’t save any changes) and reopen it. a.Within ImageJ, choose File > Open > your stack name.10.Now let’s quantify the extent of the ozone hole. First, remove the continent outlines that can interfere with the highlighting. Select Process > Noise > Despeckle. When queried to process all the slices, select Yes.11.To start the highlighting, we will use thresholding to specify a range of pixel values (the ones that represent the ozone hole, for instance) and highlight them in the image. Select Image > Adjust > Threshold. In the Threshold dialog box, below the two horizontal sliders, verify that the drop down menu on the right is set to “Red.”12.Now drag the top and bottom sliders or click on the arrow buttons until the pixels that are the colors representing ozone measurements <225 are red and pixels of higherozone levels remain unchanged. Close the threshold window by clicking the x in the corner.13.From the ImageJ toolbar, select the wand (tracing) tool (a very small magnifying glass) and click it just to the left of the area of red that represents the ozone hole on the image. a.A yellow selection line will appear around the red pixels. b.If the yellow selection is off, just reclick the wand tool outside the red areas again. It may take several tries to get the line to draw.14.Now let’s quantify the ozone hole. Select Analyze > Measure.a.The area (in pixels) you selected and measured is displayed in the Results window. b.To bring the Results window forward, select Windows > Results.15.Use the slider button along the bottom of the stack window to advance to the next image.

16.On the next image, click the wand tool to the left of the ozone hole again to trace the new outline.17.Choose Analyze > Measure to record the measurement in the Resultswindow.18.Repeat these stepsuntil you have measured the area of the ozone hole for all 10 years.a.NOTE: If you record an incorrect measurement in the Results window, try selecting it in the Results window then choose Edit > Delete. b.If you cannot delete single measurements, you can choose Analyze > Clear Results to start over, or you can delete bad measurements once you bring the results into your spreadsheet application.19.Save the Results file by choosing Window > Results, then choose File > Save As. Save itwith the default name of Results.xls. Store the Results file in the same place as your TOMS images.20.Now open the results in Excel (or a similar spreadsheet program). These steps refer to Excel.a.Choose File > Open and find your Results file, click Open.b.Ifthe Text Import Wizard opens, select the default selections, by clicking Next >, Next >, and Finish to open the file.c.Change the header of column A to Year, and change the 110 values in column A to years, listing one year for each row, from 19962005. 21.Graph the results by selecting the years and ozone hole area measurements in columns A and B.Be sure that years are on the x axis.a.Choose Insert > Chart. Choose the Area chart type.b.Use the Chart Options menu to enter a title for your graph plus appropriate names for each axis. You may also want to customize other options such as colors, grid lines or data labels.c.The data in the columns and the graph must be together on one page22.When you are pleased with your graphdisplay, save your worksheet.23.Answer the three Discussion Questions below in the worksheet, too.24.Submitthe worksheet with the graph and questions along with your notes from the weather exercise in Part 1.Discussion Questions for Lab 11.Analyze the results in your ozone hole graph. Did the size of the ozone hole increase, decrease, or stay the same over the nine years you analyzed? What do you think might account for the various changes?2.Why was the ozone hole for one year much smaller than the others? Do some research and explainin your own words. Include the properly cited source.3.What has been the trend in the size of the hole in the ozone layer since 2005? Do some research and explain in your own words. Include the properly cited source.

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