Introduction to Clouds

Analyzing the Distribution of Cloud Types in a Midlatitude Storm

What Kinds of Clouds Are Produced by Midlatitude Storms?

You will now use the same satellite data to determine the true percentages of all cloud types occuring in a storm. By analyzing the data using a spreadsheet program you can see the distribution of the cloud types. The steps listed below will guide you through a short analysis of this midlatitude storm data. The automated part of the procedure requires Microsoft Excel, and is optimized for Windows and MacOS. If you are using a UNIX system, analyze the data with any spreadsheet/data analysis program available on your system.

Determining the True Percentages of Cloud Types in a Storm

1. Select the region of your storm with the most clouds: Click at the point just below the black pixel on the left side of the Optical Thickness image. Holding down the mouse button drag the cursor to select a region that is 10 pixels wide by 10 pixels high. Notice a similar box appearing simultaneously on the second image. When you release the mouse button, the numerical data for each property for the region you have selected will appear.
   
   
2. Open the "Storm Analysis" worksheet for your version of Microsoft Excel: In this introduction much of the process has been automated. Download and open the appropriate worksheet for your version of MS Excel. Ensure that you "Enable Macros" if prompted with a choice on opening the spreadsheet in MS Excel:
   
   • Windows - Microsoft Excel 97 and newer
   • Macintosh - Microsoft Excel 5 and newer
   
   
3. Copy the Optical Thickness data into the first column of the spreadsheet: You should now have MS Excel running in conjunction with your Web browser. On the data display above, click the mouse button at the top in Optical Thickness data column and select and copy all the data [ Windows users: Right-click and choose "Select all" from the pop-up menu; right-click again on the selected data and choose "Copy". Mac users: click and press Command-A and then Command-C]. Go to Microsoft Excel, and paste the data into the first column right below the title "Cloud Optical Thickness" [ Windows users: right-click in cell A2 and choose "Paste". Mac users: click in cell A2 and press Command-V]. The data should appear in the Excel column.
   
   
4. Copy the Cloud Top Pressure data into the second column of the spreadsheet: Following the same procedure, copy the Cloud Top Pressure values from the second data column into the second column in Excel just below the title "Cloud Top Pressure (mb)" [ Windows users: right-click on the second data column above, choose "Select all"; right-click again and choose "Copy"; right-click in cell B2 in Excel and choose "Paste". Mac users: click on the second data column, press Command-A and then Command-C; click in cell B2 in Excel and press Command-V].
   
   
5. Produce a graph of the data using Excel by running the macro "CloudProp": To conserve time, a macro is provided on the worksheet to plot the relationship between Cloud Top Pressure and Cloud Optical Thickness for your storm. At the main menubar in Excel, click on the "Tools" menu, move the mouse down to "Macro >" and across to "Macros..." and release. The Macro window will appear. Select the macro "CloudProp". Click on the "Run" button. You will see Excel automatically produce a graph of your data. You may also produce a similar scatter plot with any other data analysis program available to you. Compare your results with the prediction you made in the hypothesis section earlier in the module.
   
   
6. Save the graph as a Web page: You may convert your Excel spreadsheet to a Web page in order to share your results with others. Instructions are provided below. If you do not wish to create a Web page at this time, please go on to the results section.
   
   Excel allows you to directly save your file as a Web page: Click on the "File" menu in Excel, move down to "Save As Web page", and release the mouse button. Follow the instructions on the screen and make a note of the directory to which you are saving.

After you have finished creating your Web page, please go on to the final section of the module to interpret and communicate the results of your investigation.