Studying Topography, Orographic Rainfall, and Ecosystems (STORE)

Transcription

1 Studying Topography, Orographic Rainfall, and Ecosystems (STORE) Introduction Basic Lesson 3: Using Microsoft Excel to Analyze Weather Data: Topography and Temperature This lesson uses NCDC data to compare mean annual precipitation for weather stations along the Bay Area/Sierra profile against the elevation of each station in meters above mean sea level (MSL). Students compare ground surface temperature lapse rates with the atmospheric lapse rates to see how they differ and why. Students also learn to read, use and analyze data contained within a GIS database file in Microsoft Excel. Objective To enable students to learn how to work with GIS shapefile data (e.g., database file) in Microsoft Excel and to better understand temperature lapse rates (first introduced in Basic Lesson 1). Lesson Duration 1 class period, 45 to 55 minutes Requirements Microsoft Excel Downloaded and unzipped ArcGIS Explorer files for STORE GIS-intensive lessons folder. Note this folder contains map layers, add-ins and function cards. Part 1 - Open GIS database file in Microsoft Excel 1. Start Microsoft Excel. 1

2 2. Once the program opens, click the Excel icon at the top left and choose Open. 3. Navigate to the California folder contained within the ArcGIS Explorer files for STORE GIS-intensive lessons folder. Select dbase Files (*dbf) from the pull down menu at the bottom. 4. Select ca weather stations.dbf and click Open. The *.dbf file is a tabular database containing spatial (i.e., latitude and longitude) and other information about a shapefile. 1 In the case of ca weather stations dbf file, the other information includes station name, temperature, precipitation, snowfall, etc. The dbf file is one of the elements of the shapefile that was used to locate the weather stations on the ArcGIS Explorer map in Basic Lesson 2. 1 A "shapefile" is actually not one file a set of interdependent files that store the geometric location and attribute information of geographic features. Geographic features in a shape file can be represented by points, lines, or polygons. 2

3 5. Your Excel file will now be populated with the attributes of the California weather stations. 6. To change the column widths automatically to fit the contents so you can see the complete column headings: a. Select all the columns b. On the Home tab, in the Cells group, click Format c. Under Cell Size, click AutoFit Column Width. Your table will now look similar to the view below. 7. It s very important to save the file to an Excel format before continuing. Click the Excel icon at the top left, choose Save As, then Excel Workbook. 8. Navigate to the California folder and save the file as ca weather stations.xlsx. 3

4 Part 2 - Plot temperature vs. elevation, calculate and compare temperature lapse rates Within the troposphere, temperature normally decreases with increasing elevation. In some circumstances, cold air is trapped near the ground and temperature increases with elevation. This is called an inversion. The temperature lapse rate is the rate at which a parcel of air cools as it rises upwards above sea level. In this part of the lesson, you will plot the temperature in July at each weather station against the station s elevation above mean sea level (MSL). You will use this plot to calculate the temperature lapse rate. The temperature lapse rate is defined as the change in mean daily temperature (in degrees Celsius) for each 1,000 meter of increase in elevation above MSL. Once you are finished with this exercise you will compare your calculated ground level temperature lapse rate with a temperature lapse rate from atmospheric temperature recordings taken by a National Weather Service (NWS) balloon. The temperature lapse rate of the atmosphere is measured by the National Weather Service (NWS) using meteorological balloons that are released twice daily at over 100 locations across the United States. The instructions below will guide you through how to plot temperature versus elevation. 1. Sort the elevation values to appear from lowest to highest by selecting the cells of elevation data. On the Data tab click on Sort. 2. The Sort Warning window may appear. If this happens choose Expand the selection. 3. The Sort window will appear. 4

5 4. Under Column pull down the Sort by menu and choose Elevation. 5. Under Order pull down the menu and choose Smallest to Largest. 6. Your table will appear as below with elevation data sorted from smallest to largest values. The JulAvg column lists July Mean Monthly Temperature in degrees Fahrenheit at each of the weather stations. In order to compare the temperature lapse rates at the weather stations with those at Andrews Air Force Base in July, you need to convert the weather station temperature values from Fahrenheit to Celsius. To do this in Excel, you will (a) create a new column for the July average temperatures in Celsius, (b) use this new column to plot the relationship between temperature and elevation, and (c) calculate the temperature lapse rate. 7. Insert a new column I to the right of the JulAvg column and label it JulAvg_C. Convert JulAvg values from to Celsius and put the new vales in the JulAvg_C column. To do this conversion, type this formula into Cell I2: (=(H2-32)*5/9), then copy cell I2 into the remaining cells for the weather stations (i.e., cells I2-I6). The formula represents this conversion equation: Celsius = (Fahrenheit -32)*5/9. Now you will get ready to plot the stations' average July temperature values in Celsius against their elevations above mean sea level. Then you will calculate the change in mean daily temperature ( C) for July for each 1,000 meter of increase in elevation. 5

6 8. On the Insert tab in the Chart group click on Scatter. 9. Pull down the Scatter menu and scroll over the different Scatter plot options until you see Scatter with Straight Lines and Markers. Choose Scatter with Straight Lines and Markers. 10. A chart will appear below the data. This chart will either be blank or populated with data. 11. In order to display the data you want in the chart, right click within the blank chart area and choose Select Data. 6

7 12. The Select Data window will appear. Under the Legend Entries (Series) click on Remove to remove data presently selected. 7

8 13. Under the Legend Entries (Series) click on Add. 14. The Edit Series window will appear. 8

9 15. Place your cursor in the Series name: space. You will see a flashing cursor bar. 16. Click inside the JulAvg_Celsius column heading cell. This column displays the average July temperature in degree Fahrenheit for each weather station. 17. You will see that the Series name has now been populated. 9

10 18. Place your cursor in the Series X values: space. You will see a flashing cursor bar. 19. Select all the values in the Elevation column. You will notice that the Series X values space populates as soon as you select the values. 10

11 20. In the Series Y values: highlight {1} using your mouse. 21. Select all the values in the JulAvg_Celsius column. You will notice that the Series Y values space populates as soon as you select the values. 11

12 22. Click OK to dismiss the Edit Series window. 23. Click OK to dismiss the Select Data Source window. 24. Your graph will look similar to the view below. 25. Label the x horizontal axis. Be sure the chart areas is selected. Click on the the Layout tab under Chart Tools. Within the Labels group click on Axis Titles. Choose Primary Horizontal Axis Title and then choose Title Below Axis. 12

13 26. Your graph will now look like the view below. 27. Edit the axis title by selecting Axis Title and typing Height above mean sea level (meters). Your graph will now look like the view below. 13

14 28. Label the y vertical axis. On the Layout tab in the Labels group under Axis Titles choose Primary Vertical Axis Title then Rotated Title. 29. Your graph will now look like the view below. 14

15 30. Edit the axis title by selecting Axis Title and typing Temperature ( C). Your graph will now look like the view below. 31. Give your graph a more descriptive title. Select the current title JulAvg_Celsius and replace the type with July Temperature vs Height Above Mean Sea Level. Your graph will now look like the view below. You could hide the legend at the right since you have only plotted temperatures for January. If you decide to also plot temperatures for July the legend will help define each series of data. 32. If you d like to resize your graph to accommodate more data you can enlarge it by dragging one of the corners. 15

16 33. Save your Excel file. 34. Use the plot you created to calculate the temperature lapse rate, then round the rate to the nearest tenth decimal place. The temperature lapse rate is the change of air temperature in Celsius per 1000 meters of change in elevation (i.e., ºC/1,000m) 35. The NWS radiosonde balloon records atmospheric temperature within the troposphere while the temperature recorded at the weather stations is representative of ground level temperature. Figure 1, below, shows temperature ( C) plotted against height (meters) from records of a NWS radiosonde balloon released at Edwards Air Force Base, CA on August 4, These radiosonde data show that the atmospheric temperature decreased by about 7.3 C per 1,000 meter of elevation rise m, 23.4 C 10.0 Temperature ( C) m, 35.9 C Height above balloon release point (meters) Figure 1. Integrated Global Radiosonde Balloon Release, Edwards AFB, CA (August 4, 2010) Question 1: How does the lapse rate from temperature recordings by the NWS radiosonde balloon compare to the lapse rate from temperature recordings taken at the Weather Stations? Which lapse rate is faster and why? 16

17 36. The graph below (Figure 2) shows temperature ( C) plotted against height (meters) from records of a radiosonde balloon released from Edwards Air Force Base on February 2, Calculate the temperature lapse rate. Round to the nearest tenth decimal place m, 5.0 C 10.0 Temperature ( C) m, 50.5 C Height above mean sea level (meters) Figure 2. Integrated Global Radiosonde Balloon Release, Edwards AFB, CA (February 2, 2010) Question 2: Review the temperature lapse rates recorded by the balloon release at Edwards AFB in August and in February. How does the temperature lapse rate for summer (e.g., August) compare to the temperature lapse rate for winter (e.g., February)? Which lapse rate would you expect to be faster and why? Additional Information Learn about weather balloons and watch a weather balloon being inflated and released, then listen to the signal from the instrument (radiosonde) attached to the weather balloon as it transmits data back to the ground where the data is plotted on a computer. See to learn about or view a weather balloon. 17