High res integrating socio economic data and biophysical data
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This document provides instructions for integrating census and weather data to understand how weather events impact populations spatially. It describes downloading cyclone track data for 1999 from India, precipitation estimates from NASA, and population density data from SEDAC. The precipitation and population rasters are then integrated through raster calculation to estimate effects of a 1999 cyclone that impacted eastern India.
High res integrating socio economic data and biophysical data
- 1. Integrating socioeconomic data and biophysical data In this exercise we will integrate census data and weather data to get insight into how the effects of a weather system might be distributed spatially. Along the way, we’ll point out several key data resources available online, as well as important tools in ArcMap for integrating datasets. 1. In 1999, a number of strong cyclones hit the eastern coast of India. Go to http://weather.unisys.com/hurricane/ and select “North Indian” to navigate to the “Indian Ocean Cyclone Tracking Data by Year” webpage. Click “1999” to see the paths of cyclones that year. 2. We’ll focus on the fourth cyclone. Scroll down the page to see the exact dates when the storm was a cyclone.
- 2. 3. By clicking on “Tracking information” you can access data on the position and wind speed of the cyclone through time. That might be a very useful resource for certain research applications. For this exercise, however, we are only interested in the dates. They are 15-18 October, 1999. Now go to the TRMM Online Visualization and Analysis System website: http://disc.sci.gsfc.nasa.gov/precipitation/tovas/. This website is a portal to precipitation data records. Scroll down and click on the link to “Daily TRMM and Other Rainfall Estimates”.
- 3. 4. In the map, draw a bounding box that includes most of eastern India. Alternately, you may enter N E S W coordinates. 5. In the next panel, add the cyclone dates: 15 October 1999 – 18 October 1999. In the “Select Visualization” panel, select “Lat-Lon map, Time-accumulated”. 6. Click “Generate Visualization”. This may take a minute. A heat map of accumulated precipitation will appear.
- 4. 7. Click “Download Data” and on the next page, select the “ASC” box for the “Two Dimensional Map Plot”. Then click “Download in Batch” 8. On the next page, click the tar.gz file to download it. It should be a relatively small file. Unzip the file and open it in a text editor.
- 5. 9. Looks a little messy - we’ll fix that. Delete everything up to (and including) “(Lon: 76.375E - 92.875E)”. The text should begin with “latitude longitude precipitation”. Save and close the file. Open excel, and import the text file. This dialog box will appear: 10. Select “fixed width”, and click “Next”. Make sure the breaks are between the columns, and click “Finish”.
- 6. 11. Delete the second column. Then save the file. Sometimes ArcMap has trouble importing xlsx files. Save the file as an Excel 97-2003 Workbook. 12. Close Excel. Open ArcMap. Add the Excel file as a map layer.
- 7. 13. Right-click on the layer, and select “Display X-Y Data”. 14. Change the “Z field” to “precipitation” and click OK.
- 8. 15. The lattice of points that appears represents a sample of precipitation estimates. We will now interpolate the values between those points. Using the “Search” function, find the “Kriging (Spatial Analyst)” tool. Before clicking on it, make sure that Spatial Analyst is enabled (“Customize” “Extensions”). In the “Kriging” dialog window, select the precipitation layer, select “precipitation” as the “Z value field” and chose a name and location for the output file. Also, change the “Output cell size” to “0.0083333333” (more on that later). 16. Click “OK”. The interpolation data will appear. You may wish to unselect the TRIMM point data to see it better.
- 9. 17. Now we have interpolated accumulated precipitation for a cyclone that hit the eastern coast of India in 1999. How many people were affected? We’ll now add another dataset to help put this weather event in more context. The NASA SEDAC website is a very good resource for a range of socioeconomic and biophysical data. We’ll download population data for India. Go to http://sedac.ciesin.columbia.edu/data/set/grump-v1-population-count/data-download. Choose “India”, “Population Density Grid”, “Grid”, “30””, and “2000” from the fields. When you click “Download” you will be prompted to log in, or register.
- 10. 18. Once you have logged in, and clicked “Download”, the zipped data files will begin to download. Unzip them, and open the dataset in ArcMap. 19. Now we’ll do a rough calculation of the values of both raster layers to get some insight into how the effects of the storm’s heavy precipitation might have been distributed across the landscape. Using the search utility, open the “Raster Calculator (Spatial Analyst)” tool. For this exercise we are going to simply multiply the values of the population density raster cells by the values of the precipitation raster cells. However, a more deliberate analysis would include several intermediate steps to normalize or otherwise transform the distribution of cell values for both rasters, so that a calculation would be more meaningful—and the calculation itself might not necessarily involve multiplication.
- 11. 20. Create an equation by clicking on one raster layer, then the “*” button, then the other raster layer. The equation should look like this: "induds00ag" * "precip_interp". Then choose a name and location for the output file. Click OK. 21. If you wish, you may change the color of the new raster layer, set it to be semi- transparent, or change the symbology in some other way. You may also wish to unselect the precipitation layer.