Part 4—Compare Two NEO Datasets in ImageJ
Step 1 – Learn about the Carbon Monoxide Dataset
Carbon Monoxide (CO) is monitored globally by an instrument called MOPITT (Measurements of Pollution in the Troposphere) on the TERRA satellite. You can access its data from NEO, under the Atmosphere tab. You can read about this dataset in the NEO interface, just as you read about the Aerosol Optical Thickness dataset in Part 2.
The map of CO concentration depends on the underlying source of the CO. If the CO source is a constant emitter, then the amount should not change dramatically in location, size, or concentration from month to month. For instance, a large industrialized area with many factories emits a fairly consistent amount of CO from month to month. A natural source of CO, such as a region that experiences sporadic brush or forest fires, emits CO on an intermittent basis, until the fires are extinguished or until they naturally burn themselves out.
Step 2 – Download a CO stack and Load into ImageJ
- As you did for the Aerosol Optical Thickness (AOT) dataset in the NEO interface described in Part 2, you could download twelve images for 2008 monthly CO data from the the Carbon Monoxide (MOPITT) dataset under the Atmosphere tab. To save time, if necessary, the data has been downloaded and then imported into ImageJ to create a stack for your use.
- The resulting stack was saved as a .TIF file. Download the CO stack (TIFF 8.9MB Jun24 10) to your computer.
- Create a folder named CO2008 to hold the 12 images you will download.
- Go to the NASA Earth Observations (NEO) homepage .
- Click the Atmosphere tab along the bottom of the image window.
- In the list of Atmosphere datasets, click the Carbon Monoxide MOPITT dataset.
- Select and download to the CO2008 folder the December 2008 monthly average CO data, naming the jpeg file in a numeric sequence, just as you did for the AOT animation.
- Before you Get Image, be sure to Resize to a resolution of .5 degree.
- Repeat the downloading process for all 12 monthly average CO data.
- Upload the 12 files from the folder CO2008 into ImageJ using File > Import > Stack Sequence.
- Click the first file in the pop-up browser and select Open.
Step 3 – Create a Parallel Animation of AOT and CO data for 2008 in ImageJ
Animating or stepping through a series of images in sequential time order allows you to begin to figure out what natural or anthropogenic phenomenon is creating the spatial and temporal patterns that you see. The first step is usually visual inspection of the data. Try to notice if there are geographic areas which have high values in both datasets. Look at the months as seasons and determine if there are times of the year in 2008 when values are very high or very low.
- Here (TIFF 8.9MB Jun16 10) is the AOT stack again. Launch ImageJ and open the AOT2008.tif file, if it is not already open.
- Click on the AOT window. You can step through each month which is called a "slice" by typing > to go forward, and < to go back, or use the scroll bar on the image.
- Load the CO2008.tif file that you downloaded in Step 1 into ImageJ. Do not close AOT2008.tif.
- Go to Image > Stack > Tools > Combine...
- Check the "Vertically" box in the pop-up that names the two datasets you wish to combine.
- Now both datasets are loaded into one window, on top of each other and showing the first image of the stack. Run the two animations and see if you notice any patterns of plumes or identical months where there are high or low values in both the AOT dataset and the CO dataset.
- Use the Next Slice (>) and Previous Slice (<) keyboard shortcuts to step through the combined stack, one slice at a time, comparing the two datasets month by month.