Background

In 2002, fire fighters had their hands full—the National Interagency Fire Center reported that 88,458 separate wildfires burned approximately seven million acres of land that year. The total area burned was almost twice the average area that burned each year over the previous 10 years.

In Arizona, the Rodeo and Chediski fires both started in late June of 2002. The two blazes spread through the Apache-Sitgreaves National Forest, eventually merging into a single fire that grew to be the largest in Arizona history. By early July of 2002, the fire had burned over 450,000 acres of forested land.

Objectives

Use the RangeView website to…

• View the effects of the 2002 Rodeo-Chediski Fire and compare the 2002 greenness to the previous year
• View the effects of the recent Aspen Fire and look at the difference in greenness between the fire and non-fire periods

Tools

This exercise uses the AVHRR Dynamic Animation Tool (link opens in separate window).

To find the tool without the direct link:
     1) In your internet browser, go to http://rangeview.arizona.edu.
     2) Click on “Dynamic Animation” in the Tools box on the home page.

Exercises

Exercise 1: Identifying the Rodeo-Chediski Fire

In this exercise, you’ll examine evidence of the Rodeo-Chediski fire in “greenness” images. The images are produced from data gathered by a satellite instrument called the Advanced Very High Resolution Radiometer (AVHRR). In general terms, greenness measurements indicate the amount of live vegetation covering the ground. Individual images in the animations represent the average greenness of the area over a fourteen day period. By comparing greenness images of the same place from one time period to another, “difference” images can be produced to show if an area is more or less green than it was before. These difference images can be used as a rough indicator of a forest’s health.

Setting Up the Animation:

1. At the top of the window, click on the Zoom To drop-down menu and choose Arizona.
2. In the column on the left, scroll down and click the FS Land Layer and Label check boxes. Click Refresh.
3. Click the ZoomIn button at the top of the window then click on the left map where the “Sitgraeves National Fores” label appears. Click twice to zoom in.
4. Select Greenness (NDVI) as the data type for the left image viewer, and Difference from Last Year’s NDVI for the right image viewer. Select 2002 as the year for both viewers. Click Refresh.
5. Look at the image color scales to understand what the different colors on the images show. (What part of Arizona has the most green vegetation? What color is an area that is less green than is was the year before?).
6. Uncheck the FS Land Label checkbox. Check the Cities/Towns Layer and Label check boxes. Click Refresh.
7. Note the locations of Heber and Pinetop. You’ll look for evidence of the fire in the area between those towns in the animation you’re about to produce.
8. Uncheck the City/Towns Label checkbox so the names don’t cover the data.
9. Click Animate to generate two sets of images showing this area through 2002.
10. Watch the animations carefully to look for evidence of the Rodeo-Chediski fire. Use the step forward and step backward buttons along the top of the window to examine single images.

Interpreting the Images:

1. Could you tell when the fire occurred? How?
   

2. What is the date of the image where you first see evidence of the fire?

3. In which image (date and type) do you think the fire is most obvious?

4. In the images just before the fire, was the area where the fire occurred more green or less green than it had been in the previous year?
   

5. Can you detect smoke from the fire in either animation? How?
   

6. Describe the appearance of the fire scar that remained after the fire. How long after the fire can you still detect the scar?
   

When you're finished, click the yellow Back button in the top left corner of the screen to prepare for the next exercise.

Exercise 2: Identifying the Aspen Fire

The Aspen Fire started on June 17, 2003 in the Santa Catalina Mountains northeast of Tucson. Before it was finally extinguished in mid-July, the fire had burned 84,750 acres of land and destroyed 333 structures. Most of the structures were summer cabins, second homes built within the forest so their residents could enjoy the cool, high-elevation forest environment.

Setting Up the Animation:

1. At the top of the window, click on the Zoom to drop-down menu and choose Arizona.
2. Choose Greenness (NDVI) as the data type for the left image viewer, and Difference from Last Period’s NDVI for the right image viewer. Select 2003 for the year for both viewers. Click Refresh.
3. In the column on the left, check the Highways Layer and Label check boxes. Click Refresh.
4. Click the ZoomIn button at the top of the window. Click twice on the area where I-10 and I-19 intersect. Northeast of this intersection, focus on the triangle-shaped area with high greenness values. This is Mt. Lemmon where the Aspen fire occurred. Click twice more on Mt. Lemmon to zoom in.
5. Click the Roads Layer check box to show the Catalina Highway that ends near the town of Summerhaven. If you understand contour lines, you might also want to turn on the Contours (500 m) Layer to show the general shape of the mountain.
6. Click animate to produce the animation. Examine the animations frame by frame to look for evidence of the Aspen Fire and answer the following questions.

Interpreting the Images:

1. When did you first see evidence of the fire.

2. What details of the fire are more visible in the difference from last period’s NDVI animation?
   

3. Where are the most notable effects of the fire in the July 15th image?
   

4. Where are the most notable effects of the fire in the July 29th image?
   

5. Each pixel in an AVHRR image shows an area of 1 square kilometer. Use this information to estimate the size of the fire in the July 1 image.