SatMet Labs PageSatMet Lab Exercise
GOES Image Observation/Interpretation
Jack Dostalek CIRA/NESDIS-RAMM
The purpose of this lab is to illustrate the capabilities of GOES satellite imagery with a variety of cases which include unique mesoscale weather phenomena and surface features. It is intended to provide experience in the use of multi-spectral imagery. Each case includes one or more image sequences (loops) which are to be carefully studied to see what specific features can be observed. Instructions are given for entries to be made in the workstation’s "Command Line Window." A few questions are given with each case to aid in image interpretation. A summary is given to highlight some of the objectives and observed satellite features. However, your image analysis and discussion should not be limited to the questions and summaries provided here, since the imagery reveals many additional interesting phenomena. Remember also that accurate satellite imagery interpretation depends on acute satellite imagery observation, which includes viewing imagery from all of the available channels and/or products.
Initial Set-up Instructions:
To start the RAMSDIS-X session, move the cursor to an xterm window and type:
ramsdis -fr 198 -imsiz 480 640
This will bring up an image window, a text window, and a command line window.
Then, move the cursor into the command line window and type:
BATCH START.CMD
You are now ready to begin the laboratory exercises.
Some McIDAS commands which might be useful:
LB 1 2 : Sets loop bounds from frame 1 to frame 2.
Alt-L : Starts and stops loops set up by the LB or LS commands.
DR # : Controls the time spent on each image in the loop. The smaller the number (#) the faster the loop speed.
Alt-A : Moves loop ahead one frame.
Alt-B : Moves loop back one frame.
Alt-O : Changes current frame and loop bounds between opposite loops.
MAPL VH: Draws map background over the current loop. Set loop bounds first. For maps not over the U.S., use MAPL OUTLHRES.
You may want to refer to the INTRODUCTION TO RAMSDIS-X handout for more information on the above commands as well as for other commands you may wish to use.
Other :
Multiple keys which are to be struck simultaneously will be separated by a ‘-‘. For example Alt-L above.
Case No. 1 Great Lakes
Part 1: 3-min interval images are shown over the Great Lakes on Nov. 14, 1995. In addition to the visible loop there are corresponding loops of IR Ch 4 (10.7 m m), Water Vapor (6.7 m m), and Reflectivity Product.
Instructions:
Ctrl-F4 to load images. Loop bounds automatically set to frames1-38.
Frames 1-38 Visible
Frames 100-137 Reflectivity product
Frames 39-76 10.7 m m
Frames 138-175 6.7 m m
Visible and Reflectivity opposite
10.7 m m and 6.7 m m opposite
The LS command is useful for creating a loop which contains imagery from the various channels for a particular time, allowing you to compare the different channels and products with each other. For example, type LS 25 63 162 124 for a loop of the VIS, 10.7 m m, 6.7 m m, and Reflectivity product for 1815 Z.
Questions:
1. What can you say about the flow pattern over the region?
2. Can you identify regions of snow cover and what can you say about their appearance in different areas and compared with clouds? Be sure to use the various channels and products.
3. Which loop(s) is(are) most helpful in analyzing cloud layers over MN?
4. Find areas of liquid water cloud and ice water cloud.
5. Note areas of different types of cloud cover (i.e. cumulus, stratus, cirrus, waves, streets, etc.)
Part 2:
Questions:
Instructions:
Ctrl-F5 to load images. Loop bounds automatically set to frames 1-79.
B: High resolution visible over Lake Huron
Instructions:
Ctrl-F6 to load images. Loop bounds automatically set to frames 1-79.
C: High resolution visible over Lake Michigan
Instructions:
Ctrl-F7 to load images. Loop bounds automatically set to frames 1-79.
Summary:
The Great Lakes region is shown with multi-spectral imagery on a day characterized by broad cyclonic flow, with much of the region influenced by deep cold sinking air. The low-level instability due to the relatively warm lake water has generated lake effect snow bands. Several mesoscale vortices can be observed. Close-up visible loops are shown for Parts 2a-2c.
Case No. 2 Fires in SE US
The Gulf Coast States are shown in a visible loop with corresponding loops of IR Ch 4 (10.7 m m), IR Ch 2 (3.9 m m), and the Reflectivity Product.
Instructions:
Shift-F4 to load images. Loop bounds automatically set to frames 49-63.
Frames 49-63 Visible
Frames 148-162 10.7 m m
Frames 64-78 3.9 m m
Frames 163-177 Reflectivity product
Visible and 10.7 m m opposite
3.9 m m and Reflectivity opposite
Questions:
1. Two smoke plumes over the water near the Gulf Coast can be seen in the visible loop. Can you identify others?
2. Use the 3.9 m m imagery to identify the fires in the region (no need to find them all, but get a feel as to how they appear).
3. How do those pixels show up in the 10.7 m m and Reflectivity Product?
4. There are some dark (warm areas) in the 10.7 m m imagery. Are these due to fires?
5. How well do smoke plumes show up in each loop?
6. What can be said about the surface area near the Miss. River?
Summary:
The multi-spectral imagery reveal numerous "prescribed burning" fires in the agricultural regions of the SE US. The appearance of such fires in the imagery is similar to forest fires, many of which are initiated by lightning strikes in remote Western US locations. The case illustrates the utility of GOES multi-spectral imagery in detecting and monitoring fires.
Case No. 3 Brazil
Rapid interval imagery is shown over a region of South America, which includes portions of Brazil, Peru, and Bolivia. Visible, IR Ch 2 (3.9 micron), IR Ch 4 (10.7 m m), and the Reflectivity Product loops are shown.
Instructions:
Shift-F6 to load images. Loop bounds automatically set to 64-77.
Frames 64-77 Visible
Frames 163-176 3.9 m m
Frames 78-91 Reflectivity product
Frames 177-190 10.7 m m
Questions:
1. Lake Titicaca (large lake along borders of Peru and Bolivia) and a large desert area can be seen to the south of it. Compare the two in the four different products.
2. Note regions with fires. Do you see any noisy pixels in this sequence?
3. Find an example of the following: liquid water cloud, ice water cloud, liquid water cloud changing to ice water cloud and thin cirrus.
Summary: A wide variety of interesting phenomena shows up in this imagery, which includes very unique topographical/surface features for which the multi-spectral data contribute useful additional information. An area with numerous fires is seen in Brazil. A large lake appears very similar to a large desert area at 10.7 m m. Clouds associated with the Andes generate cirrus plumes which advect downstream.
Case No. 4 SST
IR channel loops are shown to illustrate SST (sea surface temperature) patterns near Florida in winter.
Instructions:
Shift-F7 to load images. Loop bounds automatically set to 100-108
Frames 1-9 3.9 m m
Frames 100-108 10.7 m m
3.9 m m and 10.7 m m opposite
The color table applied to these loops was created to show differences in cold objects (i.e. clouds). The ROLL command may be used to move the color table so that the higher color gradient lies over the warmer scenes (i.e. SST). To roll the color table, stop the loop and in the command line window, type ROLL. Move the cursor within the image window until the SST gradients are easily seen. Follow the instructions in the text window for applying the new color table to your loop.
Questions:
1. Identify the main ocean current feature and its temperature characteristics.
2. Do SST patterns show up better at 10.7 m m or 3.9 m m?
Summary:
In the absence of clouds and with an appropriate enhancement, GOES 10.7 m m and 3.9 m m channels can be used to analyze SST patterns.
Case No. 5 Heat Islands
Nighttime loops of IR Ch 4 (10.7 m m) and IR Ch 2 (3.9 m m) are shown over the Midwest in summer.
Instructions:
Shift-F8 to load images. Loop bounds automatically set to 87-91.
Frames 87-91 10.7 m m
Frames 186-190 3.9 m m
10.7 m m and 3.9 m m opposite
You may want to roll the color table here as in the SST section. Look at that case for instructions concerning the ROLL command.
Questions:
1. Locate midwestern cities in the loop.
2. Which of the loops is best for depicting such features?
Summary:
The "urban heat island" effect is revealed by multi-spectral imagery.
Case No. 6 Tornado
April 17, 1995, north-central TX, southern OK, rapid interval imagery of severe thunderstorms. A visible loop is shown with corresponding 6.7 m m, 3.9 m m, 10.7 m m, and Reflectivity Product.
Part 1: Multi-spectral imagery
Instructions:
Shift-F9 to load images. Loop bounds automatically set to 1-33.
Frames 1-33 Visible
Frames 100-132 3.9 m m
Frames 34-66 10.7 m m
Frames 133-165 6.7 m m
Frames 67-99 Reflectivity product
Visible and 3.9 m m opposite
10.7 m m and 6.7 m m opposite
Questions:
1. Which thunderstorm is most likely to be tornadic?
2. What are the characteristic cloud features and motions you can observe in the imagery and which are the indicators of severe thunderstorms?
3. Identify and differentiate the different air masses as seen in the satellite loops.
Part 2: High resolution visible imagery
Instructions:
Ctrl-F2 to load images. Loop bounds automatically set to 83-99.
Frames 83-99 Visible
Questions:
1. Are there any features in the high resolution data, which cannot be seen or are difficult to see on the previous loop?
2. Where and when do you think the tornados occurred?
Summary:
A severe thunderstorm/ tornado case study is shown to illustrate the use of multi-spectral imagery and high resolution/rapid interval visible imagery.
