COMET Workstation Tutorial Exercise

GEMPAK Analysis and Rendering Program (GARP)

 

1) Log on to the Hewlett-Packard Workstation:

  1. To log on: Ensure cursor is all the way to the left of the username box.
  2. Enter your login name <return> and your password <return>.

2) Initiate GARP:

  1. Click on the right mouse button outside of the X-term window and hold it down. Drag the arrow down to Met Applications, over to NTL and then onto Current (the other choices are dates of cases you will study later).
  2. You will see a small menu (the NTL menu) appear on the far left of the screen. Click once on garp with the left mouse button.

3) Load an Image:

  1. Drag the cursor along the icons to see what is available.
  2. Click once (with the left mouse button) on the leftmost icon (Radar and Satellite Data).
  3. A window will appear with choices of satellite and radar data.
  4. Click once on GOES-8_UNI (UNI=Unidata images, RAM=RAMSDIS images, Composite=Global WV composite, nids=Level II and/or III radar from WSR88-D at sites determined by COMET staff, nowrad is the radar composite from WSI Corp. level III, base reflectivity only) in the Data Source box.
  5. Data Scale gives choices of resolution, Click (with left mouse button) on 4km.
  6. Product Types tells what channels are available at the above resolution; click once on IR4_10.7.
  7. Available Times will have highlighted the 6 most recent images, the scroll bar on the right allows you to go back in time. Click once on the last image in the box.
  8. Click once on Display & Close.

4) Auto-Update

  1. Auto-update is activated by clicking on Time in the main menu bar then on Auto Update. Click on the toggle button to start up auto-update and adjust the update interval with the slider bar. (For more details, see the GARP User's Guide referenced at the end of this tutorial)
  2. Click on Apply then Close.

5) Become Familiar with the information displayed: 

  1. Note the temperature scale on the left for Infrared images.
  2. Move the cursor around the image and note the position information (lat/lon) and the Raw [pixel values] brightness and the Brightness temperature on the status bar along the bottom of the window.
  3. Now click on "Area" on the menu bar at the top of the screen. Choose an interesting region (Northwest, Southwest, etc.). To return to the full image, click on "Area" again, and then DEFAULT.
  4. Distance Function: Click (left mouse button) once anywhere on the image. Note the large red cross-hair. This is an anchor point. Move the mouse around and notice the distance read-out in the lower right hand corner of the status bar. Also included is information on the azimuth and range in relation to the location of the cross-hair. If you want to remove the cross-hair from the screen, click left mouse button while holding down the control button.
  5. To change preferences on the status bar, place the mouse on the bar and click the right button. A window will be displayed. Units may be changed by clicking on the appropriate box and selecting the desired unit. Items may also be removed from the status bar. If the item is checked, it will be displayed.

6) Rubber Band Box Function or Click twice to Zoom:

  1. On the same image that you have displayed, put the cursor near an area of interest.
  2. Hold down the left mouse button and move to encompass your area of interest and release the mouse.
  3. The image will be "zoomed" to the box dimensions. To return to the full image, click on "Area" and DEFAULT.

NOTE:  You may also click on "Area" and Previous to go back one zoom.

  1. Alternatively, you can make two "quick" clicks of the left mouse button and you will magnify X2 centered around the place where the cursor arrow is situated.

7) Load a loop of images.

  1. Click once on the Reset icon, and then click on the Radar and Satellite icon again.
  2. Click on the nowrad, US_8km, and BREF buttons.
  3. Select at least 5 images. This is done by putting cursor over the first image selection, press and hold the left mouse button down and drag cursor down the list until images are highlighted. Release the mouse button and click on Display & Close.
  4. Use the "VCR" buttons at the upper right of the screen to animate. Experiment with different speeds by pulling the speed button back and forth. Fade the image with the fade button (this will be even more useful when we overlay graphical data).
  5. Click on the "Options" button at the top of the screen in the menu bar. Click on Overlays and then Station. Click on the box next to "Type" and select NEXRAD. Click on Station ID and select Name. Click on Display and then Close. Fade the image to see only the site labels.
  6. Click again on options and select animation. Within this window you can select different animation speeds, remove a bad/blank frame, or customize the speed yourself. To remove a frame, click on the frame number in the frame box. That frame will be highlighted. Animate and notice that frame has been removed. Experiment with the other options.  Click on the Reset icon.
  7. Now loop images at 2-hour intervals. Click on the Radar and Satellite icon again, GOES-8_UNI, 4km, IR4_10.7. Click on the first desired image, then hold down the CTRL key and click with the left mouse button increments of 2 hours. Click on Display & Close. NOTE: If you need to go outside the original box, using the scroll bar on the right, DO NOT SCROLL WHILE HOLDING DOWN THE CTRL BUTTON. Animate the images with the "VCR" buttons.
  8. Now change the enhancement curve. Stop the animation. Click on the menu bar "Options" at the top of the screen. Click on Enhancement. Use the left mouse button to highlight "ir_upc2." Experiment with the Fade and Roll buttons in the middle of the window (reset to the default Fade and Roll values using the "Reset Lut" button. (Note: You can move the window around the screen by placing the cursor arrow near the word "enhancement" and holding the left mouse button down while dragging the window to different position). Click on the invert button, and then click it again to toggle it off. Click on the "gray" enhancement. Close the Enhancement window. Leave your loop loaded.

8) Overlaying Observational Data.

  1. Click on the surface observational data icon. Note that you can choose METAR, mesonet (not always available), or ship and buoy data. If time matching is activated, the only times that will be displayed are the times matched to the images currently loaded. To enable time matching, click on time in upper left corner, select Time Matching and high-light the circle next to Strict. Close this window. (For more details on Time Matching, see the GARP User's Guide)

NOTE: In the time matching menu, there are three options. Strict means data must reside within a pre-defined time interval for a time match to occur. Closest will match the closest time to the image that is loaded. None will disable time matching all together.

  1. Within the Surface Ob window, click on the Station Layout box to see what parameters will be plotted. Parameters may be changed by selecting from the scrolled parameter box. With the middle mouse button, click and drag the parameter to the desired location. Close this box.
  2. Click on Display & Close at the bottom of the remaining window. When graphics are loaded, click right mouse button in window. Click the second circle in Font Size and Symbol Size, the fourth from left in Symbol Packing and click on Apply. Notice how more sites were added to the display. If you zoom in on an area, the resolution of the surface data will increase even more.

NOTE: The font will remain the size it has been changed to when you move on to another graphic, it will not default back to the original size. This is true for all the parameters changed in this menu.

  1. This may also be animated. Click on the clear icon.

9) Upper Air Data.

  1. Click on the UpperAir Data icon. Click on the station layout box. Note the parameter toggles.
  2. Click on the close button.
  3. Click on the pressure level box. Click on 850 in the small upper left-hand corner window. Highlight the 00Z and 12Z files for the last two days.
  4. Click on Display & Close box at the bottom. Animate your graphics.
  5. Plot the upperair data on a satellite image.   Press the clear icon.
  6. Click on the Radar and Satellite icon, choose GOES-8_UNI, 4km, IR4_10.7. Load the past two days 00Z and 12Z images using the control key. Click on Display and Close.
  7. Click on the UpperAir Data icon. If time matching is still activated, only the files that match the images will be displayed. Select Display & Close.
  8. Fade the image so that the graphics remain. Fade back in the image. (Note: For now only the image can be faded). Click on the Reset icon.

10) Plotting Soundings

  1. Click again on upper air data. Click on box next to type and select vertical.
  2. Click on the time and station desired. Click on Display and Close.

11) NIDS Data

  1. Click on the Radar and Satellite icon. Click on nids. All the currently available 88d radar sites will appear. They are labeled by their 3-letter identifier.
  2. Select one of interest. You will see the different fields that are available for the particular site. You may need to scroll to see the full list. Not all fields are available for all radar sites. (NOR= 1 km base reflectivity, NOV= velocity, NOZ = 2 km base reflectivity, NCR= composite reflectivity, NOS= Storm Relative Motion, NTP = Total Prec Accumulation)
  3. Select field and times desired and select Display & Close.
  4. You may overlay data just as you did on the satellite.

12) Gridded Data.

  1. We'll start with gridded data alone, and then practice with some overlays.
  2. Click on the Model Plan Proj. icon. Look over the window that pops up.
  3. Click on box that has eta. Note what other models are available. Choose the ETA model, then click on level 1; and then click on 500 in the Model Levels window and close window.
  4. Click on the most recent model run F30 forecast. Note: If you are going to load model data over imagery, time matching will assist you here also.
  5. Note the lists in the next two columns. These are GEMPAK functions/variables that can be plotted. (You can type in your own, an example follows). 
  6. Highlight isotach_kts-1 in the Scalar field window and notice the MAG (KNTV (OBS) ) in the longer window near the bottom (a.k.a.: "The function box").
  7. Click on the More >> box at the bottom right-hand corner of the window. This window allows you to change the line type and add color fill. It also allows you to change the number of labels on the contours, add high/low symbols and choose between barbs or arrows for vectors.
  8. Click on the Label box and set the label for every line.
  9. Click on the Color Fill box in the Fill area (right side of window).
  10. Click on Table and click on table 2.
  11. Type in 10 for the interval, 30 for the minimum, and 100 for the maximum. Click on close at the bottom.
  12. Click on Display & Close in the lower left-hand corner of the window.
  13. Click reset icon.

13) Looping Gridded data overlain on Imagery and Rubber Band Boxing:  

  1. Click on Radar and Satellite icon. Click on GOES-8_UNI, 4km, IR4_10.7. Using the control key and left mouse button, click on last night's 00Z and this morning's 06Z and 12Z images. Load the images. Make sure you've "de-selected" any images that are automatically highlighted.
  2. Click on Model Plan Proj. Icon Time matching, if activated, should have selected the appropriate Date/times to match your imagery. Click on the scalar field, hght. Click on Display. Put your cursor in the box with the Level and click, this activates the box. Now type: 500:1000 . This establishes a layer instead of a surface.
  3. Click on thickness in the scalar field box. Then click on the More >> button at the lower right of the window. In the Contour area, click on the Type: box and change solid to medium dashed. Close the More >> window. Click on Display.
  4. Reset your level to 1000. Click on the scalar MSLPress. Click on Display and Close.
  5. Practice fading an image. Practice looping the series.
  6. Use the rubber band box function to zoom in on a place of interest.

14) Macros 

  1. Select Model Plan Proj. Icon Under scalar select box displaying General.
  2. The available Macros are displayed. Select desired group. The fields available will be displayed in the scroll window.
  3. Select Macro and Display & Close.
  4. Since multiple fields are loading, it will take a few minutes to complete.
  5. Click on the legend at the bottom of the screen to toggle fields on and off.
  6. Continue experimenting with the Macros.

15) Exiting GARP and NTL and Workstation. 

  1. Click "File" from pull-down menu.
  2. Click "Quit".

Also visit the GARP User's Guide available here or by selecting "help" in the upper right corner of the GARP display window. You will find details about features such as "Auto Update", "Graphic Toggling" and "Time Matching".

Tutorial on AWIPS

Tutorial on Vis5D

Tutorial on Weather

Last updated 15 February 2002

MSC/COMET Winter Weather Course