solo
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solo

Course Number: AT 741, Fall 2004

College/University: Colorado State

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SOLO Overview The NCAR SOLO1 package can be used to display data similar to VCHILL; however, it is also a powerful data manipulation tool. It allows one to clean up data (remove spurious echos), unfold radial velocities, manipulate variables, generate statistics, etc. This writeup provides a bare bones summary of some SOLO features with particular emphasis on unfolding radial velocities. Unfortunately, NCAR does...

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Overview SOLO The NCAR SOLO1 package can be used to display data similar to VCHILL; however, it is also a powerful data manipulation tool. It allows one to clean up data (remove spurious echos), unfold radial velocities, manipulate variables, generate statistics, etc. This writeup provides a bare bones summary of some SOLO features with particular emphasis on unfolding radial velocities. Unfortunately, NCAR does not have any written documentation on the latest version of SOLO so much has to be learned through trial and error. Step 1 Creating Sweep Files The radar data well be working with are stored in binary universal format (UF) files: one for each radar. The UF files contain all the radar data from all the elevation sweeps. SOLO requires that the data from individual sweeps be broken out into separate files. To accomplish this, we use an NCAR translator program xltrsii, which is executed from a script uf2swp. In addition to executing the translator, the script also sets some environment variables to run SOLO. For example, the line setenv DORADE_DIR . sets the current directory as the location where SOLO will be run. If you plan to run SOLO in a different directory, you need to change the path in the script accordingly. To generate sweep files, uncompress the UF file: gunzip file.uf, , where file.uf is the UF file we start with. Then type: uf2swp file.uf. You should now have a series of files labeled something like swp.YYMMDDHRMMSS.radarname.elevationangle_PPI_v1. Caution - SOLO has no undo button, so if you make a mistake you will need to regenerate the sweep files from the original uf file Step 2 Running SOLO: getting familiar with the program (confidence building!) Starting the program To start the program, type soloii at the prompt. If all goes well, you should get a graphical display of the radar PPI data (the lowest elevation angle is chosen by default). Using the top menu By default, SOLO makes a 2 X 2 window display. The parameters that are displayed in each window depend on the order in which they were written out in the original UF file. For example, for TOGA the first 4 parameters are DZ (radar reflectivity), VR (radial velocity), SW (spectral width), and ZT (unthresholded reflectivity). For the purposes of unfolding, we are most interested in DZ and VR. You can change the window configuration by clicking on the Config button and choosing another window display configuration. Keep in mind that we are going to be creating one additional field for unfolding (VT) so you will probably want at least 3 windows (DZ, VR, and VT) the default 2X2 should work fine. To change the zoom, click on the zoom button. You can change the center location of all the windows by clicking on the middle mouse button over the desired location within a window. 1 We are actually using the new SOLOii software Right mouse button Most of SOLOs features can be accessed with the right mouse button. Move the cursor to a window of interest (e.g., VR) and right click the mouse. You should get a menu list of features: Important: when your finished with a menu, always click cancel to get rid of the menu display. Do not simply close the window SOLO will get very upset if you do this and will likely crash or freeze up at some point. Use the sweepfiles button to access all the sweeps that are in the current directory (once the sweepfiles widget launches, click on the sweeps button to view and/or change the sweep file your working on). The parameters and colors button lets you change the color bar and scale of the parameter your viewing. Note that to change the scale, use the center and interval as opposed to the min-max. The view button can be used to change the rings and radial overlay display. The editor button allows you to execute commands and manipulate data (e.g., copying fields, unfolding, eliminate spurious echos). Well come back to this in the next section. The examine button generates a display of the actual data at each gate for number of rays. The starting ray, number of rays, and data fields can all be changed. Click the refresh button to see the results of any changes. The examine menu widget also can be used to display important header information in the radar file: click on display and then metadata. example, For this feature can be used to find the Nyquist velocity. The data widget button generates a display of the window field values (e.g., DZ in window 1) surrounding the location where the mouse was clicked. The display shows the values for the 3 closest rays and 5 range gates surrounding the location of the mouse, as well as the lat/lon/elevation and approximate x,y,z position from the radar. To hide this display, go up to the main SOLO menu under the file button and click the hide data widget button. Step 3 Running SOLO: unfolding radial velocities Copy the VR field The first thing we need to do is create a copy of the VR field to do our unfolding. That way, we can always go back and re-copy the field if we screw up. Use the right mouse button in the VR window and click on editor. In the List of all from each ray commands, select copy <field> to <field>. After clicking, the command should appear in the upper left blank area. Replace the first <field> with VR and the second <field> with VT. The command can then be executed by typing the OK Do it! button. This will generate a VT field for the sweep your working on. Alternatively, you could generate a VT field for all the sweeps in one step by changing the stop time at the bottom of the edit widget to cover the time of the last sweep. Display the VT field After the VT field has been created, you can display it in one of the windows (e.g., the window where ZT was displayed) by right clicking the mouse and choosing VT under the parameters and colors button. Well use this VT window to unfold the velocities. Unfolding velocities Identify an area in the VT field that contains velocities outside the Nyquist interval and need to be unfolded. You can use the zoom button in the top menu of the SOLO display and the center mouse button to move around the display as needed. Right click the mouse in the VT window and choose editor. Now, well identify the region to unfold in the VT window by drawing a boundary around it. In the edit widget, click on the Clear bnd button to make sure that any previous boundary areas are erased. Go back to the main SOLO display VT window. Using the left mouse button, draw a boundary around the region of velocities to unfold. The boundary should end at pretty much the same location where you started; however, its OK if theres a small gap between the starting point and ending point. Note: when drawing the boundary, be careful NOT to cross the zero isodop. If you do this, hit the Clear bnd button in the edit widget and start over. If you attempt to unfold a region that crosses the zero isodop, youll screw up the velocities outside of the region you intended to unfold (recall the example in class). If you do this, youll have to re-copy the VR field for this sweep. After your satisfied with the boundary youve drawn, youre ready to unfold. Go back to the edit widget menu. If there is already a command in the upper left blank area (under the Commands for Each Ray title, erase it either with the clear button or using the keyboard. Pick the forced unfolding in <field> around <real> command from the lower left command box as was done previously for the VR copy procedure. Replace <field> with VT and <real> with the value of the Nyquist velocity. Note if you are unfolding velocities in a region were the surrounding velocities are negative (toward the radar), select the negative of the Nyquist. For example, if the magnitude of the Nyquist velocity is 12.0 m/s and you are interested in unfolding velocities that are embedded within a region of velocities approaching the radar, choose -12.0 for <real>. Choose the opposite (i.e., 12.0) if the folded region is embedded within a region of receding velocities. Click on the boundary button at the top of the edit widget and verify that the Edit inside option is selected. Then, click the OK Do it! button on the left side of the edit widget (just like when copying the VR field). If all goes well, the VT window should display the unfolded region with the velocities now corrected. Continue this procedure for the entire sweep, making sure no regions are left unfolded and do the same for the rest of the sweeps as well.
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