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2.2 Level II Radar
This section describes how to create displays from WSR-88D Level II data. The set of steps include:
2.2.0 Accessing WSR-88D Level II Radar Data
The Level II data is supplied as volume-scan files, each file having all data from one WSR-88D radar for all sweeps for one "time". Unidata Community sites can receive Level II data using the Unidata Local Data Manager (LDM). Archived Level II data is available from the National Climatic Data Center (NCDC) (data from NCDC must be un-tarred).

The files should be stored on your file system with each station's files in a directory (folder) whose directory name is the station 4-character ID (e.g., KTLX for Oklahoma City). In many cases the data files do not have any location information in them and the IDV uses the directory name as a first guess at the station location. Otherwise, use the Radar Location widget to specify the location.

2.2.1 Choosing Level II Radar Data
In the Data Source Chooser window click on the Radar tab and then the Level II tab.
../data/choosers/images/Level2Chooser.gif
Use the file chooser to find the directory which holds the data you want to display. Click on a file name you desire (multiple files can be selected with the Shift or Control keys) or select the latest N files. When you have selected all files you need, click the Add Source button.
2.2.2 Making Level II Radar Displays
The data source is shown in the Field Selector window. Level II data has three moments or data types: Reflectivity, RadialVelocity, and SpectrumWidth. The IDV has several kinds of displays for Level II data. Any of the moments can be shown with any of the displays. Here we will use examples showing reflectivity. Clicking on the "Reflectivity" entry in the Field panel will show the list of available displays in the Displays panel.
images/Level2Selector.gif
2.2.3 2D Displays of Individual Sweeps
Level-II 3D Display
Image 3: Level-II 3D Display
Select the Radar Sweep View in 2D in the Displays panel and click on Create Display. Radar Sweep View in 2D plots the data as an colored image on the base of the 3D display area. This mimics conventional PPI plots on a map.

The Radar Sweep Control allows you to change which sweep elevation you want to see. You can add range rings with the Displays->Add Range Rings menu item. You can modify the range rings with the Radar Range Rings control.

2.2.4 3D Displays of Individual Sweeps
Level-II 3D Display
Image 4: Level-II 3D Display
Select the Radar Sweep View in 3D entry in the Displays panel. Radar Sweep View in 3D plots the data as an colored image, with the data plotted in 3D space at the elevation where the sweep occurred. You can rotate the display to see the three dimensional nature.

You can use this display to merge radar data display with upper air data such as the IDV plots of NOAA Profiler data. Since the Earth is projected onto a flat surface in this display, the sweep has a shape very close to a rotated parabola. The Radar Sweep Control allows you to change which sweep elevation to display.

2.2.5 Pseudo-RHI Displays in 2D and 3D
Level-II 2D RHI
Image 5: Level-II 2D RHI
Level-II 3D RHI
Image 6: Level-II 3D RHI
Select RHI in the Displays panel and press Create Display. RHI plots the data as an colored vertical cross section at the true elevations of the beams in 3D space (bottom illustration). This pseudo-RHI is constructed from several horizontal sweeps of the radar. You may have to rotate the display to see the RHI in 3D.

The beam width is indicated by the vertical extent of each colored vertical stripe, corresponding to a bin beam bin sample. Beam overlap is clear. Position of the RHI in azimuth can be adjusted by dragging the little box on the end of the selector line above the RHI.

The 2D plot of pseudo-RHI (top illustration) is shown in the RHI Control. That control also has an auto-rotate feature. The RHI displays have time animation.

2.2.6 All Sweeps in 3D
Level-II Volume Scan
Image 7: Level-II Volume Scan
Select "Reflectivity" in the Field panel and select Volume Scan (all sweeps) in the Displays panel. Volume Scan (all sweeps) plots the data as 3D field of points colored by value. Each point is a bin value; all sweeps and bins are shown.
2.2.7 Radar Isosurfaces in 3D
Select "Reflectivity" in the Field panel and select Radar Isosurface in the Displays panel. An isosurface is a 3D analog of a contour line. It shows the location of all data with a single data value. Interpolation is used between sweep altitudes in the IDV isosurface plot of Level II data. All data in a volume scan is used. The example shown is the 50 dBZ isosurface from a line of thunderstorms crossing Oklahoma at 1330Z 11 Sept 2003. Vertical exaggeration is 13 to 1.
Level-II Isosurface
Image 8: Level-II Isosurface

 


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