NWS Lubbock Weather Radar (KLBB) Dual-Polarization Upgrade
 
The upgrade to dual-polarization technology for the National Weather Service Lubbock doppler weather radar has been completed!
 
What is Dual-Polarization?
 

Previous radar technology only allowed for the sampling of the horizontal orientation of weather (e.g. rain, hail) and non-weather (e.g. insect, ground clutter) targets.  Dual-polarization technology provides the ability to collect data on both the horizontal and vertical properties of targets, including their size and shapeForecasters will thus now receive better information about precipitation amounts and heavy rainfall in flooding events, hail detection in thunderstorms, and even recognize whether precipitation is in the form of rain, snow, or ice in the winter.   

 
Current KLBB Doppler Radar.
Future Dual-Pol KLBB Doppler Radar.
 
Dual-Polarization Products and Applications
 
In addition to maintaining the current radar products of base reflectivity, velocity, and spectrum width, dual-polarization technology provides for three new base products.  These are differential reflectivity (ZDR), correlation coefficient (CC), and specific differential phase (KDP).  In addition, several new derived products are available, including one for determining the height of the melting layer and one for determining hydrometeor (e.g. water, ice, dust, etc.) classification.  Below are some images showing applications of these products when utilized with current base products.
 

 Tornadic debris being detected by radar.  The high reflectivity and strong rotation in a tornadic supercell thunderstorm can be seen in the top two images with current products.  The bottom-left image shows a minimum in CC (blue area), corresponding to debris being lofted by a tornado.  The bottom-right image shows a void in KDP, where the tornado is located, since KDP is not calculated with a low CC.             NOTE:  This signature WILL NOT improve lead times for tornado warnings.  Rather, it is confirmation that a tornado is on the ground.

 
  Hail being sampled by base reflectivity and differential reflectivity.  Base reflectivity shows an intense precipitation core in a supercell thunderstorm.  Differential reflectivity displays a relative minimum in this same area, suggesting hail tumbling to the ground with rain.
 
  Correlation coefficient can also be used to locate the melting layer in the atmosphere as well as turbulent areas (updrafts) in thunderstorms.  The relative minimums in CC, displaying in a ring in the right image, depict different hydrometeor types (liquid and ice), indicating that frozen particles are melting into water.  Different target types being lofted also provide a good clue for where updrafts are located, such as along the leading edge of a line of showers and thunderstorms in this example.
 
 Specific differential phase can also contribute in determining the position of the melting layer and updrafts.  Higher KDP values in the melting layer show a greater concentration of liquid water content, while the same is true in areas of heavy rainfall.
 
Training and Additional Information
 
Dual-Polarization Training for NWS Partners (includes meteorologists and non-meteorologists)
National Severe Storms Laboratory Dual-Polarization Page

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