Dual-Polarization Radar Coming to Jacksonville!

An exciting upgrade is coming to the NWS Jacksonville WSR-88D; starting February 13, 2012, the radar will be transformed into a dual-polarization radar!  What does a dual-polarization radar do that the current 88D radar does not?  Instead of the radar transmitting only horizontally pulses of energy to detect atmospheric targets (like raindrops and hailstones), the new dual-polarization radar technology will enable the radar to sample targets both horizontally and vertically.  This second dimension of target information can provide meteorologists better estimates of target type, size, and variety.

While the Jacksonville radar undergoes dual-polarization installation, please note that the KJAX radar will be offline for about two weeks from February 13th through February 26th, and during this time radar data will be unavailable. The Moody Air Force Base 88D (KVAX) is expected to undergo the dual-polarization upgrade in March 2013. When the local radars are unavailable during their dual-polarization upgrades, please use surrounding radars to monitor shower and thunderstorm activity: Tallahassee (KTAE); Robins Air Force Base Jeffersonville (KJGX); Charleston (KCHS); Tampa Bay (KTBW); and Melbourne (KMLB).   

Radar customers are encouraged to get more information regarding dual polarization technology.  Here are several great resources to investigate: 

What is Dual-Polarization?                                                                                   

Dual-Polarization technology transmits pulses of energy into the atmosphere both in the vertical and horizontal directions, and also recieves reflected energy back from atmospheric targerts in both the veritical and horizontal directions. This two-dimensional picture of atmospheric targets will give meteorologists a better understanding of what type of precipitation, if any, is actually out there.  Meteorologists will be able to better discern hail from heavy rainfall, birds from showers, and rain from snow!  

Current 88D radar gives meteorologists an idea of how intense precipitation is and which direction and how fast it is moving. However, the current 88D provides very little information on precipitation type. Dual-polarization technology will provide additional information about the size and shape of a precipitation target, and, with this information, forecasters will have greater confidence to accurately assess weather events including identifying rain, hail, snow and ice pellets.

Traditional vs Dual-Pol Radar Pulse Orientations

Traditional Radar Horizontal Pulse   Dual-Polarization Vertical & Horizontal Pulses









Benefits of Dual-Polarization Radar                                                                      

  • Improve the accuracy of identifying precipitation types.
  • Improve precipitation estimation, which will ultimately improve flash flood warnings and river level forecasts.
  • Identify precipitation types which will ultimately improve winter weather forecasting and hail detection. 
  • Dual-Pol will filter out atmospheric targets like birds, bugs, and bats so forecasters can focus on weather only.
  • Identify airborne tornado debris, which will assist in locating and tracking some tornadoes.
The cumulative benefit of dual-pol radar technology is that it provides forecasters a new suite of products to help them issue more timely and accurrate warnings to help protect life, property and commerce. Check our the next section that details the new dual-polarization radar products, and how they can be used with current 88D radar products to determine precipitation characteristics and more.

Dual-Polarization Products and Applications                                                  

The base 88D radar products that have been available to users are base reflectivity, base velocity, and spectrum width.  Three new base products will be available after the dual-pol upgrade, including differential reflectivity (ZDR), correlation coefficient (CC), and specific differential phase (KDP).  In addition to these three new base products, there will be several dervied products.  These include a melting layer (ML) product, a hydrometeor classification algorithm (HC) product, and new precipitation products. 

Remember, no one radar product can be soley used to determine weather impacts; rather the suite of products, both from the traditional 88D and the new dual-pol products, analyzed over time and space through numerous atmospheric levels will help forecasters assess a variety of possible weather threats.

Dual-Pol Product Definition Applications (click on image to enlarge)
Differential Reflectivity (ZDR) Difference between the horizontal & veritical reflectivity factors (units dBz).  
Correlation Coefficient (CC) Measure of how similarly the horizonal and vertical pulses are behaving in a pulse volume.  
Specific Differential Phase (KDP) The range derivative of the differential phase shift between the horizontal and vertical pulse phases.  
Hydrometeor Classification Algorithm (HC) Determine most likely class of precipitation type.  


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