Dual-Pol Upgrade

The exciting dual-polarization radar upgrade to the KEWX WSR-88D is scheduled for installation from March 19 through April 1, 2012! This upgrade will incorporate a new technology called dual-polarization, or dual-pol, that is part of the NWS vision to build a weather-ready nation to better protect lives and livelihoods.  This new technology will result in 14 new radar products that will enable us to continue providing our suite of high quality products and services to the citizens of South Central Texas.  This new technology and data primarily will help forecasters identify the type of precipitation that is falling as well as improve rainfall estimates.

We strongly encourage all users of these new products to complete a series of online training modules that were recorded by the Warning Decision Training Branch (WDTB).  Modules are available for non-NWS meteorologists and non-meteorologists through this website.

What is Dual-Pol?

The current doppler radars transmit and receive pulses of radio waves in a horizontal orientation.  As a result, the radar only measures the horizontal dimensions of targets (e.g. cloud and precipitation droplets).  Dual-polarimetric radar transmits and receives pulses in both a horizontal and vertical orientation.  Therefore, the radar measures both the horizontal and vertical dimensions of targets.  Since the radar receives energy from horizontal and vertical pulses, we can obtain better estimates of the size, shape, and variety of targets.  It is expected that this will result in significant improvements in the estimation of precipitation rates, the ability to discriminate between precipitation types (e.g. hail vs. rain), and the identification of non-meteorological returns.

 Current NWS doppler radar
 Dual-pol radar
Current NWS doppler radar Dual-polarimetric radar

Benefits of Dual-Pol
  • Improved accuracy of precipitation estimates, leading to better flash flood detection
  • Ability to discern between heavy rain, hail, snow, and sleet
  • Improved detection of non-meteorological echoes (e.g. ground clutter, chaff, anomalous propagation, birds, and tornado debris)
  • Detection of aircraft icing conditions
  • Identification of the melting layer (e.g. bright band)

Dual-Pol will not improve tornado lead times or be able to provide exact precipitation type on the ground.

Dual-Pol Products & Applications
The base 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 (HCA) product, and eight new precipitation products.  Hover your mouse over the labels below to see examples of the three new dual-pol base products and a derived product called Hydrometeor Classification Algorithm (HCA).  Images courtesy of the Warning Decision Training Branch.

Differential Reflectivity

APPLICATIONS
Using differential reflectivity to identify a hail core
Using correlation coefficient to identify the melting layer and thunderstorm updrafts
Using specific differential phase to identify the melting layer and thunderstorm updrafts
Images courtesy of WDTB

Training & Additional Information

 


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