25 August 2011

Dual-Polarization Radar Training and Upgrades

Over the next year the WSR-88D's we all know and love are going to be changing! The concept has been in the works for the last several years. Only recently has it started to be implemented into service. Chicago is going to undergo the upgrade from Oct 17th to 30th. (Let's hope we don't get another major severe weather outbreak in that time frame; Oct 24, 2001-Oct 18th, 2007-Oct 26th, 2010.) The benefits of this upgrade are countless. As described below from the NWS Chicago....

"Conventional Doppler radars transmit bursts of radio waves, called pulses, in a single, horizontal orientation, or polarization. The pulses bounce off meteorological (i.e. clouds, snow, ice pellets, hail and rain drops) and non-meteorological (i.e. birds, insects, ground clutter, including wind farms etc.) particles in the atmosphere, and are reflected back to and received by the radar dish. After computer processing, the returned signals are converted into usable data regarding the horizontal properties of the particles encountered, including their dimensions and direction and speed of movement. For instance, the distance from the radar to the target is calculated from the amount of time that lapses from the initiation of the pulse, to the detection of the return signal. The radar reflectivity you see on a radar image is actually the “reflected” pulse energy that is received by the radar.

Dual-polarization, or Polarimetric, radars transmit and receive both horizontally and vertically oriented radio wave pulses, typically done by alternating between horizontal and vertical polarization with each pulse. This therefore allows the radar to collect data with information on the horizontal and vertical properties of the targets. Being able to analyze targets in this manner is expected to result in significant improvements in the estimation of precipitation rates, the ability to discriminate different precipitation types (i.e. rain vs. hail, mixed precipitation types in winter storms), and the identification of non-meteorological returns. As an added example, for aviation concerns, with polarimetric radar, forecasters will be able to better discern areas of icing and other hazards such as birds. All these improvements will aid forecasters in the warning decision process, helping the public make better decisions about their safety and protecting their property."

So in the end this is a major upgrade that is most welcome. A lot of people are afraid of change, but this and "warn on forecast" are two of the more acceptable ones.

The basic radar products that have been available to users are Z, reflectivity (base and composite), V, mean radial velocity (base and storm relative), and SW, spectrum width. Three new products that will become available after the upgrade are ZDR, differential Reflectivity, CC, correlation coefficient, and KDP, specific differential phase. Below is an example of Differential Reflectivity on the left, versus reflectivity on the right. The area circled on both images is a hail core in a thunderstorm, demonstrating how Differential Reflectivity can allow for better discrimination of hail from just heavy rainfall. Along with the three base products above, included among three new derived products will be Quantitative Precipitation Estimation (QPE), which will allow for the estimation of instantaneous rainfall rate. Currently, only 1-hour radar-based rainfall rate estimations are available.

For more information on the specific NWS LOT upgrade click HERE 

Meteorologists, non-meteorologists, emergency management, and civilians alike are able to access this radar and can learn more about it by following this link and going through the training modules. I know there are a lot of people out there that like to utilize radar and like to see what is coming at them. Here is a perfect way to train yourself to use this brand new upgrade right off the bat. 


NSSL conducted the Joint Polarization Experiment (JPOLE) in 2002-2003 to demonstrate the operational capabilities of the polarimetric KOUN. During JPOLE, data were delivered in "real-time" to the NWS and other users. NSSL scientists aided in the data interpretation. JPOLE proved that significant improvements in rainfall estimationprecipitation classificationdata quality and weather hazard detection were possible using polarized radar. The impacts of polarimetric radar could be as significant as the nationwide upgrade to Doppler radar in the 1980's, providing measurable benefits to...
  • Polarimetric radar can significantly improve the accuracy of the estimates of amounts of precipitation
  • Polarimetric radar can tell the difference between very heavy rain and hail, which will improve flash flood watches and warnings
  • Polarimetric radar can identify types of precipitation in winter weather forecasts, improving forecasts of liquid water equivalent or snow depth
  • Polarimetric radar data is more accurate than conventional radar, saving the forecasters the step of having to verify radar data
  • Increased confidence in polarimetric radar data can contribute to increased lead time in flash flood and winter weather hazard warnings.
  • Polarimetric radar provides critical rainfall estimation information for stream flow forecasts and river flooding
  • Polarimetric radar could be useful in water management
Aviation users:
  • Polarimetric radar detects aviation hazards such as birds
  • Polarimetric radar can detect aircraft icing conditions
  • Polarimetric radar has the potential to save the public $690,000,000 annually by improving precipitation estimation
  • Polarimetric radar can improve forecasts and warnings and reduce the impact of hazardous weather on our national transportation
  • Polarimetric radar better equips forecasters to issue accurate warnings and in turn helps the public make wiser decisions about our safety


  • Dual-Polarization Technology OverviewClick here to download the Dual-Polarization Technology Overview Presentation for Local Viewing

  • Best Uses for the Hydrometeor Classification ProductClick here to download the Hydrometeor Classification Presentation for Local Viewing

  • Best Uses for the Dual-Polarization Estimated Rainfall Amount ProductsClick here to download the Estimated Rainfall Amount Presentation for Local Viewing

  • The information gathered above is not ALL my own.. The modules/descriptions were gathered from the official Dual-pol pages which I have linked. With this information being passed along I hope you (the general public) will educate and become informed with what is going on with your local National Weather Service Forecast Offices. Give it a try!

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