Dual Polarization Coming To A NWS Radar Near You!

Dual Polarization Coming
To A NWS Radar Near You


Over the next year and a half or so, the National Weather Service's radar network will be retrofitted with new hardware and software in support of dual polarization technology.  The upgrade to a radar takes just under 2 weeks and requires the radar to be taken out of service during that time.  NWS Chicago has already been upgraded.  Our radar here at NWS Milwaukee/Sullivan is scheduled for this technology upgrade April 2-15, 2012.    Four to five teams will be traveling the country upgrading the radar network across the United States.  Here is more information about this important upgrade: 

 

Picture of WSR-88D Radar

Photo Courtesy of Reid Wolcott

 


This much anticipated upgrade is part of the NWS vision to build a Weather-Ready Nation to better protect lives and livelihoods. This exciting upgrade will incorporate a new technology called dual-polarization, or dual-pol. 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 public. This new technology and data will primarily help forecasters identify the type of precipitation that is falling as well as improve rainfall estimates
Why Upgrade to Dual-Pol?
Current NWS 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, such as chaff, ground clutter, and smoke plumes from wildfires that are not uncommonly detected by weather radar systems such as WSR-88D.
Current NWS Doppler Radar
Dual-Pol Radar
The Benefits of Dual-Pol
  • Better estimation of total precipitation amounts
  • Better estimation of the size distribution of hydrometeors (raindrops, snowflakes, hailstones, drizzle)
  • Much improved ability to identify areas of extremely heavy rainfall that are closely linked with flash floods
  • Improved detection and mitigation of non-weather related radar echoes (chaff, smoke plumes, ground clutter)
  • Easier identification of the melting layer (helpful for identifying snow levels in higher terrain)
  • Improved ability to classify precipitation type

The full benefit of dual-pol radar, however, will not be fully realized until NWS forecasters and research meteorologists develop real-time expertise.
What is Polarization?

A radio wave is a set of oscillating electric and magnetic fields, oriented 90 degrees to each other. Polarization of the wave is the direction, or orientation, of the electric field.

Horizontal Polarization
Horizontal Polarization Graph

The electric field is oriented horizontally, along the x-axis (blue). The magnetic field is oriented vertically along the y-axis (white).

Vertical Polarization
Vertical Polarization Graph

The electric field is oriented vertically, along the y-axis (orange). The magnetic field is oriented horizontally along the x-axis (white).
Want to Learn More?


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