Dual Pol KNQA

National Weather Service - NWS Memphis/Millington WSR-88D Upgraded to Dual Polarization

Picture of WSR-88D Radome

The Doppler radar in Millington (KNQA) used by the National Weather Service Forecast office in Memphis, Tennessee, was the first radar in the Mid-South to have Dual-Polarization technology used for weather detection, it was updated in December 2011. All other NWS radars across the country are using Dual-Polarization, upgrade was completed in April 2013.

Dual Polarization (or "dual-pol") technology added an additional 14 products to the suite of data already available to NWS forecasters. These tools will assist forecasters in the warning and forecast process.

Why upgrade to Dual Polarization Radar?

By comparing the power and timing of energy returned to the radar from both horizontal and vertical pulses, we can glean information such as the size, shape, and composition of precipitation particles.

What are the Potential Benefits of Dual-Pol?

Better estimation of total precipitation
Better estimation of the size distribution of hydrometeors
Improved ability to identify areas of heavy rainfall (flash flooding potential)
Improved detection and mitigation of non-weather echoes
Easier identification of the melting layer (helpful for identifying snow levels in higher terrain)
Ability to classify precipitation type
New severe thunderstorm signatures

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

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

Horizontal Polarization Graph

Vertical Polarization

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

Vertical Polarization Graph

Current NWS Doppler Radar (horizontally-polarized only)

Current Doppler radar capability transmits and receives only horizontally polarized radio wave pulses. Therefore, they measure only the horizontal dimension of cloud and precipitation particles.

Non-Polarized Radar Picture

"Dual Polarized" Radar

New dual-pol capability will allow the transmit and receipt of both horizontally and vertically polarized radio wave pulses. Therefore, they measure both the horizontal and vertical dimension of cloud and precipitation particles.

Dual Pol Radar Picture

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