So what exactly is dual-polarization and how does it differ from the conventional Doppler radar that we’ve used for years now? All weather radars, including Doppler, send out pulses of energy into the atmosphere in order to detect precipitation. When a pulse of energy hits a raindrop or a snowflake, for example, some of that energy is “reflected” back to the radar, which can then be mapped through computer software for display to meteorologists and general public. If you've seen or heard the term “radar reflectivity” before on TV or the internet, this is where that comes from! The radar is simply measuring the amount of reflected energy it’s received back. The more reflected energy that’s received back, in general, the heavier the precipitation that is being detected. This is how we can differentiate between areas of lighter and heavier precipitation.
Up until recently, weather radars have sent out these pulses of energy oriented in only one direction - horizontally (see animation below). While this is sufficient for the general detection and overall intensity of precipitation, characteristics of the precipitation droplets, such as their size, shape, dimensions, and composition, can not be determined using only radar pulses oriented horizontally. In meteorology, knowing these details can be crucial in identifying whether precipitation is in the form of rain, snow, or even hail.
- Better estimation of overall precipitation amounts
- Improved detection of areas of heavy rainfall and flooding potential, improving the warning process
- Improved detection and mitigation of non-weather echoes (removal of false returns such as ground clutter from the radar display)
- Ability to classify possible precipitation types (which will improve even more with the subsequent software updates following the initial deployment of dual polarization)
- New severe thunderstorm signatures, including better detection of hail and even tornado debris, aiding in the warning process
During this time, data from the NWS radar in Millington, which also powers MemphisWeather.Net’s StormView Radar, will not be available. Surrounding regional radars should remain online to help monitor the weather conditions in the Memphis metro and Mid-South area, and MWN provides links to those surrounding radar sites in the “Radar/Satellite” menu on our website. We will also provide links as needed on our Facebook and Twitter feeds during the upgrade.
If you want more information on the impending radar upgrade to dual polarization and other general information about it, visit the links below.
- Latest from the NWS in Memphis on the Dual Polarization Upgrade
- Frequently Asked Questions about Dual Polarization, from the National Severe Storms Laboratory
- Basic Training on Dual Polarization for Non-Meteorologists, from the NWS Warning Decision Training Branch
For weather information for Memphis and the Mid-South, where and when you need it, visit MemphisWeather.net on the web, m.memphisweather.net on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.