“It could pay for itself in accuracy,” he said. According to Schlatter, this study helped build the business case for upgrading 88Ds to incorporate dual polarization technology. After observing a wide variety of weather activity for over a year - tropical rain distributions, supercells, and winter precipitation - it became clear that dual-pol would significantly improve rainfall estimation. “We were pretty sure, even then, that dual-pol was going to be a thing nationwide, even though it was still eight years away.”Īround the same time, the Oklahoma Mesonet and the Agricultural Research Service’s (ARS) Micronet, both prominent environmental monitoring networks, began comparing high density rainfall observations to a dual-pol research radar in central Oklahoma. “They saw the writing on the wall,” Schlatter said. Years later, in 2003, he was hired by the Warning Decision Training Branch (now Division), in part for his expertise interpreting dual-pol radar data. As a result, Schlatter was able to further research regarding specific sizes of raindrops and hail, something that couldn’t be done using a NEXRAD system. In this position, he compared the radar data with images taken of precipitation by aircraft to verify dual-pol radar signatures of rain, graupel, and hail. In 1999, Schlatter was working with a dual-pol radar system at Colorado State University (CSU).
Ideally, meteorologists thought these improved systems could be used to determine the average size of raindrops, thus aiding in the estimation of precipitation rates. In testing the dual polarization technology repeatedly, the NSSL, NCAR, and multiple universities perfected the technology enough to start studying it with a more focused purpose: rainfall estimates. On the whole, the addition of the vertically polarized channel on a dual-pol radar offered meteorologists more in-depth depictions of atmospheric conditions. This remarkable technology proved to have many advantages over the NEXRAD models: improved accuracy of precipitation estimates, leading to better flash flood detection the ability to fully discern between rain, snow, sleet, and hail the improved detection of non-weather echoes like birds and lofted tornado debris and the identification of the melting layer, the atmospheric level at which snow melts into rain. As a result, returned energy on the dual-polarization systems provide more in-depth information, supplying forecasters with better estimates of size, shape, total water content, precipitation type, and overall severity of incoming weather. Dual-polarization radar actually sends and receives pulses in both horizontal and vertical orientation (polarization), while NEXRADs only utilized horizontal polarized pulses. One key difference between NEXRAD systems and dual-polarization radar systems is the transmitter.
As the 88Ds became the national standard, the National Severe Storms Laboratory (NSSL), the National Center for Atmospheric Research (NCAR), and several universities across the country continued researching and working with dual polarization radar technology, in attempts to test the full extent of its capabilities. Although this exciting technology proved to be a huge improvement upon old models, the work was far from over. The NEXRAD radar systems, comprising a network of 159 units across the country, were deployed beginning in 1992, with the last installation occurring in the mid-1990s. Referred to as WSR-88Ds in the technical world, these systems offered storm detection and evolution in never-before-seen detail, providing the ability for improved severe weather warnings. Prior to the development of dual polarization radar, the field took a massive step in technological development with the creation of Next-Generation Radars (NEXRADs).
Paul Schlatter, Science and Operations Officer at the National Weather Service Weather Forecast Office in Boulder, Colorado, is one of the agency’s leading experts on dual polarization so much so that he has earned the moniker “Dual Paul.” Schlatter sat down recently with the NWS Heritage Projects Team to explain the technology and its history. One of the more recent innovations for this stalwart system was the addition of dual polarization or dual-pol. It’s come a long way in the decades since, especially since the installation of the network of NEXRAD Doppler radars in the 1990s. The technology’s honorable beginnings to help identify enemy aircraft during World War II helped propel Allied countries to a victory, and led to its use in weather forecasting. NEXRAD Radar is one of the National Weather Service’s observation staples.