The Earth’s weather patterns have been much more extreme over the last few years. Massive hurricanes, like Maria which devastated Puerto Rico in 2017, caused a great loss of life and Billions of dollars in damage. The July 2019 European heat wave was linked to 1,500 deaths and saw temperatures never before recorded.
With these extreme weather patterns, the importance of predicting where and when severe weather will hit is of the highest concern. Forecasters have been improving computer models for decades, but without data to feed those models prediction is impossible. Enter phased array Doppler radar.
Advantages of Doppler Radar
We have all observed the Doppler effect when the source of waves, like a freight train, is moving with respect to a stationary observer. As the freight train approaches, the frequency of the sound it produces increases, increasing its pitch.. As the freight train passes, the frequency decreases. This is the result of the Doppler effect, and this effect isn’t limited to just sound: it works with any wave, including electromagnetic waves and radar.
Doppler radar provides a high level of signal quality data as compared to most other radar techniques. Doppler radar is used by a meteorologist to diagnose rainfall as well as provide data on the flow of wind in the atmosphere. It also accurately predicts how severe a thunderstorm will be and delivers a warning very quickly to local residents. It can accurately forecast changes in the wind and the flow of wind and air motion in a storm.
The National Severe Storms Laboratory (NSSL) has a Multi-function Phased Array Radar (MPAR) system which can profile wind currents and perform weather surveillance while tracking aircraft as well.
Research is ongoing, but let’s just take a look at what electronically-steered Phased-Array Radar (PAR) is all about.
The use of Active Electronically-Scanned Arrays (AESA) are the newest phased-array radar antenna technology. Years ago, these types of radar antennas were mechanically steered, dish-shaped antennas, which had a high manufacturing cost, were large in physical size, and the mechanical steering was subject to wear.
The most powerful radar in the world is the WSR-88D. It operates at a transmit power of 750,000 watts. This radar is a mechanically-scanned architecture and the system is a Doppler radar which was introduced in 1988. Doppler effects determine an object’s velocity data from distance. This is done by bouncing of microwave signals off the target and determine how the object’s motion alter the frequency of returned signals.
The National Weather Service is testing different radar schemes to see which system will have the best advantages to help detect weather events and give the earliest warning possible to communities so they could prepare for dangerous weather. The Phased Array Radar Innovative Sensing Experiment (PARISE) is a key part of the Multi-function Phased Array Radar (MPAR) program for the National Weather Service.
PARISE research has tested electronic adaptive scanning of PAR vs. mechanical adaptive scanning in radar systems. They observed a 2014 severe hail and wind event in Oklahoma and found that the PAR system was best at seeing atmospheric events that precede severe hail and wind and seeing downburst precursor signatures up to 12 minutes before a maximum intensity downburst.
Radar technology is quickly advancing with newer, higher resolution electronics technology in a smaller package. Digital electronics and the addition of Artificial Intelligence (AI) is making weather predictions before they actually become a threat to life and property. More exciting technology will be discussed in this forum as we advance with new creativity. Stay tuned.
1 Multi-function Phased Array Radar, MOAA National Severe Storms Laboratory, March 2015
2 Computational Electromagnetic Tools Applied to the Polarimetric Phased Array Antenna, Mirković, D., D.S. Zrnić, 2019, NOAA/NSSL report.
3 Design Challenges of Next-Generation AESA Radar, National Instruments, 2017
4 Everything you ever wanted to know about the NWS WSR-88D, National Weather Service
5 radartutorial.eu, Weather Radar WSR-88D