RADAR DEVELOPMENT HIGHLIGHT OF NATIONAL SEVERE STORMS LABORATORY’S
FIRST 40 YEARS
29, 2004 — Who would have imagined that radar technology designed
to detect and locate hostile aircraft and missiles in WWII would serve
as the basis for today’s advanced weather
radar systems. At that time, storms were a nuisance that obscured
valuable data. Later, however, users realized the potential benefits of
radar for weather detection. Now, the NOAA
National Weather Service relies daily on radar to detect, locate and
measure precipitation inside clouds. In fact, today's radars are so advanced
they can even identify types of precipitation, detect important weather
features that make a storm severe, and track and predict the motion of
National Severe Storms Laboratory
Much of the credit for modern weather radar systems should be given to
the NOAA National Severe Storms Laboratory
in Norman, Okla., which celebrated its 40th
anniversary in mid-October. “We want to take this time to savor
our accomplishments over these past 40 years and look optimistically toward
the future,” said James
F. Kimpel, NSSL director.
Established in 1964, the NOAA NSSL leads the way in investigating all
aspects of severe and hazardous weather. NSSL is part of NOAA
Research and is the only federally supported laboratory focused on
severe weather. NSSL’s scientists and staff explore new ways to
improve understanding of the causes of severe weather and how to use weather
information to assist NOAA National Weather Service forecasters, as well
as federal, university and private sector partners.
very foundation of today’s NSSL lies in weather
radar research and development that began before the lab’s origin
in 1964. Two years earlier, the National Severe Storms Project had established
its Weather Radar Laboratory in Norman, Okla. This facility became a major
component of the new NSSL. Part of NSSL’s initial role was to maximize
the use of the original WSR-57 surveillance radars for the U.S. Weather
Bureau (now the NOAA National Weather Service).
For the first few years, NSSL collected data on Oklahoma spring storms
using the WSR-57. The WSR-57 weather radar worked by sending out short
bursts of energy in a beam that came from a slowly rotating antenna. When
the beam hit particles the size of rain, snow or hail some of the energy
was reflected back to the antenna. If the particle was large, more energy
bounced back. NSSL engineers made it possible to see the strength of the
returned energy by creating a contoured black and white display. The Weather
Bureau and most other radar users quickly adopted this technology because
it provided more detailed information about storm strength.
In 1964, scientists were working to acquire additional radar technology.
A 3-cm wavelength research Doppler
radar was added to NSSL’s list of assets — a move that
would revolutionize weather observation. This new radar allowed scientists
to delve into and measure motion inside the storm for the very first time
— providing valuable clues into the development of severe weather.
A change in frequency
occurred when a radar signal was reflected from a moving target, such
as a cluster of raindrops – similar to the shift in frequency experienced
with a passing sound (e.g., when a train blowing its whistle passes by).
When they measured this shift in frequency, scientists could tell if particles
were moving towards or away from the radar. It is this ability to discern
internal air circulation that makes Doppler
radar such a powerful weather-monitoring tool.
and engineers soon discovered the 3-cm radar was not powerful enough for
a large-scale storm surveillance network, and NSSL embarked on a program
to develop a much stronger 10-cm Doppler
radar. In 1969, NSSL was able to obtain and upgrade a surplus 10-cm
radar that had been used by the U.S. Air Force.
Doppler radar in Norman became operational during the 1971 spring tornado
season. Data were collected on magnetic tapes and processed on a NASA
computer weeks or even months later because there was no real-time capability.
made many significant discoveries using these data, but one of the most
important was the discovery of the tornadic
vortex signature. When a circulation begins to form, its winds blow
raindrops in a signature pattern on the radar screen. In May of 1973,
a devastating tornado tore through Union
City, Okla., a town just west of Oklahoma City. For the first time,
Doppler radar and storm intercept teams documented the entire life cycle
of the tornado. In reviewing the data, researchers discovered that a small-scale
Doppler velocity circulation appeared aloft even before the tornado descended
to the ground — a feature that would allow forecasters to better
warn the public of the impending danger.
research on thunderstorms led to the Joint Doppler Operational Project,
which tested the warning potential of the Doppler radar. JDOP conclusively
showed that Doppler radar had the potential to assist in issuing more
accurate warnings, and more importantly, warnings with enough lead time
for the public to find safe shelter.
Advances: Dual Doppler And Pulse-Pair Processing
In 1974, a second 10-cm Doppler radar was constructed 26 miles northwest
of the Norman Doppler radar. Known as the Cimarron Doppler radar (because
of its location), it provided “dual-Doppler” capabilities.
With both radars, scientists could see the same storm from two different
perspectives, and pioneered studies on the structure of tornadic storms
at different levels. Other advances included color displays and the development
of pulse-pair processing, an efficient computational algorithm that uses
pairs of pulses to compute Doppler velocity and display them in real-time
(instead of days later).
capabilities were added to the Cimarron Doppler radar in time for the
1985 spring storm season. Scientists had learned that when pulses were
vertically and horizontally the return signal provided a clearer indication
of cloud and precipitation particle size, shape and ice density —
they could determine if the targets were round like hailstones or somewhat
flattened like raindrops.
This information had great potential to improve severe weather warnings.
NSSL’s research helped convince the NWS that Doppler radar was a
crucial forecasting tool. Beginning in the mid-1980’s, NSSL worked
to make Doppler radar data useful for NOAA NWS forecasters in preparation
for a national deployment of the radars. During field programs like DopLight,
Doppler radar and lightning data were provided in real-time to both the
Oklahoma City Weather Forecast Office and local TV media. Various algorithms
were developed to detect and notify forecasters of hail, severe thunderstorms,
tornadic circulations, downbursts and gust fronts (the leading edge of
rain-cooled air), and track the movement of storms. These algorithms were
later combined with a color display system and became known as the Warning
Decision Support System.
on this work, and JDOP,
the national network of 150 WSR-88D (Weather Surveillance Radar- 1988
Doppler) radars, or NEXRAD (short
for NEXt generation RADar)
were deployed in the early to mid-1990’s, jointly developed and
operated by the NOAA NWS, Department of Defense and Federal Aviation Administration
throughout the United States and selected overseas locations. The NEXRAD
project replaced the older WSR-57 radars and now provides comprehensive
radar coverage of the United States.
NSSL received a Gold
Medal from the Department of Commerce for work leading up to and their
support of the national NEXRAD deployment. All the while many other scientists
worked to find valuable clues in the data that were being produced.
Advances In Doppler/NEXRAD Technology
During the 1990’s, NSSL designed and implemented software for NEXRAD’s
Open Radar Product Generator.
The ORPG processes Doppler radar data and generates products for use by
NEXRAD customers. Other NSSL teams worked on NEXRAD’s Open
Radar Data Acquisition Unit to improve how basic data is acquired
and to allow for future enhancements as needs of the industry change.
NSSL’s 20 years of polarimetric weather radar research were rewarded
in the fall of 2003 following JPOLE, the
Joint Polarization Experiment.
JPOLE proved the engineering design and quality of data provided by a
polarimetric radar would benefit operational users. The NOAA NWS recently
approved taking the first steps to upgrade
all the WSR-88D Doppler radars in the NEXRAD network with polarimetric
capabilities will complement information the Doppler radars already provide
on wind, precipitation and storm motion. Another important discovery was
that dual-polarization improved rainfall estimates with the 25 WSR-88D
radars in the western United States where radar beams were blocked by
Radar Acquisition Field Test or “CRAFT,” was another milestone
as researchers from NSSL, the University of Oklahoma, the NWS Radar Operations
Center, the University Corporation for Atmospheric Research-Unidata, Internet-2,
and the National Climatic Data Center were able to prove that access to
high-resolution data from multiple radars was technically possible and
economically viable. As a result, high-resolution radar data from the
national network of NEXRAD radars will soon be available over the Internet
in real-time to government, university and private sector users.
NSSL is also
heading a project to seamlessly mosaic all NWS and Department of Defense
WSR-88D radars across the United States to provide the first high-resolution
depiction of storms and quantitative precipitation estimates from coast
to coast in real-time.
Doppler Research Radar
Moving radar technology in a different direction, NSSL (in partnership
with the University of Oklahoma, Texas A&M and Texas Tech) developed
and are using Shared Mobile
Atmospheric Research and Teaching Radars (also known as “SMART-Radars”).
SMART-Radars are mobile Doppler radars that can be placed in position
as a storm is developing rather waiting for storms to occur within range
of stationary radar systems. Two SMART-R’s have already been used
to study tornadoes, hurricanes
and other weather phenomena across the country.
NSSL (with the help of its partners, the Navy, Federal Aviation Administration,
University of Oklahoma, Oklahoma State Board of Regents, National Weather
Service, Lockheed Martin and Basic Commerce Industries) is now leading
radar technology into the future with a facility dedicated to phased
array radar research and testing in Norman, Okla. Phased
array radar uses electronically controlled multiple beams and frequencies
on a flat plate antenna (instead of a parabolic or bowl-shaped antenna),
which reduces the scan time of weather systems from five to six minutes
for NEXRAD radar to only one minute. Phased array radar can also scan
the atmosphere at lower levels more effectively and has the capability
to quickly re-scan areas with the most severe weather — potentially
increasing forecasters' warning lead times. Data gathered
from phased array radar will also be used to initialize computer models
and improve forecasts. It is expected to take 10-15 years to move from
research and development to technology transfer and deployment.
and creativity spanning 40 years, NSSL engineers and scientists have taken
technology to the edge. From the original WSR-57 research project to Doppler
radar, NEXRAD, and now polarized and phased array radars, NSSL’s
radar research has truly changed the face of weather.
NATIONAL SEVERE STORMS LABORATORY CELEBRATES 40 YEARS
Radar Technology Can Increase Tornado Warning Lead Times
Archive of Stories
Array Radar Backgrounder
of NEXRAD Products
UNVEILS NEW EXPERIMENTAL RADAR TECHNOLOGY
EXPERTISE FOR DEVELOPMENT OF NEW RADAR NETWORK
NATIONAL SEVERE STORMS LABORATORY INVESTIGATES ALL ASPECTS OF SEVERE AND
IN NOAA TORNADO RESEARCH AND FORECASTING TECHNOLOGIES OVER THE LAST CENTURY
RADAR CAPTURES IMAGES OF HURRICANE LILI AT LANDFALL
RESEARCHERS HELP DEVELOP NEW EARLY-WARNING RADAR
DEVELOPING RADAR OF THE FUTURE
NOAA Weather Partners, Norman,
Okla., (405) 366-0451
Article Drafted by Susan Cobb, NSSL