High technology meets the High Plains in STEPS-2000

May 03, 2000

Those tapered, bell-shaped thunderstorms that grace so many calendars and posters aren't just photogenic, they're a scientific mystery. Photographers love these so-called low-precipitation (LP) supercells because of their spectacular cloud formations and sparse rainfall. Yet researchers have generally ignored them: they seldom produce tornadoes or flooding, and they tend to occur across the High Plains instead of over more densely populated areas.

Scientists are now realizing that the unsung LP storm may hold a key to understanding the microphysics and electrification of other kinds of thunderstorms. That's why a group of researchers will set up shop in northwest Kansas and eastern Colorado for the Severe Thunderstorm Electrification and Precipitation Study (STEPS), funded in part by the National Science Foundation (NSF). Based in Goodland, Kansas, STEPS-2000 will take place between May 22 and July 15. Involved organizations include the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. NSF is NCAR's primary sponsor. NSF will support a STEPS radar system operated by Colorado State University and an airplane used for microphysical and electrical measurements in thunderstorms, operated by the South Dakota School of Mines and Technology, serving as national facilities for the study.

"This is our first opportunity to bring together several new techniques for observing the electrical properties of storms and the rain and hail they produce," says Rod Rogers, program officer in NSF's division of atmospheric sciences, which funds STEPS-2000. "We are expecting a greatly improved understanding of the relationships between thunderstorm electrification and precipitation production -- and maybe some surprises."

STEPS-2000 will be the largest research effort to date focused on lightning. Data from a national network that tracks the location of cloud-to-ground strikes has hinted at intriguing evolutions in lightning behavior over the course of a storm. The STEPS-2000 study area, along the semipermanent dry line that marks the west edge of Tornado Alley, has one of the nation's highest frequencies of lightning flashes. If STEPS-2000 can follow a storm as it produces a tornado, the link between a storm's electrical behavior and microphysics should become more clear, say atmospheric scientists.

"We're particularly interested in lightning-free holes in supercells," says William Rison, an New Mexico Institute of Mining and Technology (NMIMT) electrical engineer. NMIMT is also involved in STEPS-2000. A system developed by researchers at NMIMT tracked two supercell storms that each had a lightning-free circle, roughly five kilometers wide, within a doughnut-like ring of lightning. One storm produced a tornado in the vicinity of the lightning-free hole. "The hole was almost certainly associated with a very strong updraft in the storm," notes Paul Krehbiel and NMIMT colleagues. At the crown of the updrafts (15-20 kilometers high) in both storms, a separate concentration of lightning was found--to the surprise of researchers.

NCAR scientists Morris Weisman and Charles Knight are especially interested in how embryonic storms become LPs instead of taking a different route. "In the back of everybody's mind, this has been a continuing mystery," said Weisman. Right now, he said, "The distinction between HP [high-precipitation] and LP storms is largely a visible one. Very often an LP will look weak on radar, but if you're watching it in person you see a tremendous updraft."

Another basic question is why the LP storms don't produce much rain. They may contain as much water vapor as their wetter counterparts, but they are far less efficient at producing precipitation. Scientists also don't know how these storms evolve into larger storm systems later on.

Other agencies and institutions involved in STEPS-2000 include the National Weather Service, NOAA's National Severe Storms Laboratory, the University of Oklahoma, and FMA Research, Inc.
-end-
Program contact: Rod Rogers
703-306-1524
rrogers@nsf.gov

NSF is an independent federal agency which supports fundamental research and education across all fields of science and engineering, with an annual budget of about $4 billion. NSF funds reach all 50 states, through grants to about 1,600 universities and institutions nationwide. Each year, NSF receives about 30,000 competitive requests for funding, and makes about 10,000 new funding awards.

For instant information about NSF, sign up for the Custom News Service. From the toolbar on NSF's home page, (http://www.nsf.gov), sign up to receive electronic versions of NSF news, studies, publications and reports. Follow the simple sign-on procedures that guide you to your choices. Also see NSF news products at: http://www.nsf.gov:80/od/lpa/start.htm, http://www.eurekalert.org/, and http://www.newswise.com

National Science Foundation

Related Precipitation Articles from Brightsurf:

Convection-permitting modelling improves simulated precipitation over the Tibetan Plateau
A China-UK research team explains the possible reasons for excessive precipitation over the TP in the mesoscale convection-parameterized models.

Spread of monsoon circulation changes explains uncertainty in global land monsoon precipitation projection
A new study emphasizes the importance of reliable prediction of circulation changes, to ensure that future projections of global land monsoon are suitable for use by policy makers.

GMMIP simulations on global monsoon interannual variability show higher skill than historical simulations
GMMIP simulations on global monsoon interannual variability show higher skill than historical simulations.

The spatial consistency of summer rainfall variability between the Mongolian Plateau and North China
The regional differences and similarities of precipitation variability are hotspots in climate change research.

Scientists find key factors impacting sideswiping tropical cyclone precipitation
Scientists find that the distribution of sideswiping tropical cyclones precipitation(STP) includes extreme STP events that appear not only over the island and coastal areas, but also over inland areas

Rainy season tends to begin earlier in Northern Central Asia
The researchers found robust increase of annual mean precipitation at the end of the 21st century under all modelling scenarios over northern central Asia.

Using cloud-precipitation relationship to estimate cloud water path of mature tropical cyclones
Scientists find the cloud water path of mature tropical cyclones can be estimated by a notable sigmoid function of near-surface rain rate.

Precipitation will be essential for plants to counteract global warming
A new Columbia Engineering study shows that increased water stress--higher frequency of drought due to higher temperatures, is going to constrain the phenological cycle: in effect, by shutting down photosynthesis, it will generate a lower carbon uptake at the end of the season, thus contributing to increased global warming.

Fall precipitation predicts abundance of curly top disease and guides weed management
Transmitted by an insect known as the beet leafhopper, curly top disease is a viral disease affecting many crops, including melons, peppers, sugar beets, and tomatoes.

Study confirms climate change impacted Hurricane Florence's precipitation and size
A new modeling framework showed that Hurricane Florence produced more extreme rainfall and was spatially larger due to human-induced climate change.

Read More: Precipitation News and Precipitation Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.