Hot Items 2004NSSL Scientist Featured in NOVA Program
An episode of the PBS TV series “NOVA” airing Tuesday will feature scientists' efforts to understand nature’s most violent tornadoes, from daredevil storm chasing in tornado alley to simulating severe weather, including the work of Louis Wicker, a research meteorologist at the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory in Norman, Okla.
The show will feature data-driven tornado visualizations created by a team that included Wicker and the computational resources and visualization expertise of the National Center for Supercomputing Applications (NCSA) and the Department of Atmospheric Sciences at the University of Illinois at Urbana-Champaign.
"Hunt for the Supertwister," produced by Tom Lucas of TL Productions, was created in High Definition TV format (HDTV) and will air at 8 p.m. Eastern Standard Time March 30 on PBS stations across the country.
The program also features Steve Weiss, science operations officer at the NOAA Storm Prediction Center, researchers Howard Bluestein and Kelvin Droegemeier from the University of Oklahoma, and Josh Wurman from the Center for Severe Weather Research.
In a typical year, 1,200 tornadoes cause 70 fatalities and 1,500 injuries nationwide. Most of the damage, deaths, and injury are due to a very small percentage of these tornadoes, the powerful so-called "supertwisters."
Ideally, forecasters would be able to provide enough advance warning that people could protect themselves from these killer storms, but accurately predicting when and where tornadoes will strike is a feat that continues to elude forecasters. "Hunt for the Supertwister" details scientists' efforts, both in the field and in the lab, to understand the most violent tornadoes.
Scientists know that the strongest tornadoes are generated by a particular type of rotating thunderstorm called a supercell. The constantly swirling winds of a supercell can produce tornadoes, but not all supercells lead to tornadoes, and not all tornadoes become supertwisters. Why some storms spawn tornadoes while others don't—and why some tornadoes become extraordinarily strong supertwisters—is not yet well understood.
In an effort to pinpoint what triggers tornadoes, researchers create computer simulations of evolving storms. Just as physicians use X-rays and CAT scans to diagnose disease, storm researchers use simulations and visualization to analyze tornado formation.
"The big problem in storm science is that with the instrumentation we have we can't sense all the things that we need to know," explains Wicker. "From the field, we can't figure out completely what's going on, but we think the computer model is a reasonable approximation of what's going on, and with the model we can capture the entire story."
Wicker developed a model called NCOMMAS (NSSL Collaborative Model for Multiscale Atmospheric Simulation) to computationally simulate thunderstorms and their associated tornadoes. NCOMMAS is based upon an earlier model developed by Robert Wilhelmson, NCSA research scientist and University of Illinois professor of atmospheric sciences.
The simulation begins with data describing the pre-tornado weather conditions—wind speed, atmospheric pressure, humidity, etc. From these initial variables, a virtual storm is born.
The data used by Wicker is based on an F4 storm that devastated Manchester, South Dakota, on June 24, 2003. The resulting simulation takes shape with uncanny similarity to the real thing. Lucas and his crew caught the Manchester supertwister on HDTV video, so the real and simulated storms will be juxtaposed in the NOVA special.
Starting with the recorded pre-storm conditions near Manchester, the simulation followed the erupting thunderstorm and resulting powerful tornado as it evolved in a 100 x 100 x 25 km domain. The calculations were performed on NCSA's IBM p690 computing cluster in November 2003. To simulate about two and a half hours of "cloud time" required the use of 16 processors for 10 days.
The simulation produced 650 billion bytes of data. These snapshots of the evolving storm consist of wind temperature, humidity, and precipitation data every few seconds for more than three hours.
NCSA's visualization team translated the data into a dynamic, high-definition animated visualization of the tornado's birth and growth. In the final visualization as it will be seen by NOVA viewers, a swirling blue-gray cape of isosurfaces represents the body of the tornado, while swaying cones tilt to show wind speed and direction at ground level. Balls and tubes of varying colors indicate the tornado's pressure and rotation rate.
Wicker and others are using the visualization to gain new insights into tornadoes, how and when they form, and why they become strong.
“The simulation is only the beginning,” Wicker said. “Trying to understand it is the hard work.”
The National Severe Storms Laboratory leads the way in investigations of all aspects of severe and hazardous weather. Established in 1964, NSSL is part of NOAA Research and the only federally-supported laboratory focused on severe weather. The Lab’s scientists and staff explore new ways to improve understanding of the causes of severe weather and ways to use weather information to assist National Weather Service forecasters, as well as federal, university and private sector partners.
Now in its thirty-first year of broadcasting, NOVA is produced for PBS by the WGBH Science Unit. The director of the WGBH Science Unit and senior executive producer of NOVA is Paula S. Apsell. NOVA is closed captioned for deaf and hard-of-hearing viewers, and described for people who are blind or visually impaired by the Media Access Group at WGBH. The descriptive narration is available on the SAP channel of stereo TVs and VCRs. Major funding for NOVA is provided by the Park Foundation, Sprint, and Microsoft. Additional funding is provided by the Corporation for Public Broadcasting and public television viewers.
http://www.pbs.org/nova/tornado
3/26/2004