For release: 03/01/02
Release #: 02-044
NASA study of ‘erratic’ hurricane season offers hope for improved storm prediction, understanding
Data gleaned from studies of the 2001 hurricane season — with its unpredictable series of nontraditional storms — may hold a key to improved hurricane prediction and understanding, say scientists leading NASA’s fourth Convection And Moisture Experiment (CAMEX) study.
“This hurricane season was dramatically different from the season we monitored during Camex-3 in 1998,“ said Robbie Hood, CAMEX mission scientist from NASA’s Marshall Space Flight Center, Huntsville, Ala.
“This year, the storms were erratic, nontraditional and more difficult to predict. In general, they didn’t form or dissipate in traditional timeframes, exhibit the same correlation between wind fields and rainfall, or follow typical patterns, such as having a well-defined eye.”
“This is good news for CAMEX researchers, who now have an entirely new set of data for use in improving hurricane modeling and prediction,” said Hood.
“During the 1998 CAMEX study, we obtained a massive amount of information from classical hurricanes such as Bonnie, Danielle, and Georges," she said. “Those data, combined with information obtained this year, gives us two complimentary data sets. The true value will be in comparing them.”
Based out of the Naval Air Station at Jacksonville, Fla., this year’s hurricane study mission was Aug. 16 through Sept. 24 — traditionally the most active period of the hurricane season. The mission united researchers from 10 universities, five NASA centers and the National Oceanic and Atmospheric Administration (NOAA).
Using aircraft, unpiloted aerial vehicles, satellite observations, ground-based radar and other instruments, the team studied Tropical Storm Chantal in the Caribbean, landfalling Tropical Storm Gabrielle in the Gulf of Mexico, and hurricanes Erin and Humberto as well as Tropical Storm Gabrielle, again, in the Atlantic Ocean.
CAMEX scientist Dr. Ed Zipser of the University of Utah, Salt Lake City, sees great potential for using the 2001 data to compare “model” storms with storms that occur in the real world.
“Theories and numerical models of hurricanes have been very successful in explaining how these storms often reach great intensity,” he said. “However, the inconvenient fact for forecasters and scientists studying these storms is that most real storms fail to reach their potential while most model storms do.”
This year’s data, he believes, will help scientists investigate unconventional storm structures and identify the roles they play in a hurricane’s failure to intensify as expected.
For scientists, a highlight of CAMEX-4 was realizing the goal of flying into the same storm for two or more consecutive days. To accomplish this, they teamed up with participants in the NOAA-sponsored hurricane study, the Hurricanes at Landfall Experiment. Together, CAMEX and NOAA scientists monitored Hurricane Humberto with both NASA and NOAA aircraft for three full days while it intensified — giving researchers added data in understanding how hurricanes form.
“We had three multi-aircraft missions over Hurricane Humberto,” said Gerry Heymsfield of NASA’s Goddard Space Flight Center in Greenbelt, Md. “These were the most comprehensive measurements of the structure of the hurricane ever recorded.”
Another history-making achievement of CAMEX-4 was the successful wind-finding Dropsondes through the eye of two storms — Erin and Humberto — from an unprecedented 65,000 feet (19,800 meters). This was accomplished through Global Positioning System (GPS) Dropsonde experiments, conducted by the Goddard Center and the University of Maryland in Silver Springs. Dropsondes are mobile instruments resembling Pringles potato chip containers. Released from aircraft through special chutes,
Dropsondes descend via parachute, measuring and transmitting data such as wind, temperature, humidity and air pressure.
Another milestone was the first flights of unpiloted aerial vehicles for hurricane research. Managed in conjunction with the University of Colorado at Boulder, the Aerosonde Robotic Aircraft skimmed the ocean surface collecting data on atmospheric temperature, pressure, relative humidity, and winds — data that cannot be obtained by any other method from these very important near-surface altitudes."
Through the ground-based component of CAMEX, known as the Keys Area Microphysics Project (KAMP), scientists for the first time intercepted a land-falling tropical cyclone with a truck-mounted 5-centimeter wavelength, or C-band, Doppler radar — achieving notable success in documenting the landfall of Tropical Storm Gabrielle.
With guidance from NOAA scientists from the Hurricane Research Division, two mobile radars and a microwave profiling system were moved from their original stations in the Florida Keys, and positioned near Venice, Fla., ahead of the storm.
Despite buffeting from winds and torrential rain, the system observed winds slightly below hurricane force. The data acquired through the KAMP study has the potential to help improve precipitation estimates from passive and active microwave instruments — equipment that detects precipitation and surface water by measuring natural microwave emissions from cloud water, cloud ice, rainfall and surface water.
When all CAMEX-4 data are calibrated and archived — a process expected to take about six months — all participating scientists will share the information. “The database resulting from CAMEX-4 will provide riches from which many important advances can be anticipated,” said Zipser.
The study is part of NASA’s Earth Science Enterprise, a long-term research program dedicated to better understanding the total Earth system and the effects of natural and human-induced changes on our global environment.