NASA's GRIP to Take Unprecedented Look Inside Hurricanes
The spinning, counterclockwise drama plays out across TV screens all summer long. Satellite images show a tropical depression forming off the coast of Africa, and the people at home invariably ask the same question as the forecasters and the scientists: Will it or won't it become a hurricane?
This August and September, NASA is leading an aircraft campaign that will provide a sustained and unprecedented look at the inner workings of hurricane formation and intensification. The Genesis and Rapid Intensification Processes (GRIP) experiment will take place from Aug. 15 to Sept. 30 and employ three NASA aircraft flying over the Gulf of Mexico, Atlantic Ocean and Caribbean Sea to try to answer some of the basic but still lingering questions about how and why hurricanes form and strengthen.
NASA has flown over hurricanes before to gather data on precipitation, winds, convection, temperature and other factors that are known cyclone ingredients. The logistical demands of doing so have only allowed for two to four hours of data collection at a time, a snapshot of a storm that could spin for days. But for the first time, scientists will fly an unmanned drone, outfitted with 3-D radar, a microwave radiometer and other instruments over tropical systems for up to 20 consecutive hours.
NASA's Global Hawk – the same Northrop Grumman-made model as flown by the U.S. Air Force – will fly at up to 65,000 feet and provide the longest continuous observation of tropical cyclone development ever recorded by an aircraft. NASA scientists hope the high quality of this data – the Global Hawk's instruments have the capability to peer through cloud tops and measure the internal structure of a storm – will offer new insights into the fundamental questions of hurricane genesis and intensification.
Along with the Global Hawk, a suite of instruments on NASA's DC-8 and WB-57 planes will capture data on what is happening with winds, temperature, humidity, clouds, ice, lightning, aerosols and other factors inside tropical cyclones as they form and intensify, or as they fizzle and weaken. With the added observations of NASA's spaceborne instruments – particularly the joint U.S.-Japan Tropical Rainfall Measuring Mission satellite and those in the A-Train constellation of satellites satellite – GRIP has been devised to apply NASA's unique capabilities toward addressing some of the shortcomings in hurricane science.
"It has been a lot of hard work to assemble the science team and the aircraft payloads for this mission," said Ramesh Kakar, GRIP program manager at NASA Headquarters. "Now that we are just a few weeks away from starting the field experiment, we can hardly hide our excitement."
Like a hurricane?
From late spring to early fall, the west coast of Africa spits out what are called African easterly waves almost like clockwork every few days. Some of these swirling systems become hurricanes. Most do not.
"The genesis part of this campaign is really focused on under what conditions these waves become tropical storms and hurricanes, and why some fizzle out and become nothing," said Kakar. "And when a tropical storm becomes a hurricane, we are trying to determine whether this will sputter or rapidly intensify."
These are always the great questions of hurricane season for people who live on coastlines or whose livelihoods might be threatened by a monster storm. But they also remain key questions for scientists who have devoted their careers to better understanding these powerful meteorological phenomena.
"We know the basic ingredients needed for a storm to form; high sea temperatures, low vertical wind shear, etc.," said Scott Braun, a research scientist at Goddard Space Flight Center in Greenbelt, Md., and a member of the GRIP science team. "But we also know that only 10 to 20 percent of African storm systems ever become hurricanes. What we don't know is why those few become hurricanes and the majority don't."
Delving deeper into the physical processes driving tropical cyclones, the questions only start to multiply. What roles do Saharan dust and other aerosols play? Does a vortex start from the bottom and work up, or does it begin from a higher altitude and work its way down? Do the massive "hot towers" of convection occasionally present near the inner eye walls of a hurricane cause the vortex to intensify, or are they a response to that intensification? Does the large-scale environment play a significant role in cyclone formation, or are smaller, cloud-scale processes more important?
"Just how the vortex, the circulation, develops in a tropical system is still a question," said Gerry Heymsfield, a Goddard research meteorologist and a member of the GRIP science team. "You might have a bunch of clouds and convection, but no spinning. How does the vortex really get going?
"We're just not sure about the processes," Heymsfield said. "There's been a lot of modeling and theory. These need to be verified, and it's difficult to do."
Where GRIP comes in
GRIP is designed specifically to put new, advanced instruments in positions they've rarely been before – observing what is happening at these critical moments of genesis and intensification. And it is designed to help answer some of these fundamental questions about hurricane physics and meteorology.
GRIP scientists will work in concert with NOAA's Intensity Forecasting Experiment (IFEX) and the National Science Foundation's (NSF) Pre-Depression Investigation of Cloud-systems in the Tropics (PREDICT) campaigns. The joint effort could allow as many as six aircraft to observe a single storm at once. NASA scientists and technicians are working on the campaign from NASA Headquarters, Goddard Space Flight Center, Jet Propulsion Laboratory, Langley Research Center, Dryden Flight Research Center, Ames Research Center, Marshall Space Flight Center and Johnson Space Center. Plus, the campaign is pulling in scientists from NOAA, the National Center for Atmospheric Research, and multiple universities.
The three sister campaigns will be able to fly complementary instruments at the same time to gain added insight into cyclone formation and behavior that wouldn't be possible if the campaigns were conducted alone. NOAA's IFEX is a multi-year project headed by its Hurricane Research Division to ultimately improve the forecasting of hurricane strength at landfall, while NSF's PREDICT is focused more closely on the science behind cyclogenesis.
NASA's DC-8 will fly out of Ft. Lauderdale, Fla., and fly at altitudes between 35,000 to 40,000 feet. The GRIP science team will also be based in Ft. Lauderdale. The WB-57 will be based at Ellington Field, near Johnson Space Center in Houston, and fly over storms at about 55,000 feet. The Global Hawk, with its 30-hour flight range, will take off and land from and be piloted remotely at Dryden Flight Research Center in California.
Three NASA satellites will play a key role in supplying data on tropical cyclones while the field mission is in progress. The Tropical Rainfall Measuring Mission, or TRMM, that is managed by both NASA and the Japanese Space Agency will provide rainfall estimates and help pinpoint "hot towers" within tropical cyclones. NASA's CloudSat and Aqua satellites will provide key data on clouds and fundamental meteorological factors – such as temperature, air pressure and precipitation.
Insight from GRIP data could eventually be used to improve the weather prediction models used by forecasters to predict hurricane track and intensity, but the primary scientific objective is simply to gain a better understanding of these critical stages in a storm's lifecycle. With that as a goal, and with the aircraft and instruments at hand, the science team is anxious to see the data come in.
"I think the potential science impact is tremendous for this field campaign," said Braun.
GRIP field campaign website
Global Hawk Completes First Science Flight
NASA's Earth Science News Team