Joining the Hunt
When a hurricane makes its way to shore, the damage it brings can be devastating.
People in the storm's path may lose their homes, or those homes may sustain severe damage that could take weeks or even months to repair. Towns may be destroyed and, in the worst cases, lives may be lost.
In the United States, 100 million people live within 50 miles of the coast and that means they're vulnerable to experiencing what a hurricane can do. And while these Americans may have plenty of warning when a hurricane is on the way, it's much more difficult to predict how intense the storm will be once it arrives.
The team behind the NASA Hurricane and Severe Storm Sentinel, or H3 mission, hopes to change that by using two NASA Global Hawk Unmanned Aircraft Systems to help study storm intensity. One Global Hawk is equipped with NovAtel's Synchronized Position Attitude Navigation (SPAN®) technology to ensure researchers obtain accurate navigation data along with accurate Doppler radar data, says Gerry Heymsfield, the principal investigator for NASA's HIWRAP radar and research meteorologist at NASA's Goddard Space Flight Center. This data helps scientists better predict how intense a hurricane will be once it makes landfall, and what factors cause it to intensify.
HIWRAP, which stands for High-altitude Imaging Wind and Rain Airborne Profiler, maps 3D winds and precipitation within hurricanes and other severe weather events. A NovAtel SPANSE™ receiver is located near the HIWRAP instrument to help researchers improve measurement accuracy and easily obtain the most accurate attitude and positioning data possible. Knowing what causes hurricanes to intensify will eventually help improve hurricane forecasts, potentially reducing the damage they bring and the lives they take. There's a big difference between a Category 1 and a Category 3 hurricane, and knowing which to expect can help people properly prepare for a storm-even if that means evacuating to get out of its path.
“We basically want to know what makes hurricanes intensify rapidly,” Heymsfield says of the HS3 mission. “We don't always know why they intensify rapidly in 6 to 12 hours. The mission will help better predict the processes that cause rapid intensification of storms. Say a storm gets near the coast. Then we're worried about if it will intensify or not. This information will help better predict that.”
The five-year mission began with the planning stages in 2010, and continued with flights from August to September in both 2012 and 2013. The mission wraps up after this year's hurricane season, and will give scientists the information they need to better determine the processes that lead to those intense, devastating hurricanes that cost an average of $10 billion in damage every year-and to better forecast them.
The Global Hawk Unmanned Aircraft Systems overcome several limitations that once kept researchers from studying how hurricanes evolve and why. Not only can they fly to an altitude of about 60,000 feet-about twice as high as a commercial airliner-and as far as 12,600 miles, they also can fly for about 26 hours, according to NASA. This gives researchers the time, distance and altitude they need to collect continuous, high-resolution measurements that will help better predict storm intensity.
“They have very long endurance,” Heymsfield says. “They can fly for about 26 hours or so, and for studying a hurricane far out in the Atlantic Ocean, we need at least this much endurance for the plane to fly over the storm far from the coast. Any plane with a pilot is limited to 8 hours or so of flight time. This allows us to study storms way out over the ocean.”
Altitude is important too, Heymsfield says, because it enables researchers to get a better look inside the storms with the state-of-the art science instruments the Global Hawks use to study tropical storms and hurricanes. “We measure the structure of storms any where there is precipitation and clouds that the radar can detect,” Heymsfield says. “We measure the wind velocity and wind speeds within a storm. By looking at these winds it helps us understand how a storm intensifies.”
During this mission, according to NASA, scientists want to use data from the Global Hawk flights to answer three main questions-what role does the large-scale environment, particularly the Saharan Air Layer (SAL), have on intensity change, what is the role of storm internal processes such as convective towers, and to what extent are these intensification processes predictable. The two Global Hawks that are part of the HS3 mission are equipped with different payloads. The environmental payload is responsible for monitoring the environment around the storms looking for conditions that are “favorable for storm formation and intensification,” according to NASA. The state-of-the art weather instruments that make this possible are the scanning High-resolution Interferometer Sounder (S-HIS), the AVAPS dropsonde system, theTWiLiTE Doppler wind lidar, and the Cloud Physics Lidar (CPL). This Global Hawk is involved with studying the role SAL has on storm formation and intensification.
The over-storm payload, which features NovAtel's SPAN technology, repeatedly flies directly over storms to “collect data on the inner-core structures that lead to storm intensity change,” according to NASA. This Global Hawk is not only equipped with the SPAN system, it also collects field measurements using HIWRAP conically scanning Doppler radar. The radar works in conjunction with the SPAN technology, the HIRAD multi-frequency interferometric radiometer, and the HAMSR microwave sounder.
NovAtel technology at work
While the Global Hawks provide hurricane data that researchers wouldn't otherwise be able to obtain, that data must be accurate. That's where NovAtel's SPAN technology comes in.
NovAtel is the leading provider of high-precision GNSS technology for unmanned systems making it a natural fit for the HS3 mission. NovAtel technology has been used in Unmanned Aircraft Systems, Unmanned Airborn Vehicles and Unmanned Ground Vehicles, and in a range of applications from homeland security to aerial survey to mine detection.
The over-storm payload Global Hawk is equipped with a NovAtel SPAN-SE receiver which provides the user interface to SPAN and outputs raw measurement data or solution data over several communication protocols or to a removable SD card.
As the principal investigator on the HIRWAP radar, Heymsfield works closely with the SPAN-SE technology. His primary role is to work with the radar measurements and retrievals, which is deriving the winds from the radar measurements in the storm.
“We're not doing anything in real time. We're doing post-processing,” Heymsfield said. “What we do is use the post-processed data to improve the accuracy of winds obtained from HIWRAP. We have to know the attitude of the airplane so we can remove any winds that are caused by the aircraft itself. We want to look at the winds in the storm, so we have to remove any effects of the aircraft. That means we need an accurate position and attitude of the plane.”
Heymsfield and his team use the SPAN-SE with an LN-200 IMU to provide high-accuracy attitude and position data. They can get this information from the aircraft, Heymsfield says, but the SPAN technology provides it at a higher data rate-of up to 200 Hz.
The SPAN receiver is located on top of the Global Hawk's HIWRAP radar, so it is more accurate than the aircraft system that is located about 20 feet forward of the radar location, Heymsfield says.
“It [SPAN] allows us to have high quality navigation data along with our radar data,” Heymsfield says. “It makes it easier to correct for the aircraft motions, and it makes data more accurate.”
Another way NASA uses NovAtel technology to study weather
Also in 2014, NASA used NovAtel technology in an experiment that isn't related to hurricanes. IPHEx, or the Integrated Precipitation and Hydrology Experiment,” seeks to characterize warm season orographic precipitation regimes, and the relationship between precipitation regimes and hydrologic processes in regions of complex terrain,” according to data provided by the IPHEx experiment, Civil and Environmental Engineering, Duke University, North Carolina.
The experiment included an Intense Observing Period (IOP) from May-July of 2014 post GPM launch, which is the Global Precipitation Mission, according to the website. GPM is an international satellite mission to “provide next-generation observations of rain and snow worldwide every three hours.” The observing period focused on 4D mapping of the precipitation structure. The NASA ER-2 and the UND Citation aircraft conducted high altitude and “in the column” measurements.
The ER-2 plane is equipped with multifrequency-radiometers (AMPR and CoSMIR), the dual-frequency Ka-Ku band, HIWRAP Ka-Ku band, CRS W-band, and EXRAD X-band radars. A NovAtel SPAN-SE and a ProPak-V3, both, triple-frequency GNSS receivers that track GPS+GLONASS were used.
Even though 2013 was a quiet hurricane season, the Global Hawks did manage to obtain important data that will help researchers better understand rapid storm intensification, according to NASA.
The over-storm Global Hawk flew over Hurricane Ingrid on Sept. 15, 2013 according to NASA. The storm moved through the extreme southwestern Gulf of Mexico, traveling west-northwestward along Mexico's east coast. The plane's Hurricane Imaging Radiometer, HIRAD, measured energy coming from the rough ocean surface caused by rain and strong winds, enabling it to identify an area of heavy rain and likely strong winds on the storm's eastern side.
The environmental payload Global Hawk flew over the remnants of Tropical Storm Erin to capture data on the SAL in the Eastern Atlantic Ocean, obtained data from Tropical Storm Humberto, studied a storm that had a 70 percent chance to develop but never did, and analyzed the environment of Tropical Depression 7, which would become Tropical Storm Gabrielle.
The GRIP Experiment
The HS3 mission isn't the first time NASA used NovAtel's SPAN technology to obtain accurate navigation measurements. NASA first used SPAN during 2010 in an experiment known as GRIP-the Genesis and Rapid Intensification Processes. This six-week mission was conducted to help better understand how tropical storms form and develop into major hurricanes, according to NASA.
During this experiment, a Global Hawk gathered data from Hurricane Karl, a Category 3 hurricane that made landfall in Mexico, leaving nearly half a million people without power and 20,000 damaged or flooded homes. It also studied Hurricanes Earl and Matthew.
The HIRAD instrument on board the Global Hawk was able to measure strong ocean winds through heavy rain during Karl, providing both rain rate and wind speed. “We've learned that we've been able to derive winds within a storm,” Heymsfield says.
“We had 12 different passes over Hurricane Karl and we were able to put together an evolution and time sequence of pictures of the storm intensifying.”
The Data Matters
Studying hurricanes and why they evolve is challenging. While researchers have made progress on accurately predicting the path of a storm, determining how intense the storm will be once it lands has proven more difficult.
The two Global Hawks that are part of the HS3 mission make it possible to study the processes that lead to intense, devastating hurricanes. These high-altitude Unmanned Aircraft Systems carry the equipment needed to study these storms and have the endurance necessary to travel to storms in the Atlantic, storms researchers couldn't study close up before.
When the HS3 team collects the last field measurements for the mission in 2014, that data, along with what they've already collected, will lead to a better understanding of what causes storms to grow stronger and how to forecast intense, potentially devastating hurricanes well before they make landfall. The high-altitude, long endurance Global Hawks give researchers the opportunity to gather a wealth of data that will help them better understand and predict how these storms evolve.
As a leader in precision GNSS technology to the unmanned industry, NovAtel's SPAN is well suited for a mission like HS3, providing researchers with the accurate navigational data they need to account for the plane's attitude and position.
“It's very important we have good navigation data measured close to our radar,” Heymsfield says. “We could do it other ways, but I think it [SPAN-SE] has been very good for us. It's been useful. It makes it easier to process the data and we understand the data better.”
And that data will help those in a hurricane's path better prepare for what's coming their way.