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Scientists analyzing immense data haul from hurricanes

Convection and Moisture Experiment will provide new insight on killer storms

Jan. 15, 1999: An eye that winked, a rain of ice crystals, and striking lightning show that hurricanes lead more complex lives than anyone had suspected. More details - and fuller understanding - will come in the next year as scientists analyze thousands of hours of data collected during the most comprehensive hurricane study project ever conducted.

Right: A series of images depicts a section of Bonnie as seen by the Multispectral Atmospheric Mapping Sensor (MAMS, strips 1 and 2) and the Advanced Microwave Precipitation Radiometer (AMPR, strips 4-6) carried by the ER-2 over Hurricane Bonnie on August 26, 1998. These depict cloud cover and cold cloud tops in visible and infrared light, and rainfall and ice distribution as seen in microwave bands. Links to 416x696-pixel, 107KB JPG. Credit: NASA.

"Although these opportunities do not provide immediate comfort to those who directly experienced this season's devastating storms," said Robbie Hood of NASA's Marshall Space Flight Center. "The wealth of information collected by all the agencies will lead to better hurricane forecast capabilities in the future."

Hood was the lead mission scientist on the third Convection and Moisture Experiment (CAMEX-3), an ambitious project that brought together researchers from NASA, the National Oceanic and Atmospheric Administration, and the U.S. Air Force Reserve, and their associates in universities and the weather industry.

"The real success of CAMEX-3 was the breadth of hurricane information collected," said Ramesh Kakar, program manager at NASA Headquarters. "The combination of scientists from eight NASA centers, and the multi-agency, multi-university teamwork of CAMEX-3 was a tremendous example for the nation."

Left: The ER-2 Doppler radar provides a dramatic cross-section view of Hurricane Georges' eye over Hispaniola. The Dominican Republic received heavy rain during this pass, as seen in the radar image at top, and subsequent rain eventually caused significant loss of life. The rain was enhanced significantly by the mountains in the interior of the island. The mountains are about 2.7 km high (9000 ft) and produced what appears to be a huge thunderstorm over the mountains as shown in the blue - upward rising - moisture in the lower image. Significant research will be done to understand this very complicated interaction between Hurricane Georges and the mountains. Links to 518x664-pixel, 156KB GIF. Credit: NASA.

Kakar cited the assistance to NASA from numerous universities, the pilots and crews from Dryden Flight Research Center, and the project management staff from the Ames Research Center as keys to the success of CAMEX. "We are very grateful for the advice and coordination efforts of the National Oceanic and Atmospheric Administration, and the support from the Air Force Reserve 53rd Weather Squadron, and the help from Federal Aviation Administration allowed the CAMEX-3 investigators to capitalize on key research opportunities when they arose."

A 4-page print copy of this report, also including the flight log,
is available on line as a 211KB Acrobat 3.0 PDF file.
High-resolution copies of the images used here and in the fact sheet are available.

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Probing high for answers

Although meteorologists have been observing hurricanes for decades, mysteries remain. Scientists can predict where hurricanes will go in the next 24 to 48 hours, but remain uncertain of how much strength a hurricane will gain, or exactly how it will change when it makes landfall.

Part of the answer lies at high altitudes, two to three times higher than NOAA and Air Force aircraft that routinely scout hurricanes, and inside the cloud tops which weather satellite cameras cannot penetrate.

Right: This image by the Airborne Rain Mapping Radar (ARMAR) on the DC-8 shows shows a vertical slice through the northern eye wall of Hurricane Bonnie on Aug. 24. The slice is 65 km (40 mi) along the ground and 9 km (5.6 mi) up from the ocean surface (the white line; the below-surface image is a mirror-image return). The most intense precipitation, yellow and white at left, is the eye wall. Additional, less intense rain can be seen to the right (north) of the eye wall. In addition to the rain in the lower portion of the image, the ARMAR also sees ice-phase precipitation at higher altitudes (above about 5 km [3 mi]). The signal from ice particles is less strong than from liquid precipitation (rain) and is shown in red. The ice-phase particles are most likely aggregates (i.e., snow), which is typical at higher levels in storms even in the tropics. Also, to the left of center is a gap, or area of weak signal, can be seen between the eye wall and the rain to the right. Hurricanes typically have rain organized into spiral bands with gaps between bands. Links to 639x443-pixel, 165-KB JPG. Credit: NASA.

The first two CAMEX campaigns were smaller NASA efforts. For CAMEX-3, NASA approached NOAA about coordinating with NOAA's regular hurricane reconnaissance flights so that larger data sets could be collected.

"We felt like NASA had something to contribute by providing remote sensing experience to the other agencies," Hood said.

At the core of CAMEX-3 were two NASA aircraft, its DC-8 Airborne Laboratory equipped with wind-sounding lasers, lightning detectors, radar, and other instruments, and an ER-2 high-altitude jet with lightning, radar, and microwave sensors.

Teamwork

Where possible, the NASA flights were coordinated with NOAA's two P-3D Orion patrol aircraft and a Gulfstream jet. NASA will also use data collected by the Air Force Reserve 53rd Weather Squadron's WC-130 Hercules Hurricane Hunters.

In addition, NASA employed its weather station on Andros Island in the Bahamas, and the Tropical Rainfall Measuring Mission (TRMM) satellite.

Hood said the team was not sure what would happen during the Aug. 12-Sept. 23 period set aside for CAMEX-3.

Left: Lidar Atmospheric Sensing Experiment (LASE) measured profiles of water vapor (left) and aerosols and clouds when the DC-8 flew through the eye of Hurricane Bonnie on Aug. 26, 1998 just before the storm hit the east coast of the U.S. A broken cloud field was visually observed in Bonnie's eye. LASE measurements showed this eye to be quite large and revealed the precise altitudes of clouds within the eye. LASE also measured the vertical distribution of water vapor inside the eye of Bonnie during brief cloud free periods. These are the first lidar measurements of water vapor inside the eye of a hurricane. Water vapor, aerosol, and cloud measurements are in the full 713x461-pixel, 45-KB GIF. Credit: NASA.

The CAMEX team

CAMEX-3 employed a broad range of scientists, managers, and planners from several NASA centers and other organizations, including:

NASA centers: NASA Headquarters, Ames Research Center, Dryden Flight Research Center, George C. Marshall Space Flight Center (including the Global Hydrology and Climate Center), Goddard Space Flight Center (including Wallops Flight Center), Jet Propulsion Laboratory, Langley Research Center.

Other organizations: National Oceanic and Atmospheric Administration (Atlantic Oceanographic and Meteorological Laboratory and Hurricane Research Division); Florida State University, Massachusetts Institute of Technology, Texas A&M University, University of Maryland - Baltimore County, University of Wisconsin - Madison; and Desert Research Institute, Simpson Weather Associates.

The full organization and its contacts are listed on line.

What they got were four major hurricanes - Bonnie, Danielle, Earl, and Georges - and a tropical storm - Hermine.

"Each of the hurricanes we sampled was different, so we think that was a great accomplishment to get so much different data," Hood said. "These kinds of data at these altitudes have not been collected before as a body."

The CAMEX-3 team now has more than 132 flight hours of data, which translates into several thousand hours of observations by the more than 30 instruments carried by the many aircraft or deployed into the storms.

The analysis will take several months as scientists study their own data then confer with each other.

Meanwhile, a number of early findings are emerging.

Complex answers

"The inflow and outflow wind patterns were much more complicated than we expected," Hood said. The direction and strength of the wind patterns are a measure of the energy flow within the hurricane, and and may help predict its future.

Left: This plot illustrates the much colder cloud tops found in the eye wall in association with the thunderstorms compared to the relatively calm region of Bonnie's eye on Aug. 24. This image by the NPOESS Aircraft Sounder Testbed - (NAST-I) depicts the infrared spectrum in two locations of the storm - the eye (in red) and in the eye wall (blue). The full 687x684-pixel, 40KB GIF includes an infrared image was generated using the spectra themselves to provide a visual representation of the storm. Credit: NASA.

The best sights of the campaign were reserved for ER-2 pilot Dee Porter as he flew over hurricane Georges over the island of Hispaniola, in what Hood called "the most significant lightning measurements during the entire campaign." As Georges stomped across Hispaniola, the island's 2.7 km (9000 ft) mountain range caused a large bump to form in the middle of the storm.

"The clouds went down like a moat and came up like a wedding cake, and the ring around the cake was filled with lightning," she continued. "The pilot was pretty impressed." He also reported seeing reddish purple lightning jets rising from the cloud tops and seemingly reaching for space.

"The amazing thing about this data from (Hurricane) Georges is that the rain is enhanced significantly by the mountains in the interior of the Dominican Republic," said Gerry Heymsfield of NASA's Goddard Space Flight Center. "We got a glimpse of an example of the impact of the storms with a mountainous island and the subsequent rain which eventually caused significant loss of life. Understanding this very complicated interaction between Hurricane Georges and the mountains will keep us busy for a while."

In the wink of an eye

Another surprise came when hurricane Bonnie "winked" at the research team.

During successive passes by the DC-8 on Aug. 24, Bonnie's eye changed shape.

"I had no idea that the position or structure of the eye would change that fast," Hood said. "It was pulsating; it was undulating."

Left: The Lightning Instrumentation Package (LIP) aboard the ER-2 shows changes in the electrical field as the aircraft passed through two charge centers in Hurricane Georges. The square waves at the start and center are self-calibration pulses. Two large lightning flashes occurred during the first crossing; several smaller lightning flashes occurred during the second crossing. The total number of lightning flashes on this plot (one hour) is about an order of magnitude less than what is typically seen for an over-land thunderstorm. Also, not all hurricanes exhibit lightning. It is thought that the occurrence of lightning in a hurricane is an indicator that intensification is underway. The full 684x916-pixel, 19KB GIF shows lightning traces by the upper and lower bay instruments, and the difference between the two. (Credit: NASA)

Storms are more than clouds; winds in clear air play a major role, so CAMEX-3 employed two laser sounding instruments to probe the hurricanes.

The MACAWS Doppler laser - which uses laser light like a police radar to measure speed - measured winds in the clear regions between cloud decks and in the eyes.

Web Links
NASA, NOAA team seeks secret of hurricane's power. Aug. 12, 1998. CAMEX-3 preview story.
Quite a Windfall. Aug. 31. Hurricane team completes first half of unique science campaign. Lists aircraft and spacecraft used in CAMEX-3.
NASA gives Georges two last looks. Sept. 28. CAMEX-3 ends. Includes log of all flights.

Laser scanners

"These are the first wind measurements made in the eye wall of a hurricane with Doppler lidar," explained Jeffry Rothermel of the GHCC.

The LASE from NASA's Langley Research Center used its laser in a different manner, to measure water vapor and aerosols (suspended particles), also in clear air.

Right: The Multicenter Airborne Coherent Atmospheric Wind Sensor (MACAWS) produced the first hurricane eye wall wind measurements during a pass through Hurricane Bonnie on Aug. 26. In the full 860x422-pixel, 54KB JPG shows arrows indicating wind direction and relative speeds. Credit: NASA.

When the DC-8 flew southeast of the Hurricane Bonnie on August 26, 1998 just before the storm hit the east coast of the U.S., LASE showed high concentrations of water vapor streaming into the hurricane. These LASE water vapor measurements will be used in numerical models to help understand the behavior of Hurricane Bonnie as it approached the coast.

LASE also measured water vapor profiles and aerosols as the DC-8 flew through the eye of Bonnie during brief cloud free periods. These are the first lidar measurements of water vapor inside the eye of a hurricane.

"CAMEX was successful on many different levels," Hood said. "We collected three-dimensional data sets on several storms, and we had good multi-agency cooperation."

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Author: Dave Dooling
Curator: Linda Porter
NASA Official: Gregory S. Wilson