Press Release

NASA Scientists Become Hurricane Chasers

By SpaceRef Editor
August 16, 2001
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Scientists from NASA’s Jet Propulsion Laboratory, Pasadena, Calif., will head into
hurricanes this summer, hoping to improve predictions of these deadly storms by using
new data-collecting technology.

The four scientists are part of NASA’s fourth Convection and Moisture Experiment,
a massive field experiment based at Jacksonville Naval Station, Fla., from Aug.16 through
Sept. 24. Their instruments will be on two NASA aircraft as they fly over, through and
around selected hurricanes in the Caribbean, the Gulf of Mexico and the Atlantic.

The goal of the experiment is to take the mystique out of hurricanes. By examining
how a hurricane evolves and behaves, investigators hope to make possible more accurate,
longer-range forecasts. Since evacuation is often the key to saving lives during a hurricane,
researchers are paying special attention to a hurricane’s behavior when it hits land.

Participants in this year’s Convection and Moisture Experiment from JPL include:

–Bjorn H. Lambrigtsen, who led the team that designed and built the High Altitude
Monolithic Microwave Integrated Circuit Sounding Radiometer for this mission. An
advanced atmospheric microwave sounder, the instrument can “see” through clouds. On
previous investigations of this project, two separate microwave sounders recorded
temperature and humidity. This new instrument, smaller and lighter than its predecessors,
will have the ability to do both.

The radiometer will fly in one of the wing pods of the high-altitude Earth Research-
2 aircraft, a former U2 spy plane. From an altitude of about 20 kilometers (65,000 feet), it
will scan the atmosphere below the plane from side to side with a searchlight-type beam
and map the temperature, humidity and cloud distributions inside a hurricane.

Lambrigtsen and his team will participate in all flights of the Earth Research-2
craft. From their instrument’s measurements, they will derive vertical profiles of
temperature, water vapor and liquid water. They will also estimate rain rates and create an
ice-particle scattering index, which will be used to develop a formula for calculating cloud
ice. Co-investigators are Drs. Lance Riley and Evan Fishbein, also from JPL.

— Dr. Robert Herman, who will lead the JPL Laser Hygrometer team. The laser
hygrometer is a miniature laser spectrometer for rapid measurements of water vapor.
During this mission, the instrument will be mounted on a NASA DC-8 aircraft to measure
water vapor as the airplane flies through tropical hurricanes. The data will help scientists
understand just how much moisture the air can hold before ice clouds form. The instrument
will also provide information on latent heat, the heat released when water condenses,
which is an important energy source that drives storms. These data should provide a better
understanding of the processes that regulate water in the atmosphere and tropical storms.

— Dr. Michael Mahoney, the principal investigator for the DC-8 Microwave
Temperature Profiler and the Earth Research-2 Microwave Temperature Profiler. The
instruments scan vertically in each aircraft’s flight direction. Looking straight down,
straight ahead and straight up, they measure temperature at different frequencies to create a
complete temperature profile.

On the DC-8, the Microwave Temperature Profiler displays air temperature data in
real-time and is updated every 15 seconds. An experimenter onboard the DC-8 can control
this real-time data and provide it to scientists immediately. The temperature profile of the
atmosphere is a vital part of hurricane research because it helps scientists understand the
stability of the atmosphere. The instrument can also help pinpoint the exact location of the
troposphere, the lower part of Earth’s atmosphere. In addition, it can measure the flow of
air parcels to determine if there are gravity waves in the atmosphere that could affect the
level of ozone depletion.

On the Earth Research-2 aircraft, the microwave temperature profiler operates
autonomously, and the data is processed later.

— Dr. Eastwood Im, who will administer the Dual Frequency Airborne
Precipitation Radar, an airborne dual-frequency radar that will measure the 3-D structure
of rainfall. Two crucial parts of the new instrument — the pressure box and antenna — are
from a previous airborne radar developed by JPL, called Airborne Rain Mapping Radar.
The new instrument is an improvement over the earlier radar because it has two
frequencies, which will improve rainfall measurements, and can process data in real time.

The instrument team plans to fly this radar in a rotating figure-four pattern across
the rainstorm through the hurricane’s eye, as well as through the rainbands at the storm’s
edge. Data collected will help determine rain rate, vertical motion and location of melting
ice along the DC-8 flight track below the aircraft.

The fourth Convection and Moisture Experiment is sponsored by NASA’s Earth
Science Enterprise. These investigations will be conducted in collaboration with the
National Oceanic and Atmospheric Administration’s Hurricane Research Division and the
U.S. Weather Research Program. JPL is a division of the California Institute of
Technology in Pasadena.

SpaceRef staff editor.