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April 24, 2003
Hurricane Winds Carried Ocean Salt & Plankton Far Inland
Researchers found surprising evidence of sea salt and frozen plankton
in high, cold, cirrus clouds, the remnants of Hurricane Nora, over the
U.S. plains states. Although the 1997 hurricane was a strong eastern
Pacific storm, her high ice-crystal clouds extended many miles inland,
carrying ocean phenomena deep into the U.S. heartland.
Kenneth Sassen of the University of Utah, Salt Lake City, and University
of Alaska Fairbanks; W. Patrick Arnott of the Desert Research Institute
(DRI) in Reno, Nev.; and David O. Starr of NASA's Goddard Space Flight
Center, Greenbelt, Md., co-authored a paper about Hurricane Nora's far-reaching
effects. The paper was published in the April 1, 2003, issue of the American
Meteorological Society's Journal of Atmospheric Sciences.
Scientists were surprised to find what appeared to be frozen plankton
in some cirrus crystals collected by research aircraft over Oklahoma,
far from the Pacific Ocean. This was the first time examples of microscopic
marine life, like plankton, were seen as "nuclei" of ice crystals in
the cirrus clouds of a hurricane.
Nora formed off the Panama coast, strengthened as it traveled up the
Baja Peninsula, and the hurricane crossed into California in September
1997. Over the western U.S., Nora deposited a stream of high cirrus,
ice crystal, clouds that created spectacular optical effects, such as
arcs and halos, above a broad region including Utah and Oklahoma. That
stream of cirrus clouds enabled researchers to analyze growth of ice
crystals from different nuclei.
Different nuclei, like sulfate particles, sea salt and desert dust,
affect ice-crystal growth and shape. Torn from the sea surface by strong
hurricane winds, sea salt and other particles from evaporated sea spray
are carried to the cold upper troposphere in storm updrafts, where the
drops freeze and become ice crystals. Plankton, a microscopic organism,
is also likely present in the sea spray and is similarly lofted to high
levels.
"Understanding how ice crystals grow and what determines their shapes
is important in understanding how they interact with sunlight and infrared
energy," Starr noted. "These interactions are important processes in
the global climate system. They are also critical to sensing cloud properties
from space, where NASA uses measurements of the reflected solar radiation
to infer cloud physical properties, such as ice-crystal size," he said.
Data were gathered using ground-based remote sensors at the Facility
for Atmospheric Remote Sensing in Salt Lake City and at the Clouds and
Radiation Testbed in northern Oklahoma. A research aircraft collected
particle samples over Oklahoma. Observations from the Geostationary Operational
Environmental Satellite 9 (West), launched by NASA and operated by the
National Oceanic and Atmospheric Administration, were also used. DRI
analyzed the ice crystals collected from Nora.
Scientists were using data generated through the U.S. Department of
Energy (DOE) Atmospheric Radiation Measurement (ARM) Program. The ARM
Program's purpose is obtaining field measurements and developing computer
models of the atmosphere. Researchers hope to better understand the processes
that control the transfer of solar and thermal infrared energy in the
atmosphere, especially in clouds, and at the Earth's surface.
The ARM energy measurements also double-check data from the Moderate
Imaging Spectroradiometer (MODIS) instrument aboard NASA's Terra and
Aqua satellites. By ensuring the satellites are recording the same energy
reflected and absorbed by clouds from Hurricane Nora as those provided
by the ground data in this study, scientists hope to take fewer ground
measurements in the future, and enable the satellites to provide the
data.
The DOE ARM program, National Science Foundation, and NASA's Earth Science
Enterprise funded this research. The Earth Science Enterprise is dedicated
to understanding the Earth as an integrated system and applying Earth
System Science to improve prediction of climate, weather and natural
hazards, such as hurricanes, using the unique vantage point of space.
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Contacts:
Elvia H. Thompson
Headquarters, Washington
(Phone: 202/358-1696)
Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-4044) |
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 Hurricane
Nora Brings Frozen Plankton to U.S. Plains and Creates Spectacular Halos
Hurricane Nora near Baja California on 22 September
1997 1800 UT (10AM Pacific Time), as viewed by the NOAA GOES-9 satellite.
The image is a false color composite created from the visible, 4 micron
and 11 micron channels. CREDIT: Laboratory for Atmospheres, NASA/GSFC
 Hurricane
Nora's Halo
This is a photograph of one of the spectacular halos
created by the ice crystal clouds in Hurricane Nora's outer bands. It
was taken in Salt Lake City, Utah, on September 25, 1997. CREDIT: Gerald
(Jay) Mace, University of Utah.
 Plankton
and Microbes in Cloud Ice Crystals
These ice crystals in the shapes of plates and columns
show central features resembling plankton and other microbes ranging
from a few microns up to ; 40 microns in maximum dimension. A micron
is one-millionth of a meter, or about 40 millionths of an inch. Note
the apparent algae cell at the center of the broken plate crystal (top
right), which displays features of cell morphology. CREDIT: Desert Research
Institute
 Hurricane
Nora's Path
This graphic depicts the path that Hurricane Nora took
from its development west of Panama on September 16th where it strengthened
from a low pressure area into a tropical storm that day. On the 17th
Nora was a hurricane. The numbered boxes on the graph represent the location
of Nora on that day. Nora remained a hurricane during landfall, then
brought winds and rains from California and Arizona to the central Rockies,
with some moisture making it into the northern Plains. CREDIT: NOAA/
National Weather Service/NCEP/ Hydrometeorological Prediction Center
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