Caption for Image 1: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
Caption for Image 2: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.
Caption for Image 3: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
Caption for Image 4: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
Caption for Image/Animation 5:MOVIE OF HURRICANE NORA BEFORE LANDFALL
This animation from NOAA's GOES satellite shows a Category 1 (Saffir-Simpson Scale) Hurricane Nora moving slowly north/northwest along the Mexican coast. Estimated wind speeds are about 80 mph and the eye is about 50 nautical miles across. At this time, the hurricane was 32-40 hours prior to landfall. Intertropical Convergence Zone (ITCZ) in the lower portion of the animation is where tropical winds come together. The ITCZ ranges from about 5° north and south of the equator. It's where the northeast trade winds and southeast trade winds converge. TEXT CREDIT: Katy Ginger, DLESE Program Center, UCAR ANIMATION CREDIT: the Cooperative Program for Operational Meteorology, Education, and Training (COMET) Web site atof the University Corporation for Atmospheric Research (UCAR) pursuant to a Cooperative Agreement with National Oceanic and Atmospheric Administration. Copyright 1997-2002 UCAR. All Rights Reserved.
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.
This Flash animation from NOAA's GOES satellite shows a Category 1 (Saffir-Simpson Scale) Hurricane Nora moving slowly north/northwest along the Mexican coast.