From: Editor, ENN
Published May 27, 2009 06:55 AM
NASA Supercomputers Advance State of the Art of Ocean
Circulation Modeling
Global scale oceanic circulation modeling has been moving to a new
gridding method that projects the faces of a cube onto the surface of a
sphere. They found that this method covers the sphere more uniformly than a
latitude-longitude grid, and that it produces more accurate results near
Earth's poles. This is helping refine modeling of ocean currents which are
critical to global climate models, and has the potential to significantly
improve the accuracy of climate change modeling.
Researchers from NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif.
and Massachusetts Institute of Technology (MIT), Cambridge, Mass are reaping
huge benefits from research performed on NASA's advanced supercomputers.
Scientists believe the ocean and its interactions with the atmosphere are
key to studying climate change. To better understand these interactions,
they identified three important areas in climate research. They look at the
'states' of the ocean and sea-ice, which includes their temperature,
salinity, current speeds, and sea-surface elevation, and study their changes
at and below the surface. They also look at the 'state' of the atmosphere,
which includes its temperature, humidity, and wind patterns, and study how
it was affected by the changes in the ocean. These interactions between the
atmosphere and ocean directly affect the weather. The scientists study the
biological activity in the ocean and its responses to the changing 'state'
of the ocean. These are important variables in the models, and require the
most detailed treatment to be most accurately addressed.
In the past, the standard model gridding methods, using longitude and
latitude, had difficulty assimilating data at the poles. To solve this
problem, researchers started looking at the world in a new way, using a new
cube-based method. But advanced computers and algorithms were needed to
enable modeling at higher resolutions, said Hill.
These improvements have increased the accuracy of ocean data syntheses to
such an extent that they are starting to resolve ocean eddies and other
narrow currents, which transport heat, carbon, and other properties within
the ocean.
NASA Supercomputing Goes Green: Modeling Earth's Ocean Climate
05.18.09
Earth scientists are reaping huge benefits from research performed on NASA's
advanced supercomputers. New cube-based simulations are helping to improve
estimates of ocean circulation and climate.
Researchers from NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif.
and Massachusetts Institute of Technology (MIT), Cambridge, Mass., are using
a new gridding method that projects the faces of a cube onto the surface of
a sphere. They found that this method covers the sphere more uniformly than
a latitude-longitude grid, and that it produces more accurate results near
Earth's poles.
The
animation shows ocean surface current speeds evolving in time (Jan. 1993
to Dec. 2002) and projected onto the cube grid. Red are faster surface
currents (for example the Gulf Stream).
Scientists believe the ocean and its interactions with the atmosphere are
key to studying climate change. To better understand these interactions,
they identified three important areas in climate research. They look at the
'states' of the ocean and sea-ice, which includes their temperature,
salinity, current speeds, and sea-surface elevation, and study their changes
at and below the surface. They also look at the 'state' of the atmosphere,
which includes its temperature, humidity, and wind patterns, and study how
it was affected by the changes in the ocean. These interactions between the
atmosphere and ocean directly affect the weather, according to Hill.
Finally, the scientists study the biological activity in the ocean and its
responses to the changing 'state' of the ocean.
"The day-to-day weather comes from the atmosphere state, but it is strongly
modulated by the ocean state. Other less apparent processes, such as the
carbon dioxide extracted from the atmosphere by the ocean, depend on the
oceans' physical and biological state," said Hill.
Following work begun by Carl Wunsch and colleagues at MIT as part of the
World Ocean Circulation Experiment, a NASA-sponsored project called
Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2), is
modeling the global ocean currents and their fluctuations, the changes in
temperature and salinity, and the growth and melting of sea-ice in the polar
regions.
The project's goal is to produce quantitative images of the state of the
ocean globally, including its evolution. These images use data from all
available NASA satellites and from on-site instruments, and are the result
of combining and assimilating these data into global full-ocean-depth and
sea-ice configurations built by the MIT general circulation model (MITgcm).
These data combinations, called data syntheses, help quantify the role of
the ocean in the global carbon cycle, explain the recent evolution of the
polar oceans, and monitor time-evolving balances within and between
different components of the Earth system.
The first Earth-orbiting satellite designed for remote sensing of Earth's
ocean was the Seasat mission, which was launched in 1978. Since then, NASA
has developed a series of ocean observing satellites that monitor sea
surface elevation and temperature, surface wind stress, and the ocean's
gravitational field. Part of this series is NASA’s Earth Observing System,
which is the data system used by ECCO2 today.
According to Dimitris Menemenlis, a JPL Earth scientist and ECCO2
researcher, the available oceanographic data will be enhanced by two
forthcoming satellites: the Aquarius and the Surface Water Ocean Topography
(SWOT) missions. Both satellites will provide different information that
will be assimilated into a single coherent picture of the ocean state.
Aquarius is due to launch in 2010 and will provide global maps of sea
surface salinity. The SWOT mission is still in development and aims to
observe sea surface elevation with unprecedented resolution and spatial
coverage.
In the past, the standard model gridding methods, using longitude and
latitude, had difficulty assimilating data at the poles. To solve this
problem, researchers started looking at the world in a new way, using a new
cube-based method. But advanced computers and algorithms were needed to
enable modeling at higher resolutions, said Hill.
"Currently, NAS is home to two of the fastest supercomputers in the world,
Pleiades and Columbia," said William Thigpen, NAS manager at Ames Research
Center. "NAS provides data analysis, visualization tools and support that
enable the exploration of huge data-sets that provide insights not
previously possible."
Initially, the cube-based computation was simulated on the NAS SGI Altix
system, Columbia, but was later moved to the NAS Pleiades cluster facility
to take advantage of the increased size and performance of the new
supercomputer's architecture. Over time and with improvements,
supercomputing evolved into 'green technology.' Using a total of 2.09
megawatts, or 233 megaflops per watt, Pleiades ranked number 22 on the
November 2008 Green500 list. This ranking makes Pleiades the second-most
powerful and energy-efficient supercomputer in the world.
According to Menemenlis, these improvements have increased the accuracy of
ocean data syntheses to such an extent that they are starting to resolve
ocean eddies and other narrow currents, which transport heat, carbon, and
other properties within the ocean. The importance of this endeavor is
recognized by numerous national and international organizations, such as the
World Meteorological Organization's World Climate Research Programme and the
United Nations Educational, Scientific and Cultural Organization's (UNESCO)
Intergovernmental Oceanographic Commission.
Ruth Dasso Marlaire
Ames Research Center, Moffett Field, Calif.
Article originally published:
http://www.nasa.gov/topics/technology/features/supercomputing_051409.html
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