|
The Clouds and the Earth’s
Radiant Energy System (CERES) instrument is
one of several scheduled to launch aboard the Earth Observing
System’s (EOS) Aqua spacecraft in 2002. Scientists will use
observations from the CERES instrument to study the energy
exchanged between the Sun; the Earth’s atmosphere, surface and
clouds; and outer space.
The CERES Aqua instruments will be the fourth and fifth CERES
instruments in orbit. NASA launched the first CERES instrument
aboard the Tropical Rainfall Measuring Mission satellite, or
TRMM, in November 1997. Results of
the TRMM mission show that the first CERES provided better
measurement capabilities than any previous satellite instrument of
its kind. Two other CERES instruments are currently orbiting the
Earth on the EOS Terra spacecraft, launched in late 1999. Early
CERES Terra results give new insights into the effects of clouds on
climate and how the climate system changes from decade to decade.
Two CERES instruments on each of the Terra and Aqua spacecraft will
provide global coverage of energy radiated and reflected from the
Earth. Scientists will use measurements from both satellites’
orbits to improve observations of the daily cycle of radiated
energy.
NASA Langley Research Center manages the CERES mission.
Langley’s highly successful Earth Radiation Budget Experiment
(ERBE)
provided the foundation for the design of the CERES instrument.
ERBE used three satellites to provide global energy measurements
from 1984 through the 1990s. The TRW Space & Electronics Group
in Redondo Beach, Calif., built all six CERES instruments. (back to the
top)
What CERES Will Measure
CERES will measure the energy at the top of the atmosphere, as
well as estimate energy levels in the atmosphere and at the
Earth’s surface. Using information from very high resolution
cloud imaging instruments on the same spacecraft, CERES also will
determine cloud properties, including altitude, thickness, and the
size of the cloud particles. All of these measurements are critical
for advancing the understanding of the Earth’s total climate
system and the accuracy of climate prediction models. (back to the
top)
Caption: CERES detects low (blue and white) to high (yellow)
amounts of emitted heat.
Balancing the
Earth’s Energy Budget
The balance between Earth’s incoming and outgoing energy
controls daily weather and climate (longterm weather patterns).
Sunlight or solar energy is the planet’s only incoming energy
source. Heat emitted from and sunlight reflected by the
Earth’s surface, atmosphere and clouds make up the
planet’s outgoing energy. Scientists have been working for
decades to understand this critical energy balance, called the
Earth’s "energy budget."
Caption: Earth’s radiation budget is the balance between
incoming and outgoing energy.
The energy received from the Sun is at short wavelengths, while
the energy emitted by the surface of the Earth, the atmosphere and
clouds is at long wavelengths. Greenhouse gases in the atmosphere
absorb the long wavelength energy or heat emitted by the Earth.
Increases in the amounts of greenhouse gases produced by both
natural processes or human activities can lead to a warming of the
Earth’s surface. Such changes may, in turn, alter the
planet’s daily weather and climate. Clouds and small particles
in the atmosphere called aerosols also reflect some sunlight back
into space. Major sources of aerosols include windblown dust,
emissions from the burning of fossil fuels, such as gasoline, and
the burning of forests and agricultural fields. (back to the
top)
Cloud Effects
One of the most intriguing questions facing climate modelers
today is how clouds affect the Earth’s climate and vice versa.
The U.S. Global Change Research Program classifies understanding
the role of clouds and the Earth’s energy budget as one of its
highest scientific priorities. Understanding cloud effects requires
a detailed knowledge of how clouds absorb and reflect sunlight, as
well as how they absorb and re-emit outgoing heat emitted by the
planet. For example, low, thick clouds primarily reflect incoming
solar energy back to space causing cooling. Thin, high clouds,
however, primarily trap outgoing heat and produce warming. To date,
satellite studies have found that clouds have an overall cooling
effect on the Earth.
Analyses of satellite data also indicate that clouds which form
over water are very different from clouds which form over land.
These differences affect the way clouds reflect sunlight back into
space and how much heat emitted from the Earth the clouds absorb
and re-emit. For example, over the equator in the eastern Pacific
Ocean during El
Niño events, there is a significant decrease in the
amount of energy emitted by the Earth due to increased cloudiness.
El Niño events occur when portions of the eastern Pacific
Ocean become considerably warmer than normal, causing an increase
in cloudiness over the region. These changes can affect weather
patterns around the world. (back to the top)
Picture: Cloud Effects on Earth's Radiation
Water Vapor Effects
Water vapor in the atmosphere also impacts our daily weather and
climate, though scientists are only beginning to understand how
this complex mechanism works. Water vapor acts like a greenhouse
gas and absorbs outgoing heat to warm the Earth. Because water
vapor also condenses to make clouds, additional water vapor in the
atmosphere also may increase the amount of clouds. (back to the
top)
Future Missions
One additional CERES instrument is available to fill the gap
between Aqua and the next generation of highly accurate Earth
radiation budget measurements. These observations are expected to
be made on the National Polar-orbiting Operational Environmental
Satellite System (NPOESS) starting around 2010.
To continue the 22-year record of global energy measurements, the
next CERES mission should launch in 2007. (back to the top)
Educational Outreach
As a CERES instrument passes overhead, students worldwide are
observing clouds and then sending their observations to NASA
Langley’s Atmospheric Sciences Data Center (ASDC). At the
ASDC, scientists store data for further analysis by the CERES
science team. The student observations are part of a global
educational outreach program called the Students’ Cloud
Observations On-Line (S’COOL) project. Since the project began
five years ago, S’COOL has reached over 1,000 schools in all
50 states and 57 other countries on five continents. (back to the
top)
Commercial
Applications
CERES supports commercial applications by providing data about
weather and sunlight at the Earth’s surface for the renewable
energy industry via an innovative Web site (http://eosweb.larc.nasa.gov/sse/).
The Surface Meteorology and Solar Energy Project maintains the
site. In the first three years of operation, the number of
registered users of the Web site, including major energy companies,
financial institutions and federal agencies, has grown to over
2,000 from nearly 100 countries. With 35,000 hits per month since
January 2001, SSE is the most accessed Web site at the ASDC. (back to
the top)
For more CERES
information, please contact:
NASA Langley Research Center
Public Affairs Office
Mail Stop 115
Hampton, VA 23681-2199
757-864-6121
www.larc.nasa.gov
Also, see the CERES Home Page:
http://asd-www.larc.nasa.gov/ceres/ASDceres.html
or
NASA Langley’s Atmospheric Sciences Home Page:
http://asd-www.larc.nasa.gov/ASDhomepage.html
(back
to the top)
|
