Clouds and the Earth's Radiant Energy System

The Clouds and the Earth 's Radiant Energy System ( CERES ) is a climatological experiment of NASA, which is carried out in Earth orbit since January 1998. For CERES scientific instruments are used, which are part of the Earth Observing System of NASA; this measured solar radiation that has been reflected from the earth's atmosphere and radiation, which is radiated from the entire earth's atmosphere. By simultaneous measurements are carried out with other EOS instruments such as MODIS, the properties of clouds can be determined. The results of CERES and other NASA missions such as the Earth Radiation Budget Experiment ( Heritage) will lead to a better understanding of the role of clouds and radiation balance of the Earth with respect to global warming.

Scientific Objectives

The CERES experiment has four main objectives:

  • Continuation of, inter alia, begun using the ERBS ( Earth Radiation Budget Satellite ) in 1984 HERITAGE recording of the radiation flux at the top of the atmosphere to study global warming.
  • Doubling the precision of estimates of the radiant flux at the top of the atmosphere.
  • First-time long-term estimate of the radiation flux within the Earth's atmosphere.
  • Allowing estimates of the characteristics of clouds that are compatible with the radiant fluxes from the surface to the top of the atmosphere.

CERES instruments

The first CERES instrument (PFM ) was launched aboard the NASA Tropical Rainfall Measuring Mission in November 1997 from Japan. Four additional CERES instruments placed on board the Terra satellite in December 1999 ( FM1 and FM2) and on board the Aqua satellite in May 2002 ( FM3 and FM4 ) into Earth orbit. Currently, all CERES instruments of the Terra and Aqua satellites work. Each CERES instrument is a three-channel radiometer: The shortwave channel is intended for the measurement of short-wave solar light in the range of 0.3-5 microns, a channel measures the radiation emitted by the earth heat radiation in the 8-12 micron reaching " atmospheric window " region and a further channel measures the total radiation emitted from the earth.

The spatial resolution of CERES is in nadir direction 10 km for CERES on TRMM and 20 km for CERES on the Terra satellite and aqua. The system has as a solar Bordkalibratoren diffuser, tungsten lamp system with a stability control and a pair of black and hollow body, which can be set to different temperatures.

Observations of the cold room and internal calibrations are performed during normal Earth observations. CERES has been in operation an amazing stability. With 95 % probability of no discernible changes in the sensitivities of some instruments could be detected that were larger than 0.2 %. Floor and All- calibrations are consistent with an accuracy of 0.25%.

Modes

CERES has three operating modes: transverse to the satellite orbit, along the satellite orbit and in the direction of the rotating azimuth plane ( RAP). In RAP mode, the radiometer take in height as they rotate around the azimuth; so that they measure radiation that is received over a wide angle of observation time. By February 2005, the satellite Terra and Aqua scanned in the mode transverse to the satellite orbit, while the others were in the RAP or recording mode along the trajectory. The female in the RAP- mode instrument took a month for two days on even data along its path. The captured from many angles CERES data made ​​it possible to develop new models that take into account the anisotropy of the objects of observation and made ​​it possible to determine the energy fluxes at the top of the atmosphere with improved accuracy.

Digital Object Identifier
194636
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