Clouds and the Earth's Radiant Energy System

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False color image of the earth by the CERES instrument of the Terra satellite

The Clouds and the Earth's Radiant Energy System ( CERES ) is a climatological experiment by NASA that has been in orbit since January 1998. Scientific instruments belonging to NASA's Earth Observing System are used for CERES ; these measure solar radiation that has been reflected from the earth's atmosphere and radiation that is radiated from the entire earth's atmosphere. By taking simultaneous measurements 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 (Erbe) will lead to a better understanding of the role of clouds and the Earth's radiation balance in relation to global warming .

Scientific goals

The CERES experiment has four main goals:

  • Continuation of u. a. with the help of the ERBS (Earth Radiation Budget Satellite) started in 1984 ERBE recording of the radiation flux at the top of the atmosphere to study global warming.
  • Doubling the accuracy of estimates of radiation flux at the top of the atmosphere.
  • First long-term estimation of the radiation flux within the earth's atmosphere.
  • Provide estimates of the properties of clouds that are compatible with the radiation fluxes from the surface of the earth to the top of the atmosphere.

CERES instruments

CERES instruments (FM1 and FM2)

The first CERES instrument (PFM) was launched from Japan on board NASA's Tropical Rainfall Measuring Mission in November 1997. Four additional CERES instruments were launched on board the Terra satellite in December 1999 (FM1 and FM2) and on board the Aqua satellite in May 2002 (FM3 and FM4). All CERES instruments on the Terra and Aqua satellites are currently working. Every CERES instrument is a three-channel radiometer : the short-wave channel is intended for measuring short-wave sunlight in the range of 0.3–5 µm , one channel measures the heat radiation emitted by the earth in the “atmospheric window” range, which ranges from 8 to 12 µm and another channel measures all radiation emitted by the earth.

The spatial resolution of CERES in the nadir direction is 10 km for CERES on TRMM and 20 km for CERES on the Terra and Aqua satellites. The system has on-board calibrators such as a solar diffuser, a tungsten lamp system with stability monitoring and a pair of black hollow bodies that can be set to different temperatures.

Cold room observations and internal calibrations are performed during normal earth observations. CERES has shown astonishing stability in operation. There was a 95% probability that no discernible changes in the sensitivity of any instruments could be found that were greater than 0.2%. Soil and All calibrations are consistent with an accuracy of 0.25%.

Operating modes

Artist's impression of the CERES instruments recording the earth in several planes

CERES knows three operating modes: across the satellite orbit, along the satellite orbit and in the direction of the rotating azimuth plane (RAP). In RAP mode, the radiometers record altitude as they rotate around the azimuth; they use it to measure radiation that is recorded over a wide viewing angle. Until February 2005, the Terra and Aqua satellites were scanning across the satellite orbit, while the others were in RAP or recording mode along the orbit. The instrument recording in RAP mode also recorded data along its trajectory for two days every month. The CERES data, recorded from many angles, made it possible to develop new models that take into account the anisotropy of the objects under observation and made it possible to determine the energy flows at the top of the atmosphere with improved accuracy.

Individual evidence

  1. ↑ BA Wielicki et al., Bruce R. Barkstrom, Edwin F. Harrison, Robert B. Lee Iii, G. Louis Smith, John E. Cooper: Mission to Planet Earth: Role of Clouds and Radiation in Climate . In: Bulletin of the American Meteorological Society . 77, 1996, pp. 853-868. doi : 10.1175 / 1520-0477 (1996) 077 <0853: CATERE> 2.0.CO; 2 .
  2. ↑ P. Minnis et al: Cloud Property Retrievals from Imager on TRMM, Terra and Aqua, Proceedings of SPIE 10th International Symposium on Remote Sensing; Conference on Remote Sensing of Clouds and the Atmosphere VII, pp. 37-48, September 2003
  3. ↑ BR Barkstrom: The Earth Radiation Budget Experiment . In: Bulletin of the American Meteorological Society . 65, 1984, pp. 1170-1186. doi : 10.1175 / 1520-0477 (1984) 065 <1170: TERBE> 2.0.CO; 2 .
  4. ↑ BA Wielicki et al., Edwin F. Harrison, Robert D. Cess, Michael D. King, David A. Randall: Mission to Planet Earth: Role of Clouds and Radiation in Climate . In: Bulletin of the American Meteorological Society . 76, 1995, pp. 2125-2152. doi : 10.1175 / 1520-0477 (1995) 076 <2125: MTPERO> 2.0.CO; 2 .
  5. ↑ NG Loeb et al., Seiji Kato, Konstantin Loukachine, Natividad Manalo-Smith: Angular distribution models for top-of-atmosphere radiative flux estimation from the Clouds and the Earth's Radiant Energy System instrument on the Terra Satellite. Part I: Methodology . In: J. Atmos. Ocean. Tech. . 22, 2005, pp. 338-351. doi : 10.1175 / JTECH1712.1 .

Web links

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