Clouds and the Earth's Radiant Energy System

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Artist representation of CERES instruments scanning Earth in Rotating Azimuth Plane mode.

Clouds and the Earth's Radiant Energy System (CERES) is on-going NASA climatological experiment from Earth orbit.[1] The CERES are scientific satellite instruments, part of the NASA's Earth Observing System (EOS), designed to measure both solar-reflected and Earth-emitted radiation from the top of the atmosphere (TOA) to the Earth's surface. Cloud properties are determined using simultaneous measurements by other EOS instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS).[2] Results from the CERES and other NASA missions, such as the Earth Radiation Budget Experiment (ERBE),[3] could lead to a better understanding of the role of clouds and the energy cycle in global climate change.[4][5]

Incoming, top-of-atmophere (TOA) shortwave flux radiation, shows energy received from the sun (Jan 26-27, 2012).
Outgoing, longwave flux radiation at the top-of-atmosphere (Jan 26-27, 2012). Heat energy radiated from Earth (in watts per square meter) is shown in shades of yellow, red, blue and white. The brightest-yellow areas are the hottest and are emitting the most energy out to space, while the dark blue areas and the bright white clouds are much colder, emitting the least energy.

Scientific goals[edit]

CERES experiment has four main objectives:

  • Continuation of the ERBE record of radiative fluxes at the top of the atmosphere (TOA) for climate change analysis.
  • Doubling the accuracy of estimates of radiative fluxes at TOA and the Earth's surface.
  • Provide the first long-term global estimates of the radiative fluxes within the Earth's atmosphere.
  • Provide cloud property estimates that are consistent with the radiative fluxes from surface to TOA.

The first CERES instrument (PFM) was launched aboard the NASA Tropical Rainfall Measuring Mission (TRMM) in November 1997 from Japan. However, this instrument failed to operate after 8 months due to an on-board circuit failure. An additional four CERES instruments were launched on the EOS Terra satellite in December 1999 (FM1 and FM2) and on EOS Aqua satellite in May 2002 (FM3 and FM4). A fifth instrument is on the Suomi NPP satellite (FM5). The FM6 instrument is to be launched on the JPPS-1 spacecraft in November 2016. Currently operational are all CERES instruments on Terra and Aqua satellites, and the one on Suomi NPP. Each CERES instrument is a radiometer which has three channels - a shortwave channel to measure reflected sunlight in 0.3 - 5 µm region, a channel to measure Earth-emitted thermal radiation in the 8-12 µm "window" region, and a total channel to measure entire spectrum of outgoing Earth's radiation. CERES spatial resolution at nadir view (equivalent diameter of the footprint) is 10 km for CERES on TRMM, and 20 km for CERES on Terra and Aqua satellites. Onboard calibration sources for channels measuring reflected sunlight include solar diffusers and tungsten lamps. A pair of blackbody cavities that can be controlled at different temperatures are used for the Total and WN channels. Cold space observations and internal calibration are performed during normal Earth scans.

Operating modes[edit]

CERES operates in three scanning modes: across the satellite ground track (cross-track), along the direction of the satellite ground track (along-track), and in a Rotating Azimuth Plane (RAP). In RAP mode, the radiometers scan in elevation as they rotate in azimuth, thus acquiring radiance measurement from a wide range of viewing angles. Until February 2005, on Terra and Aqua satellites one of CERES instruments scanned in cross-track mode while the other was in RAP or along-track mode. The instrument operating in RAP scanning mode took two days of along-track data every month. However the multi-angular CERES data allowed to derive new models which account for anisotropy of the viewed scene, and allow TOA radiative flux retrieval with enhanced precision.[6]

See also[edit]

References[edit]

  1. ^ B.A. Wielicki, et al.; Barkstrom, Bruce R.; Harrison, Edwin F.; Lee Iii, Robert B.; Louis Smith, G.; Cooper, John E. (1996). "Mission to Planet Earth: Role of Clouds and Radiation in Climate". Bull. Amer. Meteorol. Soc. 77 (5): 853–868. Bibcode:1996BAMS...77..853W. doi:10.1175/1520-0477(1996)077<0853:CATERE>2.0.CO;2. 
  2. ^ P. Minnis; et al. (September 2003). "CERES 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. Spain. pp. 37–48. 
  3. ^ B.R. Barkstrom, Bruce R. (1984). "The Earth Radiation Budget Experiment". Bulletin of the American Meteorological Society 65 (11): 1170–1186. Bibcode:1984BAMS...65.1170B. doi:10.1175/1520-0477(1984)065<1170:TERBE>2.0.CO;2. 
  4. ^ B. A. Wielicki, et al.; Harrison, Edwin F.; Cess, Robert D.; King, Michael D.; Randall, David A. (1995). "Mission to Planet Earth: Role of Clouds and Radiation in Climate". Bull. Amer. Meteorol. Soc. 76 (11): 2125–2152. Bibcode:1995BAMS...76.2125W. doi:10.1175/1520-0477(1995)076<2125:MTPERO>2.0.CO;2. 
  5. ^ Geoscience and Remote Sensing Symposium, 1994. IGARSS '94. Surface and Atmospheric Remote Sensing: Technologies, Data Analysis and Interpretation., International. 
  6. ^ N. G. Loeb, et al.; Kato, Seiji; Loukachine, Konstantin; Manalo-Smith, Natividad (2005). "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". J. Atmos. Ocean. Tech. 22 (4): 338–351. Bibcode:2005JAtOT..22..338L. doi:10.1175/JTECH1712.1. 

External links[edit]