Publication Abstracts

Rossow et al. 1996

Rossow, W.B., C.L. Brest, and M. Roiter, 1996: International Satellite Cloud Climatology Project (ISCCP) Update of Radiance Calibrations. WMO/TD 736. World Climate Research Programme.

The International Satellite Cloud Climatology Project (ISCCP), the first project of the World Climate Research Program (WCRP), was established in 1982 (Schiffer and Rossow 1983) to collect reduced resolution, narrowband (0.6 and 11 µm wavelengths) radiance measurements (Stage B3 data) made by the imaging radiometers on the operational weather satellites (Schiffer and Rossow 1985; Rossow et al. 1987). The primary focus of the first phase (1983-1995) was on the elucidation of the role of clouds in the radiation balance (top of the atmosphere and surface) that determines the climate. In the second phase (1995 onwards), the analysis also concerns improving understanding of the global hydrological cycle in which clouds play a key role. For both purposes, variations of the physical properties of clouds need to be measured with sufficient accuracy to resolve cloud effects over the whole range of scales covered by weather and natural climate variability. The cloud properties are inferred from the satellite-measured radiances which, therefore, must be accurately calibrated.

To obtain global coverage, observations are combined from up to five geostationary satellites (METEOSAT, GMS, GOES-EAST, GOES-WEST and INSAT) and up to two polar orbiting NOAA satellites (only one year of INSAT data have been obtained). The radiometric calibrations of all infrared and visible B3 radiances have been normalized to a common reference standard and the absolute calibration of that standard determined (other wavelengths are collected in the B3 dataset but not re-calibrated). For the first set of cloud products, covering the period from July 1983 through June 1991 (Rossow and Schiffer 1991), the reference standard was the AVHRR on NOAA-7 (Brest and Rossow 1992, Desormeaux et al. 1993, Rossow et al. 1992). The estimated overall uncertainty in the radiance calibrations was ±5-10% for the visible and ±2-3% for infrared (±1.5-2.5K at 300K in brightness temperature).

Several retrospective examinations of the 8-year ISCCP cloud data record have revealed some specific artifacts in the calibration record of the first ISCCP datasets that, although just within the estimated uncertainties, are systematic enough to reduce the quality of the long-term cloud datasets. These quantitatively small problems with the calibration would not have been recognized without examining the whole long-term data record, suggesting that the production of high-quality datasets for climate studies requires an iterative analysis. The decision was made to refine the ISCCP calibration and analysis scheme and to re-process all of the older data, as well as newer data, to produce a homogeneous data record. This document describes the refinements of the calibration procedures implemented to reduce these artifacts, describes a new calibration dataset (Stage BT) now being archived, and provides new calibration tables to replace those given in the previous report on calibration (Rossow et al. 1992).

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BibTeX Citation

  author={Rossow, W. B. and Brest, C. L. and Roiter, M.},
  title={International Satellite Cloud Climatology Project (ISCCP) Update of Radiance Calibrations},
  publisher={World Climate Research Programme},
  address={Geneva, Switzerland},

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RIS Citation

ID  - ro09000a
AU  - Rossow, W. B.
AU  - Brest, C. L.
AU  - Roiter, M.
PY  - 1996
BT  - International Satellite Cloud Climatology Project (ISCCP) Update of Radiance Calibrations
PB  - World Climate Research Programme
CY  - Geneva, Switzerland
ER  -

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