Multi-Instrument Comparison of Top-of-Atmosphere Reflected Solar Radiation

Observations from the Clouds and the Earth's Radiant Energy System (CERES), Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) between 2000 and 2005 are analyzed in order to determine if these d...

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Bibliographic Details
Published in:Journal of climate 2007-02, Vol.20 (3), p.575-591
Main Authors: Loeb, Norman G., Wielicki, Bruce A., Su, Wenying, Loukachine, Konstantin, Sun, Wenbo, Wong, Takmeng, Priestley, Kory J., Matthews, Grant, Miller, Walter F., Davies, R.
Format: Article
Language:English
Subjects:
Atmosphere
Calibration
Ceres
Climate change
Clouds
Comparative studies
Earth, ocean, space
Exact sciences and technology
External geophysics
Fall lines
Geophysics. Techniques, methods, instrumentation and models
Infrared radiation
Marine
Meteorology
Nadir
Oceans
Photosynthetically active radiation
Radiance
Radiative transfer. Solar radiation
Satellites
Solar energy
Standard deviation
Tropical regions
Ultraviolet radiation
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Summary:Observations from the Clouds and the Earth's Radiant Energy System (CERES), Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) between 2000 and 2005 are analyzed in order to determine if these data are meeting climate accuracy goals recently established by the climate community. The focus is primarily on top-of-atmosphere (TOA) reflected solar radiances and radiative fluxes. Direct comparisons of nadir radiances from CERES, MODIS, and MISR aboard theTerrasatellite reveal that the measurements from these instruments exhibit a year-to-year relative stability of better than 1%, with no systematic change with time. By comparison, the climate requirement for the stability of visible radiometer measurements is 1% decade-1. When tropical ocean monthly anomalies in shortwave (SW) TOA radiative fluxes from CERES onTerraare compared with anomalies in Photosynthetically Active Radiation (PAR) from SeaWiFS—an instrument whose radiance stability is better than 0.07% during its first six years in orbit—the two are strongly anticorrelated. After scaling the SeaWiFS anomalies by a constant factor given by the slope of the regression line fit between CERES and SeaWiFS anomalies, the standard deviation in the difference between monthly anomalies from the two records is only 0.2 W m-2, and the difference in their trend lines is only 0.02 ± 0.3W m-2decade-1, approximately within the 0.3 W m-2decade-1stability requirement for climate accuracy. For both the Tropics and globe, CERESTerraSW TOA fluxes show no trend between March 2000 and June 2005. Significant differences are found between SW TOA flux trends from CERESTerraand CERESAquabetween August 2002 and March 2005. This discrepancy is due to uncertainties in the adjustment factors used to account for degradation of the CERESAquaoptics during hemispheric scan mode operations. Comparisons of SW TOA flux between CERESTerraand the International Satellite Cloud Climatology Project (ISCCP) radiative flux profile dataset (FD) RadFlux product show good agreement in monthly anomalies between January 2002 and December 2004, and poor agreement prior to this period. Commonly used statistical tools applied to the CERESTerradata reveal that in order to detect a statistically significant trend of magnitude 0.3 W m-2decade-1in global SW TOA flux, approximately 10 to 15 yr of data are needed. This assumes that CERESTerrainstrument calibratio
ISSN:0894-8755
1520-0442
DOI:10.1175/jcli4018.1