Recorded presentation2.1
Climate calibration of the ISCCP visible imagers
Laura M. Hinkelman, JISAO/Univ. of Washington, Seattle, WA; and C. Bishop, D. R. Doelling, S. Kato, J. C. Mikovitz, W. B. Rossow, P. W. Stackhouse, T. C. Stone, and B. A. Wielicki
Although the International Satellite Cloud Climatology Project (ISCCP) was not originally conceived of as a source of climate data, it has been frequently used as such because of its long period of coverage. A recent interagency report summarized the calibration stability requirements as 0.6% per decade to restrict uncertainty in low cloud feedback for a 50% uncertainty in cloud feedback, and 0.3% per decade for a 25% uncertainty. These strict requirements are well below the initial ISCCP estimated stability levels of 3 to 5% for visible channels. However, several NASA Earth Observing System (EOS) developments have shown a capability to greatly improve the calibration of the ISCCP cloud and related SRB radiation records from 1983 to present. CERES developed two new capabilities; a) the use of the optically thick limit deep convective clouds as a reflectivity target at the bright end of the radiance detectors, and b) use of broadband stable radiometers to improve the stability of narrowband imager data such as geostationary data. In a related activity, NASA EOS funded the USGS led ROLO program to use surface based lunar observations to characterize the spectral, phase angle, and libration dependence of sunlight reflected from the lunar surface. SeaWiFS has demonstrated the use of such lunar observations to achieve exceptional (~0.1%) stability in narrowband imager channels. Recently, a new project has been funded to apply these techniques retroactively to ISCCP imager data. This activity has the potential to improve the ISCCP radiances to climate data requirements, which would greatly enhance the usefulness of the ISCCP and SRB data sets for climate change studies. This poster presents the fundamentals of the new techniques and early results of their application to ISCCP radiances from geostationary and AVHRR satellites.
Session 2, Climate Monitoring and Studies—II
Thursday, 15 January 2009, 11:00 AM-12:15 PM, Room 126BC
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