Extended Abstract (392K)P6.8
Long-term Variability of Convective Cloud Visible Albedo from ISCCP Compared to VIRS/MODIS
J. Colleen Mikovitz, SSAI, Hampton, VA; and P. W. Stackhouse, Y. Hu, B. A. Wielicki, S. J. Cox, and S. K. Gupta
The monitoring of satellite visible calibration over long-time periods from satellite to satellite remains a difficult issue, critical to the derivation of long-term cloud and radiation data sets. Most of the work in this area focuses upon using earth targets under clear sky conditions (for a summary see Brest et al., 1997). These calibrations are affected by spectral dependencies of various satellite instruments, surface properties, and atmospheric constituents such as aerosols. Hu et al., (IEEE, 2004) developed a methodology using the coldest-brightest pixels from deep tropical convective cirrus clouds derived from VIRS and MODIS to evaluate the CERES calibration stability. These clouds are relatively homogeneous and optically thick, and occur at a height such that spectrally dependent atmospheric scattering processing are minimized. The frequency of occurrence and microphysical properties of these clouds may change in time without significantly affecting the cloud reflectivity characteristics. Here we adapt the method to evaluate its usefulness for AVHRR and geosynchronous visible channel observations from the International Satellite Cloud Climatology Project (ISCCP) inter-calibrated data set (Rossow and Schiffer, 2000). We compare the variability of the visibility on a per satellite basis for the period from 1984 through 1995 (plans are to extend to 2001 by the time of the conference). Comparisons against VIRS and MODIS visible albedos are made to evaluate the prospect of using this method to connect over 15 years of geosynchronous and polar orbiting observations to EOS era measurement systems. Lastly, the variability in the visible albedos is related to variations in the subsequent ISCCP products and GEWEX Surface Radiation Budget (SRB) radiative flux retrievals.
Poster Session 6, Climatology and Long-Term Studies
Wednesday, 22 September 2004, 2:30 PM-4:30 PM
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