An important and pioneering data product aimed specifically at cloud--climate issues is the International Satellite Cloud Climatology Project (ISCCP) which formerly began in 1983 with the collection of the first internationally coordinated satellite intensity data. This program was the first of its kind and served as a prototype for many other global satellite based projects that have since followed. An extensive amount of data have been processed and the application of these in radiation--climate related research is now blossoming [ Rossow et al., 1993; 1994; Zhang et al. 1994; Tselioudis et al., 1992; Arking and Ziskin, 1994; Soden and Donner, 1994]. This work is also being extended with the development of new cloud information [e.g. Han et al., 1994; Minnis et al., 1993, and others].
There are also other satellite-based projects that provide global information, not only on clouds, but also on aerosol (such as the Clouds from Advanced Very High Resolution Radiometer (AVHRR), and CLAVR (Clouds from AVHRR) [ Stowe et al., 1992]. The availability of satellite microwave radiance data has also provided valuable information about cloud liquid water [ Greenwald et al., 1993, 1995] which is now being contrasted to other cloud products [ Lin and Rossow, 1994], to radiation budget data [ Stephens and Greenwald, 1991b] and to climate models. A key unmet need not only of this research but also of much of the EOS, lies in the suitable validation these global data. Significant contributions to this effort have been realized in the results from process study experiments such as those currently pursued under the Department of Energies Atmospheric Radiation Measurement (ARM) [ Stokes and Schwartz, 1994] program and in past extensive field campaigns such as the First ISCCP Regional Experiment (FIRE), the International Cirrus Experiment (ICE) and the European Cloud and Radiation Experiment (EuCREx).