The pressure in a cell profile which corresponds to the cloud top temperature. Cloud with top above 440 mb. The fractional area of opaque cloud which, radiating as a black body at the cloud top temperature, would account for the channel 8 cloud forcing for those pixels within the cell which are not reporting the presence of cloud in a higher category. The transmittance for such pixels is unity minus the effective cloud fraction. This relationship between transmittance and effective cloud fraction still holds for thin clouds with no discernible gaps.
Guide is more complex.
A determination from the satellite data set of which individual pixels within a scene are probably clear sky, as opposed to partially or completely contaminated by cloud. Since clear sky is itself a relative term, this determination is somewhat arbitrary and is subject to errors of both exclusion and inclusion. Systematic errors in the cloud mask will be reflected to some extent in the reported clear sky radiances for a cell, and hence in the inferred cloud forcing and in the cloud analysis, and users should be sensitive to this possibility. An intermediate product in determining the cloud mask, representative of the distribution over different, apparently clear, areas within a cell of the temperature of the underlying land or water surface. There is no absolute standard for measuring the accuracy of the reported variables in this product.