Cloud Statistics from Spaceborne Lidar Systems - Earth Science: New Methods and Studies - page 32

surface observations (Warren et al., 1985) that provide an estimate of the percentage of
low level clouds without any cloud above to be about 40%. Winker et al. (1998) show
about the same CPDF as that retrieved from the local method.
Figure 5. Cloud top height probability density functions (Figure 5a) and cumulative PDF (CPDF)
(Figure 5b) for all the cloud structure established from LITE, and CALIOP at the same date as for
Figure 4a and b.
When the upper cloud structure is semitransparent, the lidars offer the possibility
of identifying lower-level scattering layers. The effi ciency of lower scattering layer
detection is directly linked to the SNR. Figure 5a and b gives the PDF (CPDF) for
all the cloud structures for each spaceborne lidar. They are similar for GLAS and
CALIPSO with a slight increase of middle-altitude clouds. The difference is more
important for LITE where more low level cloud structures are detected. In this last
case, the CPDF reach about the same value (~45%) at an altitude of approximately 6 km.