Three cloud types defined by the ISCCP C product are used: deep cloud
combined with CsCc (cloud type 1), cirrus (cloud type 2), and stratus
(cloud type 3).
CsCc linearly depends on deep cloud, so we combine them to
be one cloud type. Cloud type 1 linearly depends on large-scale
precipitation with the coefficient:
In the current version, cirrus and stratus are observed seasonal climatology from the ISCCP C2 data. For more details, see Section 2.2 in Zeng et al. [2].