Thursday, 6 June 2002
Effective cloud fractions for broken water cloud fields accounting for cloud transmission
Since the solution for a particular broken cloud field is not particularly useful for evaluating cloud effects on the GCM space scale, parameterizations can be quite useful. One parameterization for broken cloud fields is the effective cloud fraction. For that reason, is common to parameterize the cloud effects by using an effective cloud fraction. Previous has work has shown that effective cloud fractions derived using the assumption of black clouds is quite effective for wet/opaque water cloud fields. Recently, cloud measurements provided by ARM instruments have extended to drier/transparent water cloud fields.
In this study, we combine measurements from several different instruments such as the cloud radar, pyrgeometer, microwave radiometer, and the AERI to determine both the absolute cloud amounts and the effective cloud fractions while accounting for partial cloud transparency. In this way, the accuracy of the effective cloud parameterizations can be determined by comparing the parameterized effective cloud fraction to the effective cloud fraction derived from measurements.