Optical properties of shallow tropical cumuli derived from ARM ground-based remote sensing

Herein, the results of a pilot study are presented with analysis of about six months of cloud data. The effective radius r e shows large spatial variability, with the frequency of occurrence relatively narrow near the cloud base, and gradually widening aloft.

Available column data for LWC and r e allow derivation of the pdf of the optical thickness Τ. The pdf shows that clouds with Τ in the range 5 to 10 are most frequent, but there is a long tail with clouds up to Τ = 100. These results are discussed in the context of traditional observations of cloud microstructure using an instrumented aircraft.