A detailed analysis of several versions of the Caltech Active Strand C
loudwater Collector (CASCC) is conducted. Efficiency calculations, des
ign considerations and procedures for cloud liquid water content estim
ation from the collection rates of these instruments are discussed. Th
e size-fractionating CASCC is capable of simultaneous collection of sa
mples representing two portions of the cloud drop size spectrum. Large
drops are collected in an inlet stage while smaller drops are collect
ed in a second stage. Theoretical calculations, which assume no aerody
namic interaction between adjacent rows of collection rods in the inle
t, suggest the inlet should have a 50% size cut corresponding to a dro
p size of 23 mu m diameter. However, field test results suggest that f
ocusing of the flow passing through a row of cylinders may increase th
e efficiency of collection on the subsequent cylinder row, thereby dec
reasing the overall size cut for the inlet. The CASCC2, a compact vers
ion of the original CASCC, is designed to sample the entire cloud drop
spectrum. Comparison of the cloudwater collection rates of the CASCC2
and the size-fractionating CASCC showed good agreement when normalize
d by the flow rare through each collector. The Caltech Heated Rod Clou
dwater Collector (CHRCC), designed for use in supercooled clouds, feat
ures a theoretical 50% lower size cut corresponding to a drop diameter
of 9 mu m. Liquid water content values estimated from the CHRCC cloud
water collection rates correlated reasonably well with values measured
with a Gerber Particle Volume Monitor (PVM-100) in both warm (r(2) =
0.83) and supercooled (r(2) = 0.71) cloud conditions.