No abstract

SUMMARYOn 27 July 1981, as part of the CCOPE experiment, the University of Wyoming King Air research aeroplane made penetrations at six levels ranging from 590mb (-4.9"C) to 770mb (7.2"C) through a nonprecipitating, unglaciated cumulus cloud whose top was at about 560mb (-7°C) and base about 780mb (8°C). The entire flight sequence-from the top downwards-took about six minutes. Principal measurements were of droplet size distribution N ( d ) , number concentration N and liquid water content L , measured at 10Hz (-10m spatial resolution); drop-count N' (50Hz, -2m); temperature T. Also we calculated the fraction F of cloud base air in the mixture sampled ( l H z , -100m). The cloud was substantially subadiabatic throughout the volume studied. Paluch analyses, the observed air motions near cloud top, buoyancy profiles and the observed distribution of L and F with altitude demonstrated that the cloud was diluted principally by entrainment from cloud top. Considerable scatter was found in all microphysical and thermodynamic variables on all spatial scales. Large variations in L were primarily attributable to fluctuations in N and N' . Bimodal spectra were sometimes found at the interface between statistically smooth and highly variable regions. The breadth of the droplet spectra and the size of the largest droplets in the condensate spectrum were not systematically related to the degree of dilution. Calculations showed that a small fraction of the droplets (-100litres-') exhibited superadiabatic growth of up to 4 pm diameter at the intermediate levels, but not near cloud base or cloud top. Support for the idea that droplets in lower concentrations (-10 litre-') grew even faster was provided by 1-D probe measurements of droplets of up to 75 pm diameter in the central and upper regions of the cloud.

No abstract

SUMMARYA passive optical device has been developed for the ground-based in situ measurement of liquid water content, L, in clouds. Light scattered at five, computationally selected, small forward angles is collected andwith the application of appropriate weighting factors -combined to give a response which is linearly proportional to L over the droplet diameter range I to 80pm.L can be measured to within ?0.05gm-' at a frequency of up to 100Hz. thus permitting fluctuations in the liquid water content of clouds to be examined on spatial scales of less than one metre. A miniaturized version of the device -for airborne usage -is under development.

No abstract