Cloud Condensation Nuclei in the Small Cumulus Microphysical Study

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Hudson/Abstract Two research aircraft will be coordinated with the CP-2 dual wavelength radar, which will direct the aircraft to clouds with developing coalescence and will provide a time history of cloud outline and liquid water content. Detailed cloud droplet and drop spectra measurements from the two aircraft will trace the development of coalescence. The two DRI instantaneous CCN (cloud condensation nuclei) spectrometers with calibration equipment will be mounted on the NCAR C-130. At times these two instruments will redundantly monitor the ambient aerosol but for most of the time one spectrometer will monitor the counterflow virtual impactor (CVI) in order to determine the spectrum of nuclei within cloud droplets. This will help ascertain the effect of entrainment on the cloud droplet spectrum and will help differentiate homogeneous, inhomogeneous, and entity mixing processes. Comparisons of the CCN spectra and the spectra of updraft velocities will determine the influence of the aerosol on droplet spectra. This basic cloud forming experiment with comparisons of model predictions of droplet spectra with observations of droplet spectra will yield a better definition of CCN--the important critical supersaturations (Sc). Detailed comparisons of drop (50 Mm) and droplet (50 Mm) spectra will determine the influence of each on the other. The fact that these measurements can be made in time sequence before and after coalescence (before and after the existence of drops) allows cause and effect to be separated with respect to droplet and drop spectra. After coalescence has taken effect the CCN spectra will be affected. SCMS will yield the opportunity to follow in time sequence so that the aerosol can be traced before and after coalescence scavenging has occurred.