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U. Katz and W. C. Kocmond

Abstract

The activation supersaturation of several artifically prepared NaCl aerosols was measured in the laboratory using a thermal gradient diffusion chamber. Size distributions of these aerosols and total particulate concentrations were determined with a Whitby Aerosol Analyzer and a Gardner Small Particle Detector. From a combination of these data, the relationship was derived between supersaturation and necessary minimum size of the particles for nucleation. This experimentally obtained correlation indicates that, at a given supersaturation, a NaCl particle, has to be two to three times larger than theory predicts in order to be active as a cloud condensation nucleus. Possible explanations for the discrepancy are discussed.

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R. J. Pilié, E. J. Mack, C. W. Rogers, U. Katz, and W. C. Kocmond

Abstract

This paper summarizes the results of seven field expeditions aboard the Naval Postgraduate School's R/V Acania, designed specifically to study the formation of marine fog along the California coast. On the basis of observations and analyses, physical models have been formulated for the formation and persistence of at least four different types of marine fog which occur off the West Coast: 1) fog triggered by instability and mixing over warm water patches; 2) fog developed as a result of lowering (thickening) stratus clouds; 3) fog associated with low-level mesoscale convergence; and 4) coastal radiation fog advected to sea via nocturnal land breezes. In addition, it has been found that the triggering of embryonic fogs and further downwind development produces a synoptic-scale fog-stratus system and is responsible for redevelopment of the unstable marine boundary layer after Santa Ana events.

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