AOSC 200 Lecture 14: Lecture 14_ Precipitation
29 Mar 2018
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Document Summary
Homogeneous of spontaneous nucleation formation of a pure water droplet by condensation from supersaturated vapor without aerosols. Hygroscopic nuclei are water seeking, and water vapor rapidly condense on their surfaces. Hydrophobic nuclei are water repelling and resist condensation. A cloud droplet rising then falling through a warm cumulus cloud can grow by collision and coalescence and emerge from the clouds as a large raindrop. There are many material and substances which act as nucleates, each promotes freezing at a specific temperature or nucleation temperature. They are generally categorized as high temperature (silver iodide, dry ice and ice nucleating proteins) or low temperature (calcium, magnesium, dust and silt nucleates) It is the low-temperature nucleators that are found in large numbers in untreated snowmaking water. The nucleation temperature of snowmaking water is between 15 f and 20 f) Inject cloud with small particles that act as condensation nuclei, starting the precipitation process. Need clouds: seeding does not generate clouds.
