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Last modified
7/28/2009 2:29:18 PM
Creation date
7/18/2007 11:59:27 AM
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Template:
Weather Modification
Title
Western Kansas Weather Modification Program 2006 - Final Report
Prepared By
Walter E. Geiger III
Date
10/30/2006
State
KS
Weather Modification - Doc Type
Report
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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />II. THE PHYSICAL BASIS FOR CLOUD SEEDING <br /> <br />Although a vast amount of knowledge is known generally about clouds, there is still <br />much unknown about those rapidly growing convective (thunderstorm) clouds which can quickly <br />become severe, produce highly destructive hail and surface winds, cause flooding, deadly <br />lightning and produce occasional tornadoes. The following is a simplified explanation of how <br />convective clouds grow to become severe storms as well as the general theory supporting the <br />feasibility of seeding to reduce hail and/or to increase rainfall. <br /> <br />A convective cloud forms when rising air containing water vapor cools by adiabatic <br />expansion reaching a temperature at which condensation occurs to form water droplets. <br />Condensation begins first upon the relatively abundant microscopic atmospheric aerosols, or <br />particles, called cloud condensation nuclei (CCN) and include dust, smoke and salt particles. <br />Clouds become visible when a collection of water droplets have grown to sufficient size. The <br />primary mechanisms in Western Kansas causing air to rise and form into convective clouds are: <br /> <br />(I) surface heating <br /> <br />(2) advancing cold and warm frontal systems <br /> <br />(3) relatively cold air in the upper atmosphere sinking into warmer air ahead of it causing warm, <br />moist air to be displaced upward <br /> <br />(4) upslope air flow moving moisture from lower altitudes in Eastern Kansas into higher altitude <br />areas of West em Kansas and Eastern Colorado, usually a post-frontal condition <br /> <br />(5) regions of horizontal convergence created by troughing at the earth's surface, or aloft <br /> <br />(6) Elevated convection---or at least one form of it <br /> <br />(7) upper level low pressure systems (most often associated with low-level convergence, sinking <br />cold air and/or upslope effects) <br /> <br />(8) convective scale interaction resulting from thunderstorm outflows digging under warm, <br />humid air, often forcing a rapid lifting above it into a more unstable atmosphere <br /> <br />(9) gravity waves---very small, internal perturbations traveling through the atmosphere, many of <br />which are created randomly and not easily detectable in real-time. Such waves act much like the <br />effects seen from convective scale interaction. <br /> <br />There is also another atmospheric aerosol present in the atmosphere, termed ice nuclei <br />(IN). These are particles upon which, if found in condensed water droplets, enhance water <br />droplet freezing. Ice crystals also may form upon IN directly from water vapor. Despite the <br />abundance of CCN, there is a relative scarcity of IN found in most naturally occurring <br />convective clouds. This fundamental lack of sufficient numbers of IN causes clouds to fail to <br /> <br />3 <br />
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