User:Boomersooner16/sandbox

Influence of Orography (Under the growth section of Formation probably ):

Snowflake growth is sensitive to a number of factors such as the instability of the environment. Mountains and hills play a large role in affecting the instability of clouds by lifting moist air and condensing it into clouds. The type of snowflake produced by these orographic clouds is influenced by a number of factors such as the height of the topography, the shape of the topography, and the synoptic scale conditions (Hobbs et al. 1973). The seeder-feeder effect plays a large role in snowflake growth over mountainous terrain. The seeder feeder effect occurs when a "seeder" cloud aloft precipitates into a lower level "feeder" cloud that is generally orographically produced. Precipitation that falls into the "feeder" cloud acts as seeds for continued growth through deposition or accretion (Schneider). Depending on the phase of the water in the "feeder" cloud, the growth of nuclei in the "feeder" cloud may occur via water vapor deposition or riming in the case of ice crystals. Other factors such as shear-induced turbulence in orographic clouds increase the number of collisions of ice crystals in clouds and therefore increase snowflake growth and therefore snowfall rate (Houze Jr. 2012). The location on a mountain also can affect the type of snowflake falling. More heavily rimed crystals like graupel tend to fall more rapidly and are therefore more likely to fall on the windward slope of a mountain. Lighter, less dense snow that falls slower has a higher chance of being advected to the leeward side of a mountain (Houze Jr. 2012)

These mechanisms as well as others act in conjunction to create what is known as an orographic precipitation gradient. This gradient indicates the relationship between elevation and snowfall totals in a particular region. The distribution of snowfall in complex terrain is strongly influenced by the shape of the topography as well as the synoptic scale conditions. It is difficult for weather models to understand the distribution of snowfall over mountains due to the lack of observations in remote mountainous regions as well as the coarse resolution of weather models.

Notes:

How does orography affect snowflakes?
 * Orography interacts with other environmental factors to produce different snowfall rates in different locations depending on them


 * (Kusunoki et al. 2002) found that there are 4 stages of orographic cloud growth with each preferring a different type and amount of snowflakes
 * The time scale of ice crystal and snowflake growth as well as the spatial steepness of the terrain are very important for the formation and deposition of snowflakes (Hobbs et al. 1973)
 * Seeder-feeder mechanism can lead to increased aggregation of snowflakes as the ice crystals or super-cooled water of cloud aloft fall down into the orographically produced cloud. Here, the feeder cloud can agreggate ice crystals more and create heavier snowfall rates. So where is this process maximized? As you move up in elevation of the windward side of a mountain, riming and graupel become favored over snowflake aggregation which would be favored mid-mountain/bottom of the mountain generally under this mechanism
 * More heavily rimed particles tend to fall on windward side whereas less rimed particles have the chance of being advected to the leeward side, depending on the size of the mountains (Houze Jr. 2012).
 * Shear induced turbulence can act to increase the collisions in ice particles in orographic clouds and increase the snowfall rate (Houze Jr. 2012)
 * The growth, transport, and fallout of ice crystals in orographic clouds is highly dependent on the time-scale of microphysical processes that are often linked to the broader synoptic conditions (Hobbs et al. 1973)