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24 terms

Precipitation

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What role does the curvature effect play in droplet formation?
It is easier for water molecules to evaporate from a curved surface, and smaller droplets will have more evaporation that takes place. Condensation will not be able to keep up with evaporation, therefore saturation will not be maintained
What role does the solute effect play in droplet formation?
An inseparable solution forms between water and nuclei, binding the water molecules from evaporating, thus small droplets will no longer evaporate. This allows vapor molecules to attach themselves at a faster rate than they leave causing the droplet to grow.
What are the two precipitation processes?
Collision-coalescence & ice crystal process
What is the collision-coalescence process?
"warm rain" process, droplets will collide to increase in size, but if there is no size difference between droplets, they will not combine
What is the ice crystal process?
The difference in vapor pressure causes the vapor molecules to diffuse to the ice, this reduces the vapor pressure over the droplet (which is out of equillibrium). Therefore, it evaporates to replenish the deficit in water vapor, and the ice crystal grows by deposition
What is supercooled water?
Water at temperatures below freezing
What are the 5 types of precipitation?
Sleet, freezing rain, snow, rain, and hail
What is the temperature profile for sleet?
Starts as snow, turns to rain, then has a deep freezing layer
What is the temperature profile for freezing rain?
Starts as snow, turns to rain, then has a shallow freezing layer
What is the temperature profile for snow?
Starts as snow and falls all the way to earth and does not unfreeze
What is the temperature profile for rain?
Starts as snow, unfreezes as it falls to the earth, does not re-freeze
What are the different ways that ice crystals can grow?
accretion (riming), multiplication, and aggregation
What is accretion (riming)?
when supercooled drops freeze on contace with falling ice crystals. If it is heavy, snow pellets (graupel) may form
What is multiplication?
colliding and shattering of ice crystals producing many more ice crystals that will grow, fall, and shatter
Aggregation
When temperatures are closer to freezing near the surface, collisions between ice crystals will cause them to stick together
What determines that shapes of ice crystals?
the temperature and amount of moisture available
What process makes a snowflake look "full" or "fat"?
Accretion (riming)
What process makes a snowflake look like shrapnel?
Multiplication
What process makes a snowflake look like "common" snowflake?
Aggregation
What makes a favorable environment for hail?
Width and tilt of updraft, with best trajectory being horizontally through the cloud
What is the snow to liquid ratio?
The ratio of snow to liquid equivalent, needed to forecast snowfall
The process that occurs when supercooled drops freeze on contact with falling ice crystals is what?
Accretion (riming)
The process that occurs when temperatures are close to freezing and ice crystals collide sticking together is called what?
Aggregation
The process that occurs when ice crystals of different shapes and degrees fall at different speeds, collide and shatter is called what?
Multiplication