types of precipitation precipitation comes in two forms precipitation comes in two forms liquid –...
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Types of PrecipitationTypes of Precipitation Precipitation comes in two formsPrecipitation comes in two forms
Liquid – rain, drizzleLiquid – rain, drizzle Solid - Solid - freezing rain or drizzlefreezing rain or drizzle
snowsnow sleet or ice pelletssleet or ice pellets snow pellets or graupelsnow pellets or graupel snow grainssnow grains hailhail
The vertical temperature structure of the The vertical temperature structure of the atmosphere determines whether liquid or solid atmosphere determines whether liquid or solid precipitation will fall.precipitation will fall.
RainRain
►Liquid drops with a diameter of 0.5 Liquid drops with a diameter of 0.5 mm or moremm or more
►Most rain begins as snow high in the Most rain begins as snow high in the atmosphere that melts in the warmer atmosphere that melts in the warmer air of the lower atmosphere to fall as air of the lower atmosphere to fall as rain.rain.
Rain IntensityRain Intensity
Very Light: widely spaced drops do not widely spaced drops do not completely wet groundcompletely wet ground
Light: produces trace to 0.10 inches/hour: produces trace to 0.10 inches/hour
Moderate: produces 0.11 – 0.30 : produces 0.11 – 0.30 inches/hourinches/hour
Heavy: produces over 0.30 inches/hour: produces over 0.30 inches/hour
DrizzleDrizzle
►precipitation in the form of liquid drops precipitation in the form of liquid drops with diameters less than 0.5 mmwith diameters less than 0.5 mm
►reduces visibility more than light rain reduces visibility more than light rain because there are many more drops in because there are many more drops in a shower of drizzle than in a shower of a shower of drizzle than in a shower of light rainlight rain
Drizzle and RainDrizzle and Rain
Heavy Drizzle vs. Heavy RainHeavy Drizzle vs. Heavy Rain
QuestionQuestion
►How are amounts of rain classified?How are amounts of rain classified? A. visibility limitsA. visibility limits B. inches per hourB. inches per hour C. centimeters per hourC. centimeters per hour
Freezing Rain or Freezing Freezing Rain or Freezing DrizzleDrizzle
liquid drops that fall into a layer liquid drops that fall into a layer of below freezing air close to the of below freezing air close to the ground and freeze on contactground and freeze on contact
glaze surfaces with a coating of glaze surfaces with a coating of iceice
Freezing Rain
Why is freezing rain so dangerous?
SNOW
solid white or translucent ice crystals mainly branching in hexagonal forms
most precipitation forms as snow
Snowfall Intensity
Very Light: Scattered flakes do not completely wet or cover the ground
Light: visibility is 5/8 of a mile or more
Moderate: visibility is less than 5/8 mile but not less than 5/16 of a mile
Heavy: visibility is less than 5/16 of a mile
Snow
Heavy snow
Sleet or Ice PelletSleet or Ice Pellet
• sleet consists of transparent or translucent pellets of ice less than 5mm in diameter
• usually sleet is spherical
• formed when snow falls through above freezing and then below freezing layers of air
• pellets bounce off of surfaces on contact
Sleet
Snow Pellets or Graupel
white, opaque, nearly round ice particles similar to snow in structure
formed when ice crystal falls through layers of water droplets that stick together to make it larger
ranges in size from 2 to 5 mm in diameter often falls in a shower before or with snow
when surface temperatures are very near freezing
Small Graupel
Graupel
Snow Grains
very small, white, opaque particles of ice solid equivalent of drizzle and resemble snow
pellets in appearance but with diameters less than 1 mm
never fall in shower fall in small quantities from stratus clouds or
from fog
HAILHAIL
►round or irregular lumps of ice round or irregular lumps of ice produced by convective clouds produced by convective clouds (cumulonimbus)(cumulonimbus)
►hail has diameter greater than 5 mmhail has diameter greater than 5 mm►can reach size of grapefruitscan reach size of grapefruits►cause significant damage to propertycause significant damage to property
Hail DamageHail Damage
How Hail FormsHow Hail Forms
► in thunderstorms that have tremendous in thunderstorms that have tremendous updrafts and down draftsupdrafts and down drafts
►hailstones begin as tiny ice crystals hailstones begin as tiny ice crystals that grow in size by accretion (adding that grow in size by accretion (adding layer after layer of ice) as they are layer after layer of ice) as they are thrown into water droplets in the stormthrown into water droplets in the storm
►storm updrafts suspend hailstones until storm updrafts suspend hailstones until they are too large and fallthey are too large and fall
Hail FormationHail Formation
Huge Hail
Hail Damage
