Meteorology Ch. 7 notes (precipitation)

What's the most beneficial form of precipitation?

RAIN

What's the least beneficial form of preciptiation?

Hail

What's the most dangerous form of preciptiation?

Freezing rain!!!!

What are Condensation Nuclei?

Particles of dust, dirt, and salt that H2O vapor molecules adhere to ---> cool, condense, form cloud droplets (growth aided by condensation process)

How are condensation nuclei held in the air?

by slow rising currents of air (updrafts)

What happens when a cloud droplet escapes group of condensation nuclei?

it evaporates and doesn't form cloud. :(

What would happen if condensation were the only way to form clouds?

precipitation sized particles like a raindrop would take days!!!

What two methods are in the PRECIPITATION PROCESS?

1) Collision and Coalescence Process (warm cloud process) 2) Bergeron Process (cool cloud process)

What is the Collision & Coalescence Process?

when collisions between cloud drops of different sizes grow rain drops in warm clouds!

What are the two requirements for Collision and Coalescence?

1) must be different sizes of cloud drops 2) must have different fall speeds

How to form rain drops!

large drops overtake small drops to capture them, sometimes large drops break apart

Which drops fall faster?

large drops fall faster than smaller ones!

What factors determine rainfall production?

1) more variety of droplet sizes=more rain 2) cloud thickness 3) more updrafts=more rain 4) high electrical charge=thunderstorm

What about Cumulonimbus clouds makes them efficient producers of precipitation?

lots of moisture, drops of all sizes, strong updrafts, highly charged particles!

What is the Bergeron Process?

cold cloud process where ice crystals grow at the expense of water droplets to produce precipitation

What are clouds called with both ice and water?

"mixed clouds"

Define SUPERCOOLED droplets

water droplets that exist at temps BELOW FREEZING (moving too fast to chill and freeze because too much Energy)

What happens in a mixed cloud?

lots of supercooled droplets get stolen by ice crystals, so the ice crystals become bigger and fall to ground!!

Define Accretion

ice crystals can collide with supercooled drops and cause instant freezing; forms graupel (SNOW PELLETS)

what does graupel do?

falls and collides with ice crystals, fracture, stick to other ice crystals!

Why does rain have an odor?

it pushes earthly gasses into the atmosphere and wind carries ahead of shower!!

Smallest to Largest liquid precipitation?

mist, drizzle, rain

What shape is a droplet?

flat bottom and curved top (because of friction)

Define Virga (LOWER than Fall Streaks)

streaky look below cloud because rain leaves a cloud base but evaporates before reaching the ground (not technically precipitation)

Define Fall Streaks (HIGHER THAN VIRGA)

snow particles (ice crystals) that fall from cirrus clouds and evaporate in the dry air below them

Define Snow

what all precipitation (mostly) starts off as

What determines size and structure of ice crystal?

it's a function of temp at which they form!

What type of snow comes from cold air temps?

since moisture content is small, it makes light fluffy snow with 6-sides crystals

What type of snow forms from warm air temps?

ice crystals clump together into larger bunches

When is there less moisture?

IN COLDER ATMOSPHERE

What's the snow/liquid ratio?

10:1 (larger for drier snowflakes)

Define Sleet

a tiny ice pellet

How does sleet form?

as it falls from cloud, it starts as snowflake then falls into a layer with above freezing temps where it melts into raindrop! then the raindrop falls into a deep freezing layer at surface and REFREEZES INTO ICE PELLET

Define Freezing Rain

rain that instantly freezes upon sub-freezing surface

How does freezing rain form?

as it falls from cloud, it starts as snowflake then falls into a layer with above freezing temps where it melts into raindrop! then the raindrop falls into a shallow freezing layer at surface BUT DOESN'T HAVE TIME TO REFREEZE! when it hits freezing object, it FREEZES INSTANTLY!

Define Flurries

light snow showers that fall for a short time and produce little or no accumulation

Define Showers

light rain (or snow) that falls for a short or random duration (Can start and stop quickly)

Define Blizzard

3 HOURS OR MORE of 1) blowing or drifting snow that reduces visibility to less than 1/4 mile AND 2) frequent gusts of 35 mph or more

Define Hail

pieces of ice, either opaque or transparent, that come from thunderstorms

How does hail form?

large frozen raindrops get pushed back into the upper levels of a THUNDERSTORM due to UPDRAFTS! updraft holds them until critical weight is reached then they fall down

How fast is a 1 inch hail?

49mph

How fast is 1.5 inch hail?

60mph

How fast is 4 inch hail?

100mph

Define Doppler Radar

weather radar that detects and displays areas of precipitation! reflectivity image listens to what signal bounces back and it estimates precipitation image! uses MICROWAVES

Define Tipping Bucket Rain Gauge

2 tiny buckets fill up with .01 inch of rain at a time, tipping back and forth. When each empties, an electronic contact records measurement.