Chapter 7 meteorology

processes that would be relevant in a warm stratus cloud

Coalescence and Collision

processes could happen in the mixed phase region of a cumulonimbus cloud?

Accretion, Collision, and Aggregation

refers to two ice crystals merging together.

aggregation

efers to two particles, whether liquid or ice, hitting each other, but not necessarily sticking together.

collision

What type of precipitation falls through cold air (<0°C), then a melting layer, then a shallow freezing layer, hitting the ground without having time to refreeze?

freezing rain

type of precipitation results from numerous rounds of accretion, growing in size, until it is heavy enough to fall through the updraft?

hail

type of precipitation falls through cold air (<0°C) the entire time and reaches the ground as ice?

snow

type of precipitation falls through warm air and reaches the ground as liquid water?

rain

What is hail size directly correlated with?

updraft strength

What is the beginning reflectivity level commonly used to indicate the possibility of hail within a thunderstorm?

what color is hail when the hailstone is in abovee freezing temps?

clear

what color is hail when its in below freezing temps

opaque

what size hail is considered severe?

greater than 1 inch

what are some seeding agents?

Dry ice, silver iodide, and any chemical structure that is similar to ice.

what is cloud seeding

using any seeding material to use more of the supercooled water and helps it become large enough to fall to the ground.

natural cloud seeding

cirrus clouds drop ice crystals, seeding supercooled liquid clouds below.

what temp does it need to be for water droplets to freeze in clouds or for spontaneous freezing?

-40 degrees C

deposition nuclei

goes straight to ice crystal, skipping the liquid phase.

freezing nuclei

acts like freezing rain, nuclei have to be immersed in the drop before freezing.

contact nuclei

water that freezes on contact, freezing rain

what is Rime?

When supercooled cloud or fog droplets freeze on contact, they form an accumulation of white granular ice called rime.

what does rain start as in the middle and northern lattitudes?

snow, even in the summer.

what is the most common seen snowflake

dendrite

what cloud do snow grains typically come from?

stratus

what cloud do snow pellets typically come from?

cumulus congestus

what size are snow pellets

2-5 mm

what size are snow grains

less than 1 mm

how much dry snow is in one inch of water?

20 inches

how much wet snow is in 1 in of water.

6 inches

what is virga

rain or drizzle that evaporates before reaching the ground

rain water drop size

greater than 0.5 mm

drizzle water drop size

less than 0.5 mm

down burst

a rain shower that is excessively heavy

rain shower

a brief sporadic rain event

what is classified as heavy snow

4 inches in 12 hours, 6 inches in 24 hours

how are flurries classified

light showers of light dusting snow.

snow squall

a rain shower but with snow.

what vis is considered light snow

greater than 1 ½ mile of visibility

what vis is considered moderate snow

greater than ¼ mile but less than or equal to ½ mile

what vis is considered heavy snow

less than or equal to ¼ mile

what part of the cloud do snowflakes tend to form

relatively warmer portions, -15 degrees C

what effects the size of rain droplets

thickness of clouds and strength of updraft.

what is terminal velocity?

the speed at which raindrops fall

what is the TV of tiny cloud droplets?

0.1 m/s

what is the TV for larger droplets?

6.5 m/s

are cloud droplets bigger than water droplets

no, cloud droplets are much smaller

what do clouds need in order to form cloud droplets

CCNs (dust, salt, aerosols)

which radar product shows the intensity of a thunderstorm

base reflectivity

which radar product shows the direction a thunderstorm is moving

base/radial velocity

what are the two modes of base reflectivity imagery

clear and precipitation

what is the most common tilt of base reflectivity

0.5 degrees

what dBZ level should be concerned about the presence of hail

60 dBZ

which type of precipitation is more centralized and is more intense?

convective

which type of precipitation is more spread out and less intense?

Stratiform

TVS

Tornado Vortex Signature

ice particle collide and stick together, makes snowflakes

aggregation

Accretion

supercooled water freezes on contact with ice falling, hail

Collision

ice crystals or water drops colliding with each other making a bunch of smaller crystals or rain drops.

coalescence

two liquid particles colliding making larger droplets

what causes hail to grow larger

stronger updraft