Weather and Climate: Ch. 16 Flashcards
A whitish ring of light surrounding the sun or moon
Halo
Ice crystals in cirrostratus clouds refract the sun’s rays
Halo
Light is concentrated on either side of the sun as two brilliant spots
Sundogs
Vertical streaks of light that appear above and below a low sun as it shines through ice-crystal clouds
Sun Pillars
An arch-shaped array of colored bands
Rainbows
To see a rainbow, you must be facing the ____ with ____ at your back
rain; sun
Order of Rainbow colors from outer to inner most band:
red, orange, yellow, green, blue, indigo, and violet
Appears as a bright whitish disk centered on the moon
Corona
Bright area produced by diffraction
Iridescence
Adequate for outdoor activities without the need for artificial lighting
Civil twilight
Sufficient to distinguish outlines of objects on the ground
Nautical Twilight
Occurs when sun’s disc is between 12° and 18° below horizon
Astronomical Twilight
For clouds to precipitate:
Cloud particles must grow large enough to overcome updrafts
____ has the greatest ability to overcome an updraft
Hail
water droplets that remain liquid when temps below freezing
Supercooled drops
Warm clouds =
above freezing temps at all levels
Characteristics of warm clouds
- Boundaries sharply defined
- Common in tropics
Cold clouds =
made of ice crystals and/or supercooled drops in temps below freezing
Characteristics of cold clouds
- Wispy
- Important rain producers in midlatitudes
What are the two precipitation processess
- Collision-Coalescence Process
- Bergeron-Findeisen Process
Characteristics of Collision-Coalescence Process
- Warm cloud
- Droplets of different sizes collide and coalesce into larger droplets
- Important in tropics
Characteristics of Bergeron-Findeisen Process
- Ice-crystal process
- Cold cloud
- Ice crystals grow at expense of supercooled water droplets
- May grow large enough to fall as snowflakes
- If snowflakes melt before reaching ground, they fall as raindrops
Much of rain falling in midlatitudes in summer begins as _____
snow
Drops of liquid water
Rain
___ __________ causes raindrops to fall as slightly flattened spheres, diameters at least ____ mm
Air resistance; 0.5
Fine, uniform drops of water
Drizzle
What is the diameter of drops of water in a drizzle?
0.02’’
Drizzle drift very _____ to surface
slowly
Where does a drizzle originate?
stratus or nimbostratus clouds
Smallest droplets able to reach ground
Mist
What does mist closely resemble?
Fog
Streaks of precipitation falling from a cloud
Virga
In virga, water ________ before reaching surface
evaporates
Ice crystals that sublimate when they enter dry air, wisps
Fallstreaks
Intermittent precipitation from cumuliform cloud
Shower
Aggregates of ice crystals in form of flakes
Snow
Showers are usually _______, but _______ in duration (cloudburst)
short; heavy
Snow ____ in shape and size
vary
The shape and size of a snowflake depends on …
water vapor concentration and temp
When are snowflakes small?
At very low temps and water vapor is low
When do snowflakes stick together?
At air temps near or slightly above freezing (diameters 2 to 4’’)
Light showers that fall for short durations and produce light accumulations
Flurries
Soft, oblong ice pellet
Graupel (“soft hail”)
Falling or blowing snow that reduces visibility to 0.25 mile or less for at least 3 hours
Blizzard Warning
What are wind speeds at for at least 3 hours during a blizzard Warning?
25 mph
Where are blizzards most common?
eastern CO north into SD, ND, MN
Clear to translucent ice pellets
Sleet
What season does sleet occur?
winter
Sleet refreezes into ice particles _____ to striking ground
prior
Sleet ______ when it hits the ground
bounces
Rain (or drizzle) that freezes on contact with cold surface
Freezing Rain (glaze)
Freezing rain forms a coating of ice (glaze) on _______ surfaces
exposed
Hard, round pellets or irregular lumps of ice
Hail
What is the diameter of hail?
0.20’’ or more
Hail is characterized by alternating layers of _______ and ______ ice
opaque and clear
How does hail develop?
Within intense updrafts of cumulonimbus clouds
Hail is usually a _______ or ________ event
spring or summer
What is the size of hail?
pea size to size of orange or larger
Hailstones that cover landscape in long, narrow strip
Hailstreak (hail swath)
Where is hail most likely in North America?
Western Great Plains
Ice accumulations of at least 0.25’’
Ice Storm Warning
Ice Storm can be highly ________ and ________
localized and persistent