Weather and Climate: Ch. 5 Flashcards
Billions of minute water droplets and/or ice crystals suspended above surface
Clouds
How does air reach saturation?
- Cooling air to dew point temp (air temp = DPT)
- Cool, unsaturated air passes over a warm body of water
- Surface to condense on
Minute particles in atmosphere:
- Volcanic eruptions
- Wind erosion of soil
- Forest fires
- Ocean spray
- Pollution
Hygroscopic Nuclei:
- Water Seeking (ex: sea salt)
- Condensation at RH < 100%
Who came up with the cloud classification system?
Luke Howard
Stratus (“layer”) =
sheetlike cloud
Cumulus (“heap”) =
puffy cloud
Cirrus (“curl of hair”) =
wispy cloud
Nimbus (“violent rain”) =
rain cloud
What are the 2 criteria for classification of clouds?
Height and Form
Types of cloud height:
- low
- mid
- high
- vertical
Types of cloud form:
- shape
- density
- color
Characteristics of high clouds
- Bases above 20,000’
- Made of ice crystals, thin
- Usually white
Thin, wispy, feathery clouds blown by high winds into long streams, mares’ tales of have a hook
Cirrus (Ci)
Characteristics of Cirrocumulus (Cc)
- Small, white, rounded patches
- Occur individually or in long rows
- Rippel appearance
- “Makerel sky” pattern
- Chicken poppers
Transparent, thin, sheetlike cloud
Cirrostratus (Cs)
Sun and moon clearly shine through ___________ clouds
Cirrostratus (Cs)
Ice crystals in cirrostratus clouds often produce a _____
halo
Ring of light that encircles sun or moon
Halo
What is the base of a middle cloud
6,500’ and 20,000’
What are middle clouds made of?
Ice crystals and water droplets
Large patches of rounded masses or rolls
Altocumulus (Ac)
Usually one part of cloud is darker than the other
Altocumulus (Ac)
If altocumulus clouds appear early on a warm, humid summer morning, there is a good chance of a…
late afternoon (severe) thunderstorm
What cloud is chicken nuggets
Altocumulus (Ac)
Uniform grayish cloud that cover all or large portions of sky
Altostratus (As)
Altostratus clouds are thick so the sun is only ______ visible, referred to as “Watery sun”
dimly
When do altostratus clouds form
often ahead of storms
What kind of precipitation comes from altostratus clouds
widespread and continuous precipitation
What is the base of low clouds?
Below 6500’
Low, lumpy cloud layer that appears in groups or rounded masses
Stratocumulus (Sc)
Blue sky visible between individual clouds
Stratocumulus (Sc)
What cloud is like chicken strips?
Stratocumulus (Sc)
Uniform, white to light gray cloud that blankets entire sky
Stratus (St)
Stratus clouds may produce ________
drizzle
Dark gray, “wet” looking cloud layer associated with rain or snow
Nimbostratus (Ns)
In nimbostratus clouds precipitation tends to be …
light to moderate over long duration
Clouds have bases at low heights and extend into mid and high altitudes
Vertical Development
What are the high clouds?
- Cirrus (Ci)
- Cirrocumulus (Cc)
- Cirrostratus (Cs)
What are the middle clouds?
- Altocumulus (Ac)
- Altostratus (As)
What are the low clouds?
- Stratocumulus (Sc)
- Stratus (St)
- Nimbostratus (Ns)
What are the vertical Development clouds?
- Cumulus (Cu)
- Cumulus Fractus
- Cumulus Congestus (Tcu)
- Cumulonimbus (Cb)
What are the unusual clouds?
- Lenticular
- Pileus
- Mammatus
- Fumulus
- Contrails
- Asperatus
Relatively small puffy clouds that resemble balls of cotton dotting the sky
Cumulus (Cu)
Cumulus clouds have _____ outline with a ______ base
sharp; flat
Cumulus clouds are associated with ____ weather
fair
Cumulus clouds on a fair day:
- Begin forming mid to late morning
- Most extensive mid-afternoon
- Dissipate (vaporize) at sunset
Small cloud fragments broken off from a larger cloud, torn into pieces of cotton candy
Cumulus Fractus
Cumulus Fractus clouds often forming and dissipating ________
rapidly
Cumulus cloud takes on a cauliflower appearance
Cumulus Congestus (Tcu)
Upper portion of Cumulus Congestus clouds are ________ defined
sharply
Cumulonimbus (Cb) is a _________ cloud
thunderstorm
What cloud has a dark, low base to high top (>40,000’)
Cumulonimbus (Cb)
Cumulonimbus clouds produce …
heavy precipitation, hail, lightning, thunder, tornadoes
A cumulonimbus cloud releases tremendous amounts of ______
energy
What is the upper part (anvil) of a cumulonimbus cloud mostly composed of?
ice crystals and fibrous
What does the lower portion of a cumulonimbus cloud consist of?
water droplets
Stationary lens-shaped clouds “UFO cloud”
Lenticular clouds
Where are Lenticular clouds common
mountain areas
Look like pouches hanging from underside of a cloud, resembles a cow’s udder
Mammatus clouds
man-made cloud, form over power plants
fumulus
man-made cloud, Condensation trails that form from aircraft exhaust
contrails
Appears as a rolling, very turbulent, choppy wave cloud
Asperatus
Cloud in contact with ground
fog
Fog restricts visibility to ___ miles or less
0.6
How does fog form?
- Cooling (air cooled below dew point (saturation point))
- By evaporation and mixing
Forms on clear night with high RH and light winds
Radiation (ground) fog
Characteristics of Radiation (ground) fog
- high pressure
- thickest in low-lying areas
- dissipates 1-3 hours after sunrise
Warm air mass passes over a cold surface and is chilled
Advection Fog
Characteristics of Advection Fog
- persist for long periods of time
- snow-covered ground
- cold surface of lake or ocean (Pacific Coast)
Forms on mountain slopes due to upslope movement of humid air
Upslope Fog
When does Steam Fog develop
on a cold day
Cold and dry air flows over a warm body of water
Steam Fog
Appears as rising streamers that resemble steam
Steam Fog
Steam Fog may form above a ___ surface on a sunny day
wet
What is an example of steam fog
your breath in winter
Warm, humid air is forced to rise over cooler, dryer air
Frontal fog
Precipitation fog
Frontal fog
Where does frontal fog form
along frontal boundaries
Tiny droplets of water
Dew
Water vapor condenses on a cold surface
Dew
Dew freezes after forming
White (frozen) dew
Dew forms on a _____, _____ night (high pressure)
clear, calm
When does frost form?
when dew point temp is below 32℉ and high pressure
Cold occurs over a widespread area for a long time
Frost/Freeze Hazard
Frost Advisory =
< 32℉
Hard Freeze Warning
< 28℉