chap5 Flashcards
a rising parcel of air
expands and cools
a sinking parcel
compresses and warms
If a parcel of air expands and cools, or compresses and
warms, with no interchange of heat with its outside
surroundings, this situation is called
adiabatic process
the rate of adiabatic cooling or warming remains constant and
is about
10°C for every 1000 meters
As the rising air cools, its relative humidity
increases as the air temperature approaches the
dew-point temperature.
If the rising air cools to
its dew-point temperature
the relative humidity becomes 100 percent.
Further lifting results in condensation, a cloud forms, and ________ is released into the rising air.
latent heat
Unlike the dry adiabatic rate, the moist adiabatic rate is not
constant, but varies greatly with ___________ and __________
temperature and moisture content
TRUE OR FALSE: warm saturated air produces more liquid water than cold saturated air
TRUE
the moist adiabatic rate is equal to?
an average of 6°C per 1000 m.
if the air in a stable atmosphere strongly resists
upward vertical motion, and is forced to rise,
it tends to
spread out horizontally
Expected clouds to see in a stable atmosphere
cirrostratus, altostratus, nimbostratus, or
stratus
The cooling of the surface air may be due to:
- nighttime radiational cooling of the surface
- an influx of cold surface air brought in by the wind
- air moving over a cold surface
If the surface air becomes saturated in a stable
atmosphere, a __________ may
form
a persistent layer of haze or fog
The atmosphere is unstable when the
air temperature __________ as we
move up into the atmosphere.
decreases rapidly
The warming of the surface air may be due to:
- daytime solar heating of the surface
- influx of warm surface air brought in by the wind
- air moving over a warm surface
Instability brought on by the lifting of air is often associated with
the development of
severe weather, such as thunderstorms and
tornadoes
The following mechanisms are responsible for the development of the majority of clouds we observe:
- surface heating and free convection
- uplift along topography
- widespread ascent due to the flowing together
(convergence) of surface air - uplift along weather fronts
Forced lifting along a topographic barrier is called
orographic uplift
The most important factor in the production of raindrops is
the
cloud’s liquid water content
In a cloud with sufficient water, other significant factors are:
- The range of droplet sizes
- the cloud thickness
- the updrafts of the cloud
- the electric charge of the droplets and the electric field in
the cloud
Water droplets existing at temperatures below
freezing are referred to as
supercooled droplets
Examples of excellent ice nuclei’s
clay minerals, bacteria in decaying plant leaf
material, and ice crystals
The primary goal in cloud seeding is to
inject (or seed) a cloud with small particles that will act as nuclei
The most common chemicals used for cloud seeding
include
salt, silver iodide, potassium iodide and dry ice
(solid carbon dioxide).
Aims at speeding up droplet coalescence in
liquid clouds, leading to production of large
droplets that start to precipitate.
HYGROSCOPIC CLOUD SEEDING
Cloud seeding material consists usually of large salt particles
dispersed by some means to the cloud base.
HYGROSCOPIC CLOUD SEEDING
Aims to trigger ice production in supercooled clouds,
leading to precipitation.
GLACIOGENIC CLOUD SEEDING
For it to be considered as rain, the water droplet must have a diameter equal to, or greater than
RAIN
Fine uniform drops of water whose diameters are
smaller than 0.5 mm is called
Drizzle
Evaporating streaks of precipitation are called
VIRGA
Drizzle is mostly from
stratus clouds
If the updraft weakens or changes direction and becomes a
downdraft , the suspended drops will fall to the ground as a
sudden rain
shower
The showers falling from cumuliform clouds are usually brief
and sporadic, as the cloud moves overhead and then drifts
on by. If the shower is excessively heavy, it is termed a
cloudburst
When ice crystals and snowflakes fall from high cirrus clouds
they are called
fallstreaks
Snow falling from developing cumulus clouds is often in the form
of
flurries
These are usually light showers that fall intermittently
for short durations and produce only light accumulations.
flurries
A more intense snow shower is called a
snow squall
A weather condition characterized by low
temperatures and strong winds (greater than 30 knots)
bearing large amounts of fine, dry, powdery particles of
snow, which can reduce visibility to only a few meters
Blizzard
partially melted snowflake or cold raindrop turns back into ice, not as a snowflake, but as a tiny transparent (or translucent) ice pellet
Sleet
The cold surface layer beneath a cloud may be too shallow to freeze raindrops as they fall. In this case, they reach the surface as supercooled liquid drops. This is called
FREEZING RAIN OR GLAZE
snow grains came from ____ clouds
stratus
snow pellets came from _____ clouds
Cumulus congestus
Pieces of ice either transparent or partially opaque, ranging in size from that of small peas to that of golf balls or larger Some are round, and others take on irregular shapes.
Hail
Hail is produced in a ______ cloud
cumulonimbus
For a hailstone to grow to golf ball-size, it must
remain in the cloud between
5 to 10 minutes
