Cloud Development

Atmospheric Basics

Atmospheric Composition

Atmospheric Basics

Atmospheric Composition
Key Atmospheric Gases

– The amount of water vapor in the
atmosphere can be as much as four
percent of the atmosphere or as little as
almost zero.
– Carbon dioxide, another variable gas,
makes up under one percent of the
atmosphere.

State of the Atmosphere

Temperature Versus Heat
 Temperature is a measurement of how
rapidly or slowly molecules move.

 Heat the transfer of thermal energy from
one substance to another.

 Heat is the transfer of energy that fuels
atmospheric processes, while temperature
is used to measure and interpret that
energy.


Measuring Temperature
– Temperature can be
measured in degrees
Fahrenheit (°F), in
degrees Celsius (°C),
or in kelvins (K), the
SI unit of temperature.

– The Kelvin scale
measures the number of
kelvins above absolute
zero, a point where
molecular motion
theoretically stops.


Dew Point
– The dew point is the temperature to which air must be
cooled in order for it to be saturated to trigger
condensation.

a) Saturation is the point at which the air holds as much
water vapor as it possibly can.
b) Condensation cannot occur until air is saturated.

– Condensation occurs when matter changes state
from a gas to a liquid.

Moisture in the Atmosphere

Cloud Formation
 Buoyancy is the tendency for air to rise or sink
as a result of differences in density.
 There are 3 ways that clouds can form:
1) Clouds form when warm, moist air rises,
expands, and cools in a convection current.

 Condensation nuclei
are small particles in the
atmosphere around
which cloud droplets
can form.


Cloud Formation
2) Orographic lifting occurs when wind
encounters a mountain and the air has no
place to go but up.
 The air expands and cools resulting in
cloud formation.


Cloud Formation
3) Cloud formation occurs with the collision of
air masses of different temperatures.
 As warmer air collides with cooler air, the
bulk of it will be forced to rise over the
more-dense, cold air.
 As the warm air
cools, the water
vapor in it
condenses and
forms a cloud.


Cloud Formation
Stability
– How rapidly any given mass of air cools determines
its stability.
– Stability is the ability of an air mass to resist rising.

– The rate at which an air mass cools depends in part
on the temperature of the surface beneath the air.
– Air can become unstable if it is cooler than the surface
beneath it.
– If temperature conditions are right and the air mass
rises rapidly, it can produce the type of clouds
associated with thunderstorms.


Cloud Formation
Latent Heat
– As water vapor in the air condenses, heat is
released.
– The energy to change liquid water into a
gaseous state is stored in the water vapor.
– Latent heat is stored energy in water vapor
that is not released to warm the atmosphere
until condensation takes place. “Hidden –
Heat”
– The amount of water vapor present in the
atmosphere is a significant source of energy
because of the latent heat it contains.


Types of Clouds
 The modern
system groups
clouds by the
altitude at which
they form and by
their shape.

– Low clouds typically
form below 2000 m.

– Middle clouds form between 2000 m to 6000 m.

– High clouds composed of ice crystals form
above 6000 m.

The halo around the sun or moon is a layer of cirrus
clouds made of ice crystals. These ice crystals act as
tiny prisms, forming a white or sometimes colorful halo
around the sun or moon. This cirro-stratus cloud often
indicates an approaching warm front and an
associated area of low pressure. Rain or snow will not
always follow, but there is a higher probability of it
after a halo is seen, and the brighter the circle, the
greater the probability.

– Vertical development clouds spread throughout
all altitudes at the same time.


Types of Clouds

Wispy, feather-like,
High clouds ice crystals.

Puffy, cotton-like,
Fair weather clouds
Middle clouds

Sheets, layers

Low clouds
Storm clouds

Types of Clouds

Types of Clouds 3:17 minutes


Precipitation
 Coalescence occurs when cloud droplets
collide and join together to form a larger
droplet.
 When the droplet becomes too heavy to be
held aloft, gravity takes over and it falls to
Earth
as precipitation.
 Precipitation includes all forms of water,
both liquid and solid, that fall from clouds
including
rain, snow, sleet, and hail.

Precipitation
 When water vapor in the clouds becomes
too heavy, it can fall as rain, sleet, snow,
or hail.
 Cloud droplets must first increase in size
until gravity pulls them down.
 If they pass through extremely cold layers
of air, they can freeze and produce sleet
 Snow is formed when water vapor
changes directly into a solid.
 Hail is formed when water droplets freeze
in layers due to updrafts and downdrafts.


The Water Cycle
 At any one time, only a small percentage of
water is present in the atmosphere.

 The water cycle is the constant movement
of water between the atmosphere and
Earth’s surface.

Exit Ticket (Write Question
Out
1. Name the 5 atmospheric layers.
2. Describe what the magnetosphere is.
3. What are the 3 ways that energy in the
atmosphere can be transferred on
Earth?
4. How are clouds classified?
5. What are the prefixes to describe
height: a) low b) middle c) high clouds?
6. What are the prefixes to describe the
shapes of clouds: a) wispy b) puffy c)
layered d) storm

Cloud Development

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