What are the two ways water droplets form? Which never happens in nature?

Heterogenous and homogenous nucleation. Heterogenous nucleation only happens in labs.

Hydrophilic aerosols are called what?

cloud condensation nuclei (CCN)

______________ nuclei dissolve in water.

Hygroscopic

Is it easier or harder for water to evaporate from a solution?

Harder

A droplet’s size is directly related to the relative
humidity at which it will be in equilibrium (continue to exist). What is this effect called and what does it mean in practice?

The curvature effect. The larger a droplet the harder it will be for it to evaporate.

What are the three ways ice crystals form (with the help of ice nuclei).

• Directly from vapour if water vapour is deposited onto
ice nuclei
• When a supercooled water droplet already contains an
ice nucleus and temperatures get cold enough
• When supercooled droplets (with a non ice nuclei) collide with ice nuclei

What condition does the presence of solutes change for forming water droplets? What is this effect called?

The relative humidity at which water droplets form which can be lower than 100%. The solute effect.

In order for a droplet to increase in radius/diameter what must also increase to maintain the droplet/s existence?

The relative humidity

What are the three favoured traits of an aerosol for condensation?

wettable (hydrophilic), large (so it's harder for the droplet to evaporate), and hygroscopic (dissolves in water)

What condition does the presence of solutes change for forming water droplets? What is this effect called?

The relative humidity at which water droplets form which can be lower than 100%. The solute effect.

Why is dust not a good CNN?

It doesn't dissolve

When the water droplets in clouds start to precipitate their relative humidity's...?

Drop/decrease

Why does the size of droplets tends to become uniform in a cloud?

Small droplets grow faster than big ones so all droplets get to be big and then kinda stop growing.

Larger droplets freeze at slightly higher temperatures than their smaller counterparts, true or false?

True

What temperature must it be in a cloud (in nature) for water droplets to freeze?

negative 40 degrees Celsius

When the water droplets in clouds start to precipitate the cloud's relative humidity...?

Drops/decreases

Favourable ice nuclei are _________ and ______________.

Name two examples of ice nuclei.

large and insoluble,

• Clay minerals
• Combustion products
• Organic material

What are the three ways ice crystals form (with the help of ice nuclei).

• Directly from vapour if water vapour is deposited onto
ice nuclei
• When a supercooled water droplet already contains an
ice nucleus and temperatures get cold enough
• When supercooled droplets (with a non ice nuclei) collide with ice nuclei

What are the three ways to achieve saturation?

• Cooling the air to its dew-point temperature
• Adding water vapour to the air
• Mixing air samples

Clouds form due to...?

rising air

What are the five basic mechanisms by which air rises to form clouds?

• Convection
• Orographic lifting
• Convergence of surface winds
• Frontal lifting
• Divergence aloft

Which lifting mechanism is this?

Orographic lifting

Which lifting mechanism is this?

Convergence

Which lifting mechanism is this?

Convection

Which lifting mechanism is this?

Frontal lifting

Name the lifting mechanism in b, c and d

The classification of clouds is based on __________ and ___________.

shape and height

Howard’s identification system uses Latin
roots. What are these words mean in English?

• Cumulus
• Stratus
• Cirrus
• Nimbus

• Cumulus (“heap”)
• Stratus (“layer”)
• Cirrus (“curl of hair”)
• Nimbus (“rain”)

________ ____________ cause cirrus clouds to have ragged edges.

Ice crystals

Of the classifications cirrus, cumulus and stratus which clouds are found only at high altitudes?

Cirrus

Cumuliform Clouds (e.g., cumulus, stratocumulus,
cumulonimbus) form in ______________ air.

unstable

Cumulus humilis clouds are (small/large) and only last for a few minutes or hours.

small

Fill in the blanks:

Cumulus humilis -> time -> Cumulus _______________ -> rise until reaches a __________ ___________ -> ___________________ -> heavy precipitation

Cumulus humilis -> time -> Cumulus congestus -> rise until reaches a stable layer -> precipitation -> cumulonimbus -> heavy precipitation

Stratiform Clouds (e.g., stratus, stratocumulus,
nimbostratus) form in ____________ air as a result of forced lifting or as winds cause turbulent mixing.

stable

_______________ fog forms as air rising up a slope cools adiabatically. Other fogs form by mixing or
adding ____________ _____________.

Upslope, water vapour

Radiation Fog forms when _____________ of radiation by the ___________ are mixed with water droplets through the mixed layer via ___________ __________.

emissions, surface, light wind

Advection Fog forms due to conductive cooling as _________, ___________ air is advected over a cool surface

warm, moist

What are the three ways to achieve saturation?

• Cooling the air to its dew-point temperature
• Adding water vapour to the air
• Mixing air samples

Name the four main fog types.