1) collision-coalescence - warmer clouds, liquid water...

Cloud Droplet Growth Processes: 1) Collision-Coalescence

- warmer clouds, liquid water only - different size drops fall at different speeds

2) Ice-Crystal Process

- colder clouds with both liquid water and ice

Clicker Question

The collision-coalescence process is most efficient when: (A) all the cloud droplets are small (B) all the cloud droplets are large (C) there is a mix of small and large cloud droplets

Set Frequency to "BB"

Collision - Coalescence Process (Warm process)

Cloud Droplet Growth Processes: 1) Collision-Coalescence

- warmer clouds, liquid water only - different size drops fall at different speeds

2) Ice-Crystal Process

- colder clouds with both liquid water and ice

T=0°C (Freezing level)

Liquid Only

Surface

Tall Cumulonimbus Cloud

T=0°C (Freezing level)

T=-40°C

Liquid Only

Supercooled Liquid and Ice

Ice Only

Surface

Tall Cumulonimbus Cloud

This region is where Ice-Crystal Process occurs

Question: How can liquid water exist below freezing point? - need freezing nuclei for liquid water to freeze into ice crystal if temperature is between 0 and -40°C. - similar idea as cloud condensation nuclei, except the structure of freezing nuclei must be similar to structure of ice crystal ==> As a result, much fewer freezing nuclei in atmosphere compared to number of cloud condensation nuclei

In Equilibrium: Condensation = Evaporation

Liquid Drop and Water Vapor

Ice Crystal and Water Vapor

water vapor liquid water ice crystal

In Equilibrium: Condensation = Evaporation

Liquid Drop and Water Vapor

Ice Crystal and Water Vapor

More Water Vapor Around Liquid Drop

Less Water Vapor Around Ice Crystal

water vapor liquid water ice crystal

Now, put Liquid Drop and Ice Crystal Together

Liquid Drop and Water Vapor

Ice Crystal and Water Vapor

More Water Vapor Around Liquid Drop

Less Water Vapor Around Ice Crystal

water vapor liquid water ice crystal

Now, put Liquid Drop and Ice Crystal Together

water vapor liquid water ice crystal

Now, put Liquid Drop and Ice Crystal Together

Now more water vapor around Ice Crystal => Vapor condenses on Ice

water vapor liquid water ice crystal

Now, put Liquid Drop and Ice Crystal Together

Now more water vapor around Ice Crystal => Vapor condenses on Ice

water vapor liquid water ice crystal

Now, put Liquid Drop and Ice Crystal Together

Now more water vapor around Ice Crystal => Vapor condenses on Ice As water vapor decreases => Liquid water evaporates from drops

water vapor liquid water ice crystal

Now, put Liquid Drop and Ice Crystal Together

water vapor liquid water ice crystal

Now more water vapor around Ice Crystal => Vapor condenses on Ice As water vapor decreases => Liquid water evaporates from drops

=> Ice Crystal Grows => Liquid Drop Shrinks

Ice Crystal Process (also referred to as Bergeron Process)

Sleet - rain refreezes before hitting surface - deeper cold layer near surface

Sleet

Freezing Rain - rain refreezes on contact with surface - shallow cold layer near surface

Sleet - rain refreezes before hitting surface - deeper cold layer near surface

Freezing Rain

Freezing Rain

Freezing Salt Water Spray?

Rime: Fog droplets freeze on contact

Clicker Question

Red line = Temperature Green line = Dew Point Temperature

Set Frequency to "BB"

Clicker Question

Red line = Temperature Green line = Dew Point Temperature At what altitude would you expect clouds? (A) 2-4 km (B) 4-6 km (C) 6-8 km (D) 8-10 km

Set Frequency to "BB"

Clicker Question

Red line = Temperature Green line = Dew Point Temperature At what altitude would you expect clouds? (A) 2-4 km (B) 4-6 km (C) 6-8 km (D) 8-10 km

Set Frequency to "BB"

cloud

Clicker Question

Red line = Temperature Green line = Dew Point Temperature What would the cloud consist of? (A) liquid drops only (B) ice crystals only (C) both liquid drops and ice crystals

Set Frequency to "BB"

cloud

Clicker Question

Red line = Temperature Green line = Dew Point Temperature What would the cloud consist of? (A) liquid drops only (B) ice crystals only (C) both liquid drops and ice crystals

Set Frequency to "BB"

cloud

Clicker Question

Red line = Temperature Green line = Dew Point Temperature Precipitation reaching the surface would be: (A) rain (liquid only) (B) freezing rain (C) sleet (D) snow

Set Frequency to "BB"

cloud

Clicker Question

Red line = Temperature Green line = Dew Point Temperature Precipitation reaching the surface would be: (A) rain (liquid only) (B) freezing rain (C) sleet (D) snow

Set Frequency to "BB"

cloud