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Flashcards in lol short term memory let's go Deck (18):
1

What is the recipe for precipitation?

Unsaturated air rises and cools by adiabatic expansion, reaching saturation.
Presence of cloud condensation nuclei (CCN, such as aerosol) allow for condensation, leading to formation of tiny droplets.
Droplets grow by additional condensation

2

For rain to occur, what must happen

Velocity > water

3

Warm Clouds: Collision-Coalescence

Growth in warm clouds (T>0°C) – mostly in the tropics and warm season in midlatitudes
• Two droplets collide and coalesce (i.e., merge)
• Promoted by large collector drops, which have high
terminal velocities
• More efficient in clouds with large distribution of droplet sizes and strong updrafts

4

At top of cold/cool clouds:

it's glaciated- there's ice and vapor -> not much growth!

5

What happens at T<0 Cels

Mixed ice and supercooled water droplets (all three phases co-exist)
1. Bergeron process
2. Riming
3. Aggregation

6

What happens at T>0 Cels

liquid droplets and vapor (Same as warm cloud: collision-coalescence)

7

What is the bergeron process?

• Saturation vapor pressure of ice is less than that of supercooled water
• Water vapor is satured over supercooled water, but supersatured over ice
• Ice crystals grow rapidly at the expense of supercooled droplets (via net deposition and net evaportaion)

8

What is riming?

(liquid water freezes onto ice crystals)

9

Aggregation

(ice crystals collide and merge via thin coating of liquid water)

10

What limits the growth of ice particles by the Bergeron process?

The amount of supercooled water in the cloud & The time an ice particle remains in the cloud

11

Describe snow crystals

Snow crystals: single crystals
• Shapes of ice crystals (crystal habits) depend on temperature and degree of supersaturation (for ice)

12

Snowflakes

Snowflakes: aggregates of snow crystals
Warmer clouds: snowflakes formed by riming which forms dense “wet” snowpack (snowball fights)
Colder clouds: snowflakes formed by aggregation which forms less dense powdery snowpack (skiing)

13

Lake Effect Snow:

develops as the warm lake waters evaporate into cold air

14

Warm clouds:

predominant in tropics

15

Cold Clouds:

Most middle-latitude precipitin starts out as snow, then melts to rain.

16

Graupel

Rimed ice crystal

17

Hail

concentric layers of ice built around graupel- wet growth results in solid ice

18

possible types of precipitation originating from a cold cloud:

Rain, Snow, Hail, Graupel, Freezing rain, Sleet