Cloud Microphysics

Question 1

Supersaturation

Answer 1

the air contains more water vapour than is needed to cause saturation

Question 2

Nucleation

Answer 2

describes initial formation of droplet or ice

Question 3

Homogenous Nucleation

Answer 3

• droplets spontaneously form in pure air
• no particles present in the droplet formation

Question 4

Heterogenous nucleation

Answer 4

• droplets form on particles (aerosols) called cloud condensation nuclei

Question 5

Curvature (kelvin) effect

Answer 5

• greater probability that molecules from curved surface can escape from surface of liquid
• saturation over curved surface needs to be higher than over flat surfaces to keep drop in equilibrium

Question 6

Solute

Answer 6

chemical that is being dissolved

Question 7

Solvent

Answer 7

chemical that dissolves solute

Question 8

Processes of precipitation drop growth

Answer 8

1. Warm cloud processes (only liquid drops)
2. cold cloud processes (ice and liquid drops)

Question 9

Types of droplet collisions

Answer 9

collision-coalescence: large drops collect small drops
riming: falling ice collects liquid water and freezes
capture nucleation: Large drops capture small ice particles which results in the freezing of the drop
aggregation: falling snowflakes collect smaller snowflakes

Question 10

Supercooled water

Answer 10

-liquid water with temp<0C
- homogenous nucleation: if water is pure then spontaneous freezing will occur at -40C
- heterogenous nucleation: water impurities cause freezing around ice nucleus to occur much higher than -40C

Question 11

Bergeron Process