Precipitation Flashcards
How does Collision/Coalescence form rain drops?
Especially in clouds with a lot of movement - water droplets collide and merge together.
This causes an increase in size of (cube root 2)
Cumuliform clouds form big droplets quicker
How does the Bergeron process form rain drops?
Within a cloud with both supercooled waters droplets and ice crystals (Cloud top <0°C, Cloud base >0°C)
Water vapour is lifted in up-draughts.
When they reach the higher level within the cloud, they have low energy.
Ice crystals have a lower vapour pressure than water droplets - therefore the water vapour sublimates to ice; forming larger ice crystals.
As these ice crystals fall, they either melt, or form ice pellets.
What are the symbols for the types of Precipitation?
‘ = Drizzle (0.2-0.5mm) • = Rain (0.5-5.5mm) * = Snow (1-5mm - 3 types) ▲ = Hail (5-50mm) Δ = Snow hail (Graupel) (<5mm)
Freezing rain = (laying S with • within) (<5mm)
Freezing drizzle = (laying S with ‘ within) (<5mm)
Which cloud type do showers fall from?
Cumuliform clouds
What types of precipitation come from low level clouds?
ST - Drizzle (DZ), Snow grains (SG), Ice crystals (IC)
CU - Rain (RA)/Snow (SN) showers
SC - Rain, Snow, Soft hail/Snow pellets
What types of precipitation come from mid level clouds?
AS - Rain (RA), Snow (SN), Ice Pellets (PL)
AC - Rain/Snow Showers
What is the abbrev. for Freezing rain?
Freezing rain = FZRA
What are the 3 categories of continuity, and which clouds produce them?
Continuous - 60 mins, no breaks
AS or NS
Intermittent - Continuous, with breaks
AS or SC
Showers - Cumuliform cloud
CU or CB
What types of precipitation come from all level clouds?
CB - Snow pellets/Soft hail, Small Hail (GS), Hail (GR), Rain/Snow showers
NS - Rain (RA), Snow (SN), Ice pellets (PL)
What is the visibility in moderate and heavy rain?
Moderate = 3-10 km
Heavy = < 1000 m
What is the visibility in moderate, heavy and blowing snow?
Moderate = 1000 km
Heavy = < 50 m
Blowing = Few m
What is the visibility in drizzle?
Drizzle = < 50 m
