Precipitation Flashcards
How is freezing rain encountered
Supercooled water freeze on contact under warm front
Typically ahead of warm front from Nimbostratus cloud
Drizzle Facts
Referred to as DZ
Falls from Stratus Cloud
Less than 0.5mm
No splash
Rain Facts
0.5 to 5.5mm
Falls from stratiform or cumuliform clouds
Snow Facts
Falls in temps between +2 and -5 degrees
Largest flakes being close to 0 degrees
Falls from stratiform or cumuliform
Hail Facts
Small Hail (GS) less than 5mm
Hail (GR) bigger than 5mm
Freezing/melting in CB clouds
Water droplets speed/dimension
0.02mm
0.012m/s
Snow Pellets
Conical 2-5mm
Break on contact
Cumulus Cloud
Ice Pellets (PL)
Clear ice
Bounce on impact
Fall from NS or thick AS
Indication of freezing rain above
Ice Crystals
Referred to as diamond dust
Can fall from clear skies
Temp so low water freezes in air -35 degrees
Bergeron Theory
Supercooled water droplets and ice crystals mixing in cloud to get bigger.
Saturation vapour over water is greater than ice therefore water vapour collided with SCWD becoming heavier and then drop out of the cloud as snow or rain
Coalescence Process
Occurs in warm lower clouds
Above -15 degrees
Collision of falling and rising droplets allowing them to grow large enough to fall as precipitation
Produces only drizzle or very light rain
Drizzle
Less than 0.5mm
Stratus
Does not make a splash
Rain
0.5 or 5.5mm
Falls from stratiform of cumuliform cloud
What is directly measured by a radiosonde
Atmospheric pressure
Air temperature
Humidity
SQ
Squalls - strong winds of at least one minute minimum 16kt increase in wind
