Cloud Classification Flashcards
What can clouds indicate to pilots?
Turbulence, Icing, Poor visibility, windshear, wind direction, wind direction, Tropopause level
Why do clouds form?
When air becomes cooled to dew point
and/or
Evaporation causing air to saturate (above a water source etc)
Give the definition of Adiabatically
Adiabatically is a process that occurs without the exchange of heat energy.
How does air cool Adiabatically?
Air cools Adiabatically, due to expansion - as it rises through lower pressure within the upper troposphere.
(the lower pressure allows the air molecules to spread out)
What is the Dry Air Lapse Rate (DALR)?
DALR = 3°C / 1000ft
What is the Saturated Air Lapse Rate (SALR)?
SALR = 0.5°C / 1000ft
What is the Saturated Air Cooling Rate (SALR)?
SALR = 1.8°C / 1000ft
Give examples of condensation nuclei
Dust, smoke, bacteria, algae, sand, salt crystals, clay, soot, plankton, sulphates from volcanoes
What are the sizes of the average: rain drop, cloud droplet, condensation nuclei?
Rain drop = 2 mm
Cloud droplet = 0.02 mm
Condensation nuclei = 0.0002 mm
What is the equation to calculate cloud base?
Cloud base = 400 (Ta - Td)
What are the 5 ways that air is lifted?
Convection Turbulence Frontal lift Orographic lift Convergence
Give a basic description of a Stratus cloud
Generally flat + low
Wide, but not tall
Give a basic description of a Cumulus cloud
Tall + low
But not very wide
Have a ‘cauliflower’ appearance
Give a basic description of a Cirrus cloud
Fibrous + wispy
With a high altitude
Give the definition of a cloud base
The height above ground, of the lowest cloud (ft)
Give the definition of Cloud ceiling
Height above ground, of the lowest cloud layer - covering over half of the sky (4 oktas)
Give the definition of Cloud top
The altitude of the top of the clouds, in FL or Ft
Low level clouds in Ft
List the cloud coverage scales - including abbreviations and numerical value
0 = Sky clear (SKC) 1-2 = Few (FEW) 3-4 = Scattered (SCT) 5-7 = Broken (BKN) 8 = Overcast (OVC) 9 = Sky obscured (cannot see - fog/smoke)
How does convection form clouds?
Air rising cools at DALR, until Ta = Td —- forming clouds (base)
Then still, cooling at SALR, until Ta = Td again —- no clouds (top)
How does turbulence form clouds?
Air flowing over a rough surface, or thermal lifting - can result in a turbulent layer of air at around 3000ft (friction layer)
Air mixing with this layer results in an inversion forming. Near the top of this layer, the air is cooled to dew point - and clouds form.
Generally forming Stratocumulus (with light turbulence within)
What are the high categories of clouds?
Low level —— No prefix —— Surface - 6500ft
Medium level —— Alto —— 6500 - 23000ft
High level —— Cirro —— 16000 - 45000ft
How does the climate region affect cloud levels?
Within a tropical climate:
High level — Base and top rise
Medium level — Top rises
Low level — No effect
What are the 10 different cloud genera?
Give with increasing height
All level = Cumulonimbus, Nimbostratus
Low level = Stratus, Cumulus, Stratocumulus
Mid level = Altostratus, Altocumulus
High level = Cirrostratus, Cirrocumulus, Cirrus
Give the abbrev. for all level clouds
Cumulonimbus = CB
Nimbostratus = NS
Give the abbrev. for low level clouds
Stratus = ST
Cumulus = CU
Stratocumulus = SC
Give the abbrev. for mid level clouds
Altostratus = AS
Altocumulus = AC
Give the abbrev. for high level clouds
Cirrostratus = CS
Cirrocumulus = CC
Cirrus = CI
What are the 5 species of cloud?
Castellanus — Turreted (like castle towers)
Lenticularis — Lentil-like (wide, round top, flat bottoms)
Fractus — Broken
Humilis — Small, fair weather
Congentus — Heaped, towering
Name the supplementary features
Anvil —- hammer top (Capillatus - when ‘hairs’ from this) Mammatus —- udders Virga —- rain not reaching the ground Roll —- cylinder-like Tornado —- waterspout if in water Towering
What are the 2 methods of measuring cloud base?
Ceilometer —- laser, or light source used to measure cloud height
(Can also use satellite observations - through infrared or triangulation)
What is the abbrev. for a Significant weather chart?
SIGWX
What are the 5 categories used to measure amount of cloud on a SIGWX?
ISOL - isolated OCNL - occasional FRQ - frequent EMBD - embedded WDSPD - widespread
