Download - Meteorology Clouds
Sep 2012
Lesson 4.2
Meteorology
Clouds
Reference
From the Ground UpChapter 6.2:CloudsPages 124 - 127
Introduction• Clouds can form in different ways and,
as a result, come in many different types.
• Pilots should know the properties of different types of clouds, and what weather conditions come with them.
Outline• Classifications• Sky Condition• Cloud Formation
Classifications• By formation:
– Cumulus – Vertical clouds, formed by rising air, indicates Unstable Air
– Stratus – Horizontal layers, indicates Stable Air
• By height (families):– Low (Strato) Surface – 6 500 ft– Middle (Alto) 6 500 ft – 23 000 ft– High (Cirro) 16 500 ft – 45 000 ft– Vertical Development 1 500 ft and up
High Clouds• Cirrus (Ci)
– Thin wavy, delicate wisps
High Clouds• Cirrocumulus (Cc)
– Thin cotton ball or flake-like
High Clouds• Cirrostratus (Cs)
– Very thin, high sheets– Makes sky white, halo around sun or moon
Middle Clouds• Altocumulus (Ac)
– Layer or patches of rounded masses
Middle Clouds• Altocumulus Castellanus (Acc)
– Altocumulus with turrets
Middle Clouds• Altostratus (As)
– Thick grey layer– Sometimes light rain/snow
Low Clouds• Stratus (St)
– Uniform layer like fog, but not on ground,Sometimes has drizzle
– When broken, called Stratus Fractus (Sf)
Low Clouds• Statocumulus (Sc)
– Thin layer or patches of rounded masses
Low Clouds• Nimbostratos (Ns)
– Uniform thick, dark, grey layer– Continuous rain/snow
Vertical Development• Cumulus (Cu)
– Thick, rounded or lumpy individual clouds– When fragmented, called Cumulus Fractus (Cf)
Vertical Development• Towering Cumulus (TCu)
– Very high towering masses– Rough air underneath
Vertical Development• Cumulonimbus (Cb)
– High, heavy masses going above freezing level– Usually hail inside cloud, heavy rain/snow beneath– Very turbulent
Sky Condition• Cloud cover broken down into oktas (8ths):
– Clear 0– Few 1 - 2– Scattered 3 - 4– Broken 5 - 7– Overcast 8
• Broken and Overcast considered a Ceiling
Cloud Formation• Clouds form from condensation or sublimation
(water vapour to water droplets or ice). This requires:– High relative humidity– Condensation nuclei– Cooling air
• Formed in two ways:– Air cools to saturation point (most common, by
expansion)– Air absorbs water vapour to reach saturation point
Lifting Processes• Clouds created when air rises, expands,
cools, condenses. Following processes force air up:– Orographic Lift – Air forced up by hills/mountains– Convection – Sun heats ground, warm air rises– Frontal Lift – Warm air forced up over cold front– Turbulence – Wind blowing over rough ground
creates eddies, forcing up and down currents– Convergence – Air inside a low pressure area is
forced upwards
Next Lesson
4.3 – MeteorologyPressure
From the Ground UpChapter 6.3:PressurePages 127 - 130