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Meteorology Clouds. Reference. From the Ground Up Chapter 6.2: Clouds Pages 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.
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Reference From the Ground Up Chapter 6.2: Clouds Pages 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 – Meteorology Pressure From the Ground Up Chapter 6.3: Pressure Pages 127 - 130