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Pg. 71. Moisture in the atmosphere. Cloud formation. The tendency to rise or sink because of differences in density is called buoyancy Clouds form when warm, moist air rises, expands, and cools around condensation nuclei. Condensation nuclei mainly form from dust and salt
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Pg. 71 Moisture in the atmosphere
Cloud formation • The tendency to rise or sink because of differences in density is called buoyancy • Clouds form when warm, moist air rises, expands, and cools around condensation nuclei. • Condensation nuclei mainly form from dust and salt • When air is pushed up a mountain orographic lifting occurs • Also form when air masses of different temperatures collide
Stability • How rapidly a given mass cools determines stability • Depends on the temp below the surface • Air becomes unstable if it is cooler than the surface beneath it • The warm air rises and becomes less dense than the air around it and can create thunderstorms
Latent Heat • Heat is released as water vapor condenses • Takes energy to change liquid to gas so energy gets stored until condensation occurs • Latent heat warms the air when condensation is released • Latent heat can provide energy to a weather system increasing the intensity
Types of clouds • When air reaches its LCL, droplets form in either liquid or ice form • If the density is great enough, they form clouds • Classified by altitude and shape
Cloud Classification • Height • Cirro- high clouds with bases above 6000m • Alto- middle clouds between 2000m and 6000m • Strato- clouds below 2000 m • Shape • Cirrus- means ‘hair’ describes wispy clouds • Cumulus- means ‘pile’ describes puffy clouds • Stratus- means ‘layer’ describes sheets of clouds • Nimbus- means ‘cloud’ describes low, grey clouds
Low Clouds • Stratocumulus clouds- flattened cloud • Stratus cloud- covers much or all of the sky in a given area • Forms when fog lifts
Middle Clouds • Altocumulus and altostratus clouds can be all liquid or mixture of liquid and ice • Usually layered
High clouds • Made of ice crystals • Cirrus clouds- wispy appearance • Cirrostratus- continuous layer; vary in thickness
Clouds of vertical development • Clouds that are colder than the surrounding air can continue to grow producing a cumulonimbus cloud
Precipitation • Coalescence takes place • Drops become too heavy and precipitation occurs • Convective currents can move droplets up and down forming hail
The water cycle • Receives energy from the Sun • Causes liquid to change to gas (evaporate) • Evaporation is the first step in the water cycle • Water cools and changes back to a liquid (condensation) and forms clouds • Then precipitation occurs • Evaporation begins again
Pg. 72 • You are going to construct a diagram like the one below. In you diagram you need to include the following: • Evaporation and condensation processes • A source of ground water and surface water • The source of energy that drives the water cycle • 2 different types of clouds • Where an LCL would be • 2 different ways clouds can form • precipitation