Transcript Guided Notes on Moisture in the Atmosphere

Guided Notes on Moisture
in the Atmosphere
Chapter 11, Section 3
1. Clouds form when warm, moist
air rises, expands, and cools in a
convection current.
2. When air reaches the dew point, water
vapor condenses around condensation
nuclei, which are small particles in the
atmosphere around which cloud droplets
form. Examples of condensation nuclei
are sea salt and dust. When millions of
droplets collect, a cloud forms.
3. Clouds also form through
orographic lifting, which is when
wind encounters a mountain and
the air has no place to go but up.
4. Sometimes clouds form when two air
masses of differing temperatures collide.
As warm air moves into an area of cool
air, the bulk of it will be forced to rise
over the more-dense, cold air. As warm
air rises and cools, the water vapor in it
condenses and forms a cloud.
5. Air can become unstable if it is
cooler than the surface beneath it. If
temperature conditions are right and
the air mass rises rapidly, it can
produce the types of clouds
associated with thunderstorms.
6. As water vapor in the air condenses,
heat is released. This heat warms
the air. This latent heat can provide
energy to a weather system, thereby
increasing its intensity.
7. When cloud droplets collide, they
join together to form a larger droplet
in a process called coalescence.
Eventually the droplet becomes too
heavy to be held aloft and the
droplet falls to Earth as precipitation.
8. Examples of precipitation
include rain, snow, sleet, and
hail.