How does dew form?
Clear calm night
Objects close to the ground cool rapidly by emitting infared radiation
ground and objects become colder than surrounding air
air in contact with these surfaces cools by conduction
given enough time, air will cool to the Dew point
water then condenses to the cold surfaces
dew will freeze if temperature drops below freezing
How does frost form?
Formation similar to dew or frozen dew
Dew point starts out below freezing (frost point)
water vapor changes directly to ice without becoming a liquid
Condensation Nuclei versus cloud condensation nuclei?
Cloud condensation nuclei greater than 1 micrometer, cloud condensation nucli are actual clouds.
What are the particles that make up cloud condensation nuclei?
Dust, volcanoes, smoke, salt, sulfate particles emitted by phytoplankton.
What does Hygroscopic mean?
Below what RH does condensation not form?
Below 80 Percent.
How does fog form, give 2 ways.
- forms best on clear night when a shallow layer of moist air is below a larger layer of dry air.
- the shallow layer does not absorb much of the outgoing IR radiation from the surface.
- the ground, therefore, cools very rapidly
- the air above the layer also cools very rapidly and a surface inversion forms.
- the moist layer is chilled by the cold surface and becomes saturated.
- surface air is cooled my moving warm moist air over a cold surface
- example: Pacific coast during summer
- - surface water near the coast is much colder than surface water offshore
- - warm, moist air from the Pacific Ocean is carried by westerly winds over the cold, coastal waters
- also forms over land
- - warm, moist air from the Gulf of Mexico moves Northward over colder, elevated land
- - this fog is called advection-radiation fog
Why is fog more dense over cities?
Evaporation or Mixing Fog
Forms when warm unsaturated air moves into cooler unsaturated air, moistening it to evaporation. Common when cool air moves over a non frozen lake.
Where do you find Lenticular Clouds?
Crest of wave
Banner or cap cloud
lenticular cloud that forms downwind of a mountain peak.
Cloud that hangs like sacks, formed by sinking air with high moisture content.
Exhaust particles, hygroscopic and attracts water
An unusual cloud best viewed at winter in the poles and forms in the stratosphere.
An unusual wavy cloud that is best viewed at the poles and forms in the upper mesosphere.
Why are clouds white?
clouds are white because their water droplets or ice crystals are large enough to scatter the light of the seven wavelengths (red, orange, yellow, green, blue, indigo, and violet), which combine to produce white light.
Why are clouds dark?
The main reason why rain clouds are dark is due to their particulate density. As clouds are formed from minuscule water droplets and/or ice crystals, the denser they are packed, the more light radiating from the Sun is scattered and dispersed by them, lending a darker appearance to their lower sections.
The process by which energy incident on a surface is turned back at the same angle into the medium through which it originated.
Means stars twinkling.
Don't twinkle unless they are near horizon, too bright.
Scattering or Diffusion
The process by which light rays change direction of propagation thorugh the interation with particles, such as molecules, aerosols, and cloud particles.
Why is the sky blue?
More blue, shorter wavelengths are scattered by atmospheric gasses, longer red wavelengths pass right through and are not scattered.
Why are sunsets red?
Light from sun passes through more atmosphere, even more blue light is scattered allowing reds to go straight to your eyes.
Beams from of light from the sun caused by scattering of light of particles in the atmosphere such as aerosols.
When light passes though a substance it is transmitted. Denser materials slow the light and bend it.
When light is bended. Depends on material density and the angle light enters the medium.
Refraction causes light rays from the lower part of the sun or moon to bend more than the upper part, making them appear to ‘flatten out’.
Types of Twilight
Civil twilight lasts from Sunset till the sun is 6° below the horizon.
Astronomical Twilight lasts from sunset till the sky is completely dark and observation of the faintest astronomical stars is possible.
What causes the green flash?
the atmosphere acts as a weak prism, refracting light into various colors, green is the peak frequency emitted by the sun and is what gets through the atmosphere the most so we see a green flash.
Inferior Marriage, lower and upside-down
Superior, Objects upward but right side up.