1. Cloud and Precipitation Notes

2. Water Cycle Most of the Earth’s water is recycled
Oceans hold most of the water
Evaporation: The change of state from a liquid to a gas
Condensation: The change of state from a gas to a liquid
Precipitation: Water falls from clouds to the earth

3. How are clouds formed? Made of condensed water vapor
Air cools as it rises and condenses into tiny droplets or ice crystals
These tiny droplets/ice crystals are so light they either float as clouds or fall very slowly
Water must condense on something solid (Ex. dust, smoke, salt, etc.)

4. Characteristics of clouds
Form under different conditions
Shapes and sizes are determined by air movement
Location is also a factor
Higher altitude = tiny crystals
Lower altitude = water droplets/ice crystals

5. 3 Main Types of Clouds
Cirrus
Cumulus
Stratus

6. Two prefixes that help to describe clouds further are:
Nimbo/nimbus
Produce precipitation
Alto
Medium altitude

7. Cirrus Clouds Means “curl of hair”
Form at high altitudes in very cold air
It is made of ice
Wispy or feathery in appearance
Normally found in fair weather but can be a sign that a storm is approaching

8. Cumulus Clouds Means “heap” or “pile”
Puffy white clouds with darker bases
Usually appear in the daytime
Cooler air sinks along the sides of these clouds keeping them apart
Cumulonimbus clouds are ones that produce thunder storms, they are also called thunderheads

9. Stratus Clouds Means “spread out”
These are the clouds that produce ‘grey’ skies
They form in flat layers when air cools over large area without rising
They are smooth because they form without strong air movement

11. Fog A cloud that rests on the ground or a body of water
If forms when a surface is colder than the air above it
Heaviest at dawn
It can be a safety hazard while driving because it makes it hard to see what is in front of you

12. What is precipitation?
Any form of water that falls from the clouds and reaches Earth’s surface
Cloud droplets are much smaller than a typical raindrop
Precipitation always comes from clouds but not all clouds form precipitation
What types of clouds do?

13. Formation
Cloud droplets (water) or ice crystals must grow heavy enough to fall through the air.
They get heavier by colliding or combining with other droplets.

14. Measuring Precipitation
Rain Gauge
Measuring snow
Rain gauge - open ended tube or can that collects rainfall in a container. The container usuallly has markings on it or a ruler is used
Snow - use a ruler in the snow or melting snow collected in a container.

15. Types of Precipitation
Rain
Sleet
Freezing Rain
Snow
Hail

16. Rain
Most common form
.5mm in diameter
Fall from nimbostratus clouds

17. Rain

18. Sleet When there are layers of warm air and cold air in the sky.
As droplets fall they freeze into solid ice particles

19. Sleet

20. Freezing Rain
Raindrops falling through cold air that don’t freeze until they reach a cold surface (the ground)
Looks like sleet as it falls but freezes on the surface instead of right before it hits the surface

21. Freezing Rain

22. Freezing Rain vs. Sleet
Smaller the cold area closest to ground is freezing rain (less time to refreeze)
What is the difference between the two pictures?
Which is freezing rain and which is sleet? WHY?

23. Snow Ice crystals grow and merge to form snowflakes
Variety of shapes and sizes
Most have 6 sides or branches
When they fall through moist air that is near freezing they clump together
When falling through colder drier air they don’t

24. Hail Only forms inside cumulonimbus clouds
Strong updrafts carry the ice pellets up and down causing the pellet to get bigger
When it gets to heavy it falls to the ground

25. Hail

27. Acid Rain
Forms when factories, power plants, automobiles and some natural sources release sulfur dioxide and nitrogen oxides into the air
They combine with the water to form sulfuric acid and nitric acid
This acid rain can affect trees, lakes and damage the surface of buildings and sculptures

28. Acid Rain damage

29. How Acid Rain Forms