1. Factors that affect weather
Air pressure, humidity, temperature, precipitation

2. The Water Cycle Take out a clean sheet of paper.
Number your paper 1-7 leaving half of the page for a picture.
Write the 7 definitions on the following slide.
Wait for Mrs. Couch to draw the picture (Yes you have to draw the picture)

3. The Parts of the Water Cycle
Evaporation
Condensation
Precipitation
Deposition
Sublimation
Infiltration
Percolation
Surface Run off
Transpiration
Urination
Accumulation

4. Important parts of the water cycle
Evaporation – liquid to gas
Condensation – gas to liquid
Precipitation – any form of water falling from the clouds to the ground
Transpiration – plant sweat
Surface Run off – water moving over land from higher to lower ground
Infiltration – Water fills the space between particles of soil

5. The water cycle – cont.
Percolation – Ground water moving below earth’s surface
Accumulation – a big pile of water, pond, puddle, ocean, river etc.
Urination – liquid waste – yuk
Sublimation – Water vapor freezes into a solid – makes snow
Deposition – Solid that vaporizes – skips the liquid phase

6. Humidity

7. Humidity and Relative Humidity
Humidity – the amount of water vapor in the atmosphere
Relative Humidity = The actual amount of water vapor in the air divided by the maximum amount of water vapor the air can hold

8. Measured with A sling psychrometer Made of 2 thermometers A wet bulb
A dry bulb

9. How it works 2 – the wet bulb is cooled by evaporation
1 – sling it over your head for 20 seconds so air blows over the thermometers
2 – the wet bulb is cooled by evaporation
3 – therefore the temperature of the wet bulb is < the dry bulb
4 – use the chart to compare the temperatures

10. Dew Point
Dew Point = The temperature at which air would have to cool to reach saturation (all of the water vapor it could hold)
The dew point will never be greater than the temperature!!
BUT if it is equal – humidity = 100% - causes condensation  fog, clouds, precipitation
Check out the Dew point Calculator!

11. How do clouds form? Remember:
**Warm air holds more water than cold air
**As air rises it cools
Condensation:
occurs when there is enough water vapor in the air
tiny particles must be present for the water to stick to
Dew Point:
The temperature at which condensation occurs
Clouds form when warm air rises and the water vapor the air holds is cooled to the dew point
Let’s put this in your own words!!!

12. Important Cloud Vocabulary
Cirro – curly or whispy
Nimbus – rain
Stratus - layer
Alto – middle
Cumulo - heaped

13. 3 Ways to Identify Clouds
Altitude
Shape
The weather they bring
Let’s look at some examples:

14. Cumulo (heap/pile)
Fair weather
2 – 18 km

15. Cirrus (curly/whispy)
Above 6 km – very high in the sky
Made of ice crystals

16. Stratus (layer – spread out)
Cover all or most of the sky
Thicker – brings rain/snow/drizzle

17. Other Clouds Nimbo – Rain Alto – middle 2 – 6 km
Fog – stratus clouds low to the ground
Cumulonimbus – Thunderheads
Contrails – Jet trails

19. Factors that affect weather
Air pressure, humidity, temperature, precipitation

20. Remember … Air has mass and takes up space.
Air pressure – the mass of the air being pulled down on an area of the earth’s surface.
It pushes in all directions - it does not crush objects

21. 2 things that affect air pressure
Temperature
The amount of air above it

22. Air moves?
Yes – air moves from areas of high pressure to low pressure quickly

23. Weather Indicators Falling Air Pressure Storms Rising Air Pressure
Good Weather

24. Measuring Air Pressure – Barometer
Mercury - glass tube open at the bottom In a glass dish of mercury
Measured in inches
Aneroid Barometer – air tight metal chamber
The wall flex in and out with the changes in air pressure.
Measured in millibars
1 inch = mb

25. Cheat sheet
Elevation
Pressure
Pressure
Density

26. Precipitation

27. Any form of water that falls from the clouds to the ground
What is precipitation?
Any form of water that falls from the clouds to the ground

28. Rain The most common Must be at least .5mm in diameter
Any smaller =mist or drizzle
Which falls from nimbostratus clouds

29. Sleet Occurs when rain falls through a layer of air below freezing
Freezes into solid ice before it hits the ground
Smaller than 5 mm

30. Freezing Rain
Falls as rain and freezes when it touches a surface below freezing
Does not freeze in the air

31. Hail Ice > than 5 mm in diameter ONLY from cumulonimbus clouds
Adds layers from up and down drafts in the cloud
Can damage property

32. Snow
Water vapor that turns directly into ice (not frozen liquid water)
Each snowflake has six sides and is different

33. How is it measured?
Liquid Precipitation – rain is measured with a rain gauge
Snow is measured with a ruler

34. Long periods of unusually low precipitation
Drought
Long periods of unusually low precipitation

35. Other Terms: Drought: long period of low precipitation
Cloud Seeding: dropping tiny crystals of dry ice (solid CO2) and silver iodide sprinkled into clouds from planes. May be used to clear fog at airports.