1. Clouds

2. Water is strange stuff! Gas - water vapour (invisible) Liquid - water droplets (visible) Solid - ice crystals, hail, snow Water can occur in 3 states:

3. What are clouds? Clouds are formed of tiny droplets of water or ice. Clouds form when water vapour cools and condenses. The temperature at which condensation occurs is called dew point. Condensation also requires nucleii (small particles) such as dust.

4. What happens when air is cooled? Relative humidity increases. Dew point is reached (100% relative humidity). Water vapour (invisible) condenses to form water droplets (visible). Sometimes the water vapour may change straight into solid state: called sublimation.

5. Localized convective lifting occurs where unequal surface heating causes pockets of air to rise because of their buoyancy.  Localized Convective Lifting

6.  Convergence Convergence is when air flows together and rises. Processes that lift air Cloud Formation

7. Orographic Lifting Orographic lifting occurs when mountains act as barriers to the flow of air, forcing the air to ascend. The air cools adiabatically; clouds and precipitation may result.

8. Cloud Formation When air is allowed to expand, it cools, and when it is compressed, it warms.  Adiabatic Temperature Changes Dry adiabatic rate is the rate of cooling or heating that applies only to unsaturated air.  Expansion and Cooling Wet adiabatic rate is the rate of adiabatic temperature change in saturated air. Air Compression and Expansion

9. Cloud Formation by Adiabatic Cooling

11. Cloud Formation A front is the boundary between two adjoining air masses having contrasting characteristics.  Frontal Wedging Processes That Lift Air

12. Cloud Types and Precipitation  Clouds are classified on the basis of their form and height. Cirrus (cirrus = curl of hair) are clouds that are high, white, and thin. Cumulus (cumulus = a pile) are clouds that consist of rounded individual cloud masses. Stratus (stratus = a layer) are clouds best described as sheets or layers that cover much or all of the sky. Types of Clouds

13. Clouds can be classified by their shape and height Flat clouds eg Stratus (St) Fluffy clouds eg Cumulus (Cu) Wispy clouds eg Cirrus (Ci) Cloud shapes

14. Clouds can also be classified by height of cloudbase Low level (below 2000m) eg stratus Middle level - alto (2,000 to 6, 000m) eg alto-cumulus High level - cirro (above 6,000m) eg cirrus Cloud heights

15. Cloud Classification

16. Spot the cloud! Low and flat ….. Stratus

17. Spot the cloud! Middle level, fluffy ….. Alto -Cumulus

18. Spot the cloud! High level, wispy ….. Cirrus

19. Spot the cloud! Rain bearing, storm clouds ….. Cumulo-Nimbus

20. World cloud patterns Can you explain the major world cloud belts?