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Major Forms of Condensation

Major Forms of Condensation. Cloud Fog Frost and Dew. What are the forms of condensation?. Differences between Forms of Condensation. Cloud, fog, frost and dew?? Cloud high in the sky fog near the surface of the earth frost and dew at the surface of the earth.

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Major Forms of Condensation

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  1. Major Forms of Condensation

  2. Cloud Fog Frost and Dew What are the forms of condensation?

  3. Differences between Forms of Condensation • Cloud, fog, frost and dew?? • Cloud high in the sky • fog near the surface of the earth • frost and dew at the surface of the earth

  4. Similar in Formation • Cooling (Temperature drops) • Air holds less water • RH increases • When RH = 100%, moisture released

  5. Frost at 22/12/1999

  6. FROST & DEW

  7. Frost again

  8. Dew at Spider Web

  9. What is the difference between Dew and Frost? • Dew: dew point > 0C • Frost: dew point  0 C

  10. FOG

  11. Radiation Fog (Conditions) • Clear sky • high RH • temperature inversion • calm and still air • presence of depression or hollow

  12. Advection Fog

  13. Advection Fog

  14. Frontal Fog

  15. Steam Fog

  16. Upslope Fog

  17. CLOUD

  18. Precipitation • Water droplets from condensation is very small in size – 0.1 mm • Raindrops are much larger – 0.5-2.0 mm • The main difference between condensation and precipitation is the size of water droplets

  19. Formation Processes • Air cooling • Condensation and cloud formation • Accumulation of moisture • The growth of cloud droplets

  20. Collision and Coalescence • In tropical and sub-tropical regions • Cloud top temperature : • warmer than -15oC • Turbulence Mixing : • Different size droplets move at different speeds • cumulonimbus

  21. Collision and Coalescence wake capture Fall in higher speed Large Water droplet Fall in lower speed Direct capture

  22. Ice-Crystal (Bergeron) Process • In higher latitudes (temperate regions) • Super-cooled water – water droplets in cloud with temperature below 0oC • Because of extremely small size of cloud droplets • Insufficient freezing nuclei

  23. Ice-Crystal (Bergeron) Process • Saturated vapour pressure over super-cooled water is greater than that over ice

  24. Ice-Crystal (Bergeron) Process • Air can be saturated for ice when it is not saturated for water

  25. Ice-Crystal (Bergeron) Process • Ice crystals grow at the expense of cloud droplets until they are large enough to fall

  26. 3 main types of precipitation Low pressure system due to thermal nature Warm air mass meets cold air mass Uplifting along slopes Tai Mo Shan ITCZ Polar front

  27. Spatial Variation of rainfall • There is more precipitation in ocean than in continent. ocean continent

  28. Spatial Variation of rainfall • Primary maximum occurs at a belt between 10oN to 10oS in the vicinity of the ITCZ ocean continent

  29. Spatial Variation of rainfall • secondary maximum occurs at a belt between 40o to 55oN&S in the vicinity of the ITCZ ocean continent

  30. Spatial Variation of rainfall • Primary minima find in latitudes higher than 55oN&S • Secondary minima in sub-tropical high pressure belts (20o-35oN&S) ocean continent

  31. Factors affecting the pattern of rainfall • Air pressure • Zones of convergence and divergence • Strong convection along low pressure belts • Uprising air leads to condensation and cloud formation • Descending air along high pressure belts suppress condensation

  32. 50oN 0o 50oS • Describe and explain the factor that influence the pattern of rainfall from the diagram on the right.

  33. Zones of abundant rainfall • Around the equatorial regions • e.g. Amazon Basin • Doldrum low pressure • Convergence of trade winds along ITCZ • Intense solar radiation promotes strong convective uplift • Ares dominated by warm moist equatorial marine air masses

  34. Zones of abundant rainfall • Western sides in middle latitudes • e.g. Western Coast of Canada • Under influences of the onshore westerlies and frequent frontal cyclones • Western mountrains(Rockies and Andes) promote orographic influences and heavy precipitation

  35. Describe and explain the factor that influence the pattern of rainfall from the diagram on the right.

  36. Zones of scanty rainfall • Polar areas of North America • Air with low moisture content due to low temperature • Descending cold upper air masses unfavourable for condensation

  37. Zones of scanty rainfall • 15o-30oS in the western side of South America • 30o-40oN of south-western U.S.A. • Affected by sub-tropical anticyclone of high pressure • Rain-shadow effect of Rockies and Andes

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