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GPS NGS: Meteorology. 405.03 Moisture. References : -A-CR-CCP-242/PT-005 Chapter 2 -Transport Canada Study and Reference Guide Glider Pilot - -FTGU pages 135-138, 146-147. Instructor. 40 Minutes. 405.02 Moisture. MTPs: Relative Humidity and Dew Point Changes of State Cloud Formation

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  1. GPS NGS: Meteorology 405.03 Moisture References:-A-CR-CCP-242/PT-005 Chapter 2 -Transport Canada Study and Reference Guide Glider Pilot - -FTGU pages 135-138, 146-147 Instructor 40 Minutes

  2. 405.02 Moisture • MTPs: • Relative Humidity and Dew Point • Changes of State • Cloud Formation • Precipitation • ICAO Lapse Rates

  3. MTP: Relative Humidity and Dew Point • Relative Humidity • Ratio of water present in air compared to the amount the same volume could hold if it were saturated • Dew Point • Temperature to which air must be cooled at constant pressure to become saturated

  4. MTP: Relative Humidity and Dew Point • The warmer the air, the more water vapour it can hold...Why? 1 kg air at 0 degrees = 5g water 1 kg air at30 degrees = 30g water

  5. MTP: Relative Humidity and Dew Point • Define Relative Humidity. • The ratio of water present in the air compared to the amount the same volume could hold if it were saturated • Define Dew Point • Temperature to which air must be cooled at constant pressure to become saturated

  6. MTP: Changes of State • Freezing • Evaporation • Melting • Sublimation • Condensation

  7. Freezing SOLID LIQUID Melting ICE WATER Evaporation Sublimation Sublimation Condensation GAS WATERVAPOUR

  8. MTP: Changes of State • What do you call a change of state from liquid to solid? • Freezing • From solid to gas? • Sublimation • From vapour to liquid? • Condensation

  9. Cloud Formation

  10. MTP: Cloud Formation • Invisible water vapour becomes visible as water droplets or ice • Condensation of water vapour

  11. MTP: Cloud Formation • What is required: • High relative humidity • Condensation nuclei • Cooling of the air • Cold surface • Adiabatic cooling

  12. MTP: Cloud Formation • What are the three things required for cloud formation? • High relative humidity • condensation nuclei • cooling of the air

  13. Precipitation

  14. MTP: Precipitation • Water droplets grow in size and weight and fall due to gravity • Above freezing – coalescence due to vertical currents • Can also occur below freezing (water vapour and ice crystals) The average rain drop is a million times larger than a cloud water droplet

  15. MTP: Precipitation • Below freezing – aggregation of ice crystals • If below cloud is above freezing = coalesce and rain • If temp below is cold enough to allow crystals to fall to ground = snow

  16. MTP: Precipitation • Regions of a cloud Aggregation Aggregation and coalescence Coalescence Large drops and heavy rain = strong vertical motion

  17. MTP: Precipitation • Drizzle • very small drops of water which appears to float • Rain • Large water droplets

  18. MTP: Precipitation • Hail • Hard transparent layer of ice covering soft white core • Snow Grains • Tiny snow crystals that have acquired a coating of rime

  19. MTP: Precipitation • Snow Pellets • Soft white ice (hail without hard transparent layer • Snow • Agglomeration of ice crystals hexagonal/star shaped

  20. MTP: Precipitation • Ice Prisms • Tiny ice crystals in the form of needles • Ice Pellets • Formed by freezing of raindrops

  21. MTP: Precipitation • What are the 8 different types or precipitation? • Drizzle • Rain • Hail • Snow • snow grains • snow pellets • ice pellets • ice prisms

  22. MTP: ICAO Lapse Rates • Lapse rate • Decrease in temperature with altitude • Inversion • Increase in temperature with altitude • Isothermal Layer • Layer in which temperature remains the same

  23. MTP: ICAO Lapse Rates • Lapse rates: • Recall ICAO Standard Atmosphere: • Air is perfectly dry gas • Mean sea level pressure of 29.92 • Mean sea level temp of 15°C

  24. MTP: ICAO Lapse Rates • Can determine base of clouds: • Temperature on ground 10 degrees • Dew point 7 degrees • Lapse Rate Saturated adiabatic (1.5/1000 ft) • Cloud base = 2000 feet

  25. 405.03 Confirmation • What is the dry adiabatic lapse rate? • 3 degrees per 1000 feet • What is hail? • Hard transparent layer of ice covering soft white core • In temperatures above freezing, rain is formed by the _________ of water droplets • Coalescence

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