1. Ground School: Meteorology
5.03 Moisture
References: -Transport Canada Study and Reference Guide Pilot - -FTGU pages ,
Instructor
40 Minutes

2. Ground School 5.03 Meteorology - Moisture
MTPs:
Relative Humidity and Dew Point
Changes of State
Cloud Formation
Precipitation
ICAO Lapse Rates

3. Ground School 5.03 Meteorology - Humidity
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. Ground School 5.03 Meteorology - Humidity
The warmer the air, the more water vapour it can hold...Why?
-Warm air can hold much more moisture (water vapour) than cold air. For example, one kilogram of dry air at 30c can hold 30 grams of water vapour before it becomes saturated. One kg of dry air at 0c can hold only 5gms of water vapour before it is saturated. This is because one kg of warm air has a much greater volume than one kg of cold air, thus allowing it to hold a greater quantity of water vapour.
1 kg air at 0 degrees
= 5g water
1 kg air at30 degrees
= 30g water

5. Ground School 5.03 Meteorology - Humidity
Example
If we took a parcel of air at 10oC at 100% relative humidity and warmed it up, how would the relative humidity change?

6. Ground School 5.03 Meteorology - Humidity
Questions:
1. Define Relative Humidity.
The ratio of water present in the air compared to the amount the same volume could hold if it were saturated
2. Define Dew Point
Temperature to which air must be cooled at constant pressure to become saturated

7. Ground School 5.03 Meteorology – Changes of State
Freezing
Evaporation
Melting
Sublimation
Condensation

8. Freezing Melting Evaporation Sublimation WATER ICE Sublimation
SOLID
LIQUID
Melting
WATER
ICE
Evaporation
Sublimation
Sublimation
Condensation
GAS
Review diagram.
Some everyday examples of these processes are;
Clouds forming = Condensation.
Freezing = Ice.
Sublimation = Hoar frost
Sublimation = Hoar frost dissipates
Melting = Ice/Snow to water
Evaporation = Lakes, Rivers lowering etc.
QTC: Can you think of any any other examples?
WATER VAPOUR

9. Ground School 5.03 Meteorology – Changes of State
Questions:
1. What do you call a change of state from liquid to solid?
Freezing
2. From solid to gas?
Sublimation
3. From vapour to liquid?
Condensation

10. What kind of cloud?
Cloud Formation

11. Ground School 5.03 Meteorology – Cloud Formation
Invisible water vapour becomes visible as water droplets or ice
Condensation of water vapour

12. Ground School 5.03 Meteorology – Cloud Formation
What is required:
High relative humidity
Condensation nuclei
Cooling of the air
Cold surface
Adiabatic cooling

13. Ground School 5.03 Meteorology – Cloud Formation
Steps
Air is heated and rises
Air cools to point of saturation
Air condenses onto condensation nuclei

14. Ground School 5.03 Meteorology – Cloud Formation
Question
What are the three things required for cloud formation?
High relative humidity
condensation nuclei
cooling of the air

15. Precipitation

16. Ground School 5.03 Meteorology – Precipitation
Water droplets grow in size and weight and fall due to gravity
Can also occur below freezing (water vapour and ice crystals)
The average rain drop is a million times larger than a cloud water droplet

17. Ground School 5.03 Meteorology – Precipitation
If the cloud is…..
Below freezing – joining of ice crystals
Above freezing = rain
If temp below is cold enough to allow crystals to fall to ground = snow

18. Ground School 5.03 Meteorology – Precipitation
Regions of a cloud
Snow
Rain and/or snow
Rain
Large drops and heavy rain = strong vertical motion

19. Ground School 5.03 Meteorology – Precipitation
Types of precipitation
Drizzle
very small drops of water which appears to float
Rain
Large water droplets

20. Ground School 5.03 Meteorology – Precipitation
Hail
Hard transparent layer of ice covering soft white core
Snow Grains
Tiny snow crystals that have acquired a coating of rime

21. Ground School 5.03 Meteorology – Precipitation
Snow Pellets
Soft white ice (hail without hard transparent layer
Snow
Agglomeration of ice crystals hexagonal/star shaped

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

23. Online Ground School 5.03 Meteorology – Precipitation
Question
What are the 8 different types or precipitation?

24. Online Ground School 5.03 Meteorology – ICAO lapse rate
Rate of decrease in temperature with altitude

25. Ground School 5.03 Meteorology – ICAO lapse rate
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
Dry Adiabatic
3.0 °C / 1000 ft
Saturated Adiabatic
1.5° C / 1000 ft
Standard
2.0 °C / 1000 ft
ICAO
1.98 °C / 1000 ft

26. Ground School 5.03 Meteorology – ICAO lapse rate
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

27. Ground School 5.03 Meteorology – ICAO lapse rate
Inversion
Increase in temperature with altitude
Isothermal Layer
Layer in which temperature remains the same

28. Ground School 5.03 Meteorology – Confirmation
1. What is the dry adiabatic lapse rate?
_____ degrees per _________feet
2. What is hail?
Hard transparent layer of ice covering soft white core
3. A parcel of air has a relative humidity of 50%. If the temperature were to decrease how would the relative humidity change?