Meteorology

1. Meteorology 5.01 Heating and Cooling of the Atmosphere References: FTGU pages 123, 124, 136 and 137

2. 5.01 Heating and Coolingof the Atmosphere • MTPs: • Vertical Structure • Composition • ICAO Standard Atmosphere • Temperature Scales • Atmospheric Properties • Atmospheric Density • Temperature Differences • Heating and Cooling

3. Vertical Structure • Troposphere • Weather happens here • To 25,000 – 30,000 feet over poles • To 55,000 – 65,000 feet over equator • Temperature decreases with height • Stratosphere • Troposphere to 170,000’ • Temperature increases with height

4. Vertical Structure • Mesosphere • Stratosphere to 270,000’ • Temperature decreases with height, to -85°C • Thermosphere • Tops at 1.1 million to 2.6 million feet (350-800 kilometres) • Temperature increases with height, up to 1,500°C • Exosphere • Mainly comprised of hydrogen and helium • Extends into space

5. Vertical Structure

6. Vertical Structure • Label the layers of the atmosphere! • Choose from these: • Stratosphere • Thermosphere • Exosphere • Troposphere • Mesosphere

7. Composition • The atmosphere is made up of a mixture of gases • Nitrogen (78%) • Oxygen (21%) • Other (~1%) (Argon, CO2, Water Vapour etc.) • Although water vapour is less than 1% of the atmosphere, it remains the most important component from the standpoint of weather, based especially on its ability to change state

8. ICAO Standard Atmosphere • The International Civil Aviation Organization (ICAO) Standard Atmosphere: • Sea Level for North America • Based on summer and winter averages at 40°N latitude • The Standard: • MSL pressure of 29.92” Hg (1013.25 hpa) • MSL temperature of 15°C • Air is a “perfectly dry gas” • Lapse rate of 1.98°C per 1000 feet

9. Temperature • Sun heats earth, earth heats atmosphere • Celsius (nearly worldwide): • Freezing point of water: 0°C • Boiling point of water: 100°C

10. Atmospheric Properties • Mobility • The ability for air to move • Atmosphere like an “ocean of air” • Wind like “streams of water” • (Much more freedom of movement with air than water) • Compression • Air is compressed as it descends into greater pressure • Occupies less space

11. Atmospheric Properties • Expansion • As air rises, it reaches areas of lower pressure, causing it expand and cool • This cooling can be enough to condense water vapour in the air, forming cloud • This is why clouds and precipitation are common in areas of rising air • From a meteorological standpoint, the most important property of the air! • www.youtube.com/watch?v=Li9eyds1Y_g

12. Atmospheric Properties Density - mass per unit volume • Cold air is dense: • Molecules are move slowly and are packed close together • Heavier and tends to sink • Warm is less dense: • Molecules are moving rapidly taking up more space (or less molecules in the same space) • Warm air is lighter and is pushed up by the cold air

13. Atmospheric Density • Density Relationships: • Density vs. Temperature: • Indirectly proportional • Density vs. Humidity: • Indirectly proportional • Density vs. Pressure: • Directly proportional

14. Confirmation • Questions • 1. What is the most important property of the atmosphere? • 2. If the density of the air increases, what happens to the pressure? • 3. What gas makes up the majority of the atmosphere? • Nitrogen 78%

15. Temperature Differences • Horizontal Temperature Differences • Diurnal Variation • Seasonal Variation – earth’s tilt • Latitude- north pole versus equator • Topography • Land and water differences • Clouds • Clouds reflect large amounts of solar radiation • At night, clouds trap the heat radiated off the earth

16. Atmosphere Heating • Types of Atmospheric Heating: • Radiation (heating) • Earth absorbs sun’s short wave radiation • The lower atmosphere is then heated by the earth

17. Atmospheric Heating • Conduction • If two substances are in contact, heat will flow from the warmer to the colder substance • Air is a poor conductor, so this usually only occurs in small layers • Same as the heat transferred when roasting marshmallows

18. Atmospheric Heating • Convection • Air heated through conduction becomes buoyant and rises • This air then heats the air in the upper atmosphere

19. Atmospheric Heating • Advection (heating) • Occurs when cold air moves over a warm surface and its lower layer is heated by conduction

20. Atmospheric Heating • Turbulent Mixing • Turbulent air mixes a warmer surface layer of air with an unheated air aloft, spreading the heat upward

21. Atmospheric Heating • Compression • As air descends it compresses due to increased pressure and therefore heats up

22. Atmospheric Cooling • Advection cooling • Lower levels only • When air is cooled by moving over a colder surface • Cooling occurs as a result of conduction between air and surface • Some mechanical turbulence can aid in spreading cooling effect

23. Atmospheric Cooling • Expansion cooling • The most important cooling process of the air • Air forced to rise experiences lower pressure and is allowed to expand • This expansion causes decrease in temperature

24. Confirmation Questions • Name 2 types of atmospheric heating • Name 2 types of atmospheric cooling • Describe how the earth is heated and cooled through radiation. • Which layer of the atmosphere contains all weather?

25. Soaring