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

5.01 Heating and Cooling of the Atmosphere MTPs: Vertical Structure Composition ICAO Standard Atmosphere Temperature Scales Atmospheric Properties Atmospheric Density Temperature Differences Heating and Cooling

Vertical Structure Troposphere Stratosphere 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

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

Vertical Structure

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

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

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

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

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

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

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

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

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%

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

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

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

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

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

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

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

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

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

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?

Soaring