10.2 Energy Transfer in the Atmosphere

1. 10.2 Energy Transfer in the Atmosphere • Originally, Earth’s atmosphere had no oxygen. • Scientists think it came from the breakdown of water by sunlight, then from photosynthesis by plants. • The density of the atmosphere decreases with altitude. The composition of Earth’s atmosphere

2. The Layers of the Atmosphere 1)The Troposphere: - closest to Earth’s surface - highest density layer because all other layers compress it - contains almost all the water vapour in the atmosphere. • so, this is where most weather takes place. • 2nd warmest layer See pages 438 - 439

3. The Stratosphere: • the second layer • warming from –55ºC as altitude increases • The air is cold, dry, and cloudless. • Strong, steady winds, planes often fly here to avoid turbulent troposphere. • The ozone layer is found here, which blocks harmful UV radiation.

4. The Upper Atmosphere • The mesosphere: (3rd layer) • Temperatures are as low as –100ºC • This layer is where space debris burns up when it begins to hit particles. • The thermosphere: (4th layer) • Temperatures can reach +1500ºC to +3000ºC because of radiation from the sun • This is where the Northern Lights, aurora borealis, are found. • The exosphere: (5th layer) • where the atmosphere merges with outer space. The layers of Earth’s atmosphere

5. Radiation and Conduction in the Atmosphere • Thermal energy mostly comes from the Sun. • the most is transferred at the equator • Insolation = amount of solar radiation • decreases with dust, smoke, pollution,etc. or if the angle of incidence of the solar radiation is too great. • Solar radiation does not heat the atmosphere directly. • Earth’s surface absorbs it, heats up, and then radiates the energy into the atmosphere. • Convection currents spread the energy around. Angle of incidence

6. Albedo Not all of the solar radiation that hits earth stays in our atmosphere, some is reflected back into space! • Albedo refers to the amount of energy reflected by a surface. • Light-coloured surfaces (snow, sand) have a high albedo and reflect energy. • Dark-coloured surfaces (soil, water) have a low albedo and absorb energy.

7. What Is Weather? • Weather is the atmosphere conditions. • Atmospheric pressure is determined by the number of molecules and how fast they are moving. • measured with a barometer • measured in kilopascals (kPa) • Ex. our ears pop with pressure change • as you increase altitude, the pressure drops • warm air is lighter and less dense than cool air so warm air has a lower pressure than cool air Atmospheric pressure exerts force on you from all directions.

8. Humid air (air with more water vapour) has lower pressure than dry air. • Dew point = the temperature where no more water vapour can be held by air • Relative humidity = the percentage of the air that is currently holding water vapour

9. Convection in the Atmosphere • Wind is the movement of air from higher pressure to lower pressure. • An air mass is a large body of air with similar temperature and humidity. • takes on the conditions of the weather below.

10. High pressure systems form when an air mass cools. • winds blow clockwise around the centre of the system. • usually brings dry weather • Low pressure systems form when an air mass warms. • winds blow counterclockwise around the centre of the system. • usually bring wet weather.

11. Prevailing Winds • are winds that are typical for a location. • Winds in B.C. usually blow in from the ocean. • Precipitation falls as air is forced up the mountains • So air gets drier as it moves inland • Dry air rushes down the far side of the mountains into the prairies. The prevailing winds off British Columbia’s coast, crossing into Alberta.

12. The Coriolis Effect • Winds move from higher pressure to lower pressure. • air warms in the tropics and rises • cooler air from the north fills the empty space • this occurs at several latitudes • As Earth rotates, these winds are “bent” clockwise = Coriolis effect • The equator moves much more quickly than do the poles. • Air rotates counterclockwise in the northern hemisphere and clockwise in the south.

13. Jet Streams = strong winds occurring in areas between high and low pressure systems in the upper troposphere • The polar jet stream can move at 185 km/h for thousands of kilometres. • Planes flying east across Canada “ride” the jet stream and avoid it flying west.

14. Local Winds, and Fronts • are influenced by local geography. • In British Columbia, sea breezes blow inland when the land warms in the morning and outward when the land cools in the evening. • a front is a boundary between two different air masses. • cold air forces warm air to rise, so fronts usually bring precipitation.

15. Extreme Weather • Air masses have very large amounts of thermal energy. • Extreme weather occurs when this energy is released. • Thunderstorms occur when warm air rises and water condenses • Static energy can be built up and released as lightning. • Sea breezes in the tropics and energetic cold fronts can cause thunderstorms.

16. Tornadoes Vs. Hurricanes • Tornadoes form when thunderstorms meet fast horizontal winds. • A “funnel” of rotating air may form, which sometimes extends all the way to the ground with winds of up to 400 km/h. • Hurricanes = tropical cyclones = typhoons • occur at the tropics, with their intense heat • Large masses of warm, moist air rise quickly and cool air rushes in. Take the Section 10.2 Quiz