10.2 Energy Transfer in the Atmosphere

Transcription

1 10.2 Energy Transfer in the Atmosphere

2 Learning Outcomes Understand the different layers of the atmosphere Understand how energy moves in, out, and around our atmosphere

3 er Composi<on of the Atmosphere

4 Atmosphere Origins Originally, Earth s atmosphere had no oxygen. Scientists think it first came from the breakdown of water by sunlight, then from photosynthesis by plants and/or cyanobacteria.

5 Density of Atmosphere The density of the atmosphere decreases with altitude

6 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. 2 nd warmest layer See pages

7 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.

8 The Upper Atmosphere The mesosphere: (3 rd layer) Temperatures are as low as 100ºC This layer is where space debris burns up when it begins to hit particles. The thermosphere: (4 th 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: (5 th layer) where the atmosphere merges with outer space. The layers of Earth s atmosphere

9 Radiation and Conduction in the Atmosphere Thermal energy mostly comes from the Sun. Most thermal energy is transferred near the equator, which receives a more direct source of solar radiation. Insolation = amount of solar radiation an area receives, measured in W/m 2 decreases with dust, smoke, pollution, etc. or if the angle of incidence of the solar radiation is too great. Angle of incidence

10 Solar radiation does not heat the atmosphere directly. Earth s surface absorbs solar radiation, heats up, then radiates the thermal energy into the atmosphere (as infrared) Convection currents in the air spread the thermal energy around.

11 The Radiation Budget The radiation budget is used to explain where all of the solar radiation that reaches Earth actually goes. Earth s radiation budget = heat gained heat lost

12 Albedo 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.

13 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 throughout. takes on the conditions of the weather below. can be as large as an entire province or even larger.

14 High pressure systems form when an air mass cools. This usually occurs over cold water or land. Winds blow clockwise around the centre of the system. Low pressure systems form when an air mass warms. This usually occurs over warm water or land. Winds blow counterclockwise around the centre of the system. Lows usually bring wet weather.

15 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. See pages

16 The Coriolis Effect Winds move from higher pressure to lower pressure. In a simple model, air would warm in the tropics and rise. Cooler air from the north would rush in below to fill the empty spot. The warm air at higher altitudes would move north to replace the cooler air. This occurs at several latitudes as we move north. As Earth rotates, these winds are bent clockwise = Coriolis effect The equator moves much more quickly than do the poles.

17 Jet Streams Strong winds occur in areas between high and low pressure systems. The boundaries between the global wind systems have very strong winds. In the upper troposphere, between warm and cool air, are the jet streams. 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.

18 Local Winds, and Fronts Local winds arise and 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.

19 Extreme Weather Air masses often have very large amounts of thermal energy. Extreme weather can arise as this energy is released. Thunderstorms occur when warm air rises and water condenses (which releases even more energy), building the thunderhead even higher. Static energy can be built up and released as lightning. Sea breezes in the tropics and energetic cold (and even warm) fronts can cause thunderstorms. See pages

20 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. The tropics, with their intense heat, can often have severe weather. Large masses of warm, moist air rise quickly and cool air rushes in. Air rotates counterclockwise in the northern hemisphere, clockwise in the south. Hurricanes = tropical cyclones = typhoons

21 Homework Page 459 #1 5, 12-19