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EASC 11 Chapters 14-18: The Atmosphere Fill in your note outline as you follow along with the Atmosphere…. 1. • 2. • 3. • 4. • What is “weather”? The state of the atmosphere at any given time What is “climate”? A generalized description of weather conditions in a region over a period of time What is “meteorology”? The science of studying Earth’s atmosphere and weather What is “atmosphere”? The envelope of air (gasses) that surrounds the earth; one of the four “spheres” of the earth EASC 11 • The most important basic elements of weather that are measured are: air temperature, humidity, type and amount of cloudiness, type and amount of precipitation, air pressure, and speed and direction of wind • Air is a variable mixture of components, mainly nitrogen and oxygen with small components of other gases such as argon; there is also a very small amount of carbon dioxide that is critical to the atmosphere • Air also contains water vapour; although it is a relatively small amount, it, too is very important EASC 11 • • • • Air also contains aerosols: very fine solid and liquid particles such as sea salt, smoke, soot, soil, pollen, volcanic ash and dust, chemicals, bacteria, and other pollutants Aerosols are important in the formation of clouds and fog, in blocking and absorbing sunlight, and in scattering light at sunrise and sunset; they also contribute to pollution such as smog Ozone (O3) is a form of oxygen different from what we breathe (O2), and high in the stratosphere forms a protective layer that shields Earth from much of the harmful UV (ultraviolet) radiation from the Sun Ozone is broken down in the presence of chlorofluorocarbons (CFCs), which used to be used as propellants in aerosol cans EASC 11 • • • • Ozone at the surface of the Earth is considered a pollutant About 50% of Earth’s atmosphere is within 5.6 km (3.5 miles) of the surface of the Earth, about 90% is within 16 km (10 miles) and 99.99997% is within 100 km (62 miles) Air pressure, the weight of air pressing down, is highest at sea level and decreases with altitude The atmosphere is divided into layers based on temperature changes EASC 11 Figure 1: Structure of the Atmosphere EASC 11 Thermosphere – temperatures rise (mesopause) Mesosphere – temperatures drop (stratopause) – temperatures rise to this point Stratosphere – strong steady winds & weather (tropopause) – temperatures drop to this point Tropopause – weather occurs here Ionosphere – layer of ionized particles makes radio wave transmission possible Ozonosphere layer of ozone EASC 11 • • • • The Sun is the source of nearly all the energy that drives Earth’s weather (and climate, even though the amount of the Sun’s radiation intercepted by Earth is very small) The surface of the Earth is not heated equally; this drives ocean currents and creates winds that attempt to redistribute heat from the warm equatorial areas to the cool polar areas The rotation (spinning of Earth on its axis) and revolution of Earth (around the Sun), as well as the fact the Earth is a sphere all have an impact on how solar radiation is received on the Earth The angle of incoming solar radiation changes throughout the seasons of the year EASC 11 • 1. 2. 3. • • Heat is transferred in the atmosphere by Conduction: heat is transferred by collisions between molecules – not very important in the atmosphere Convection: heat is transferred by circulation in fluids – this is critical in the atmosphere Radiation: heat is transferred as a wave – this is how solar energy reaches Earth; different wavelengths exist, such as visible light, infrared radiation, and ultraviolet radiation Temperature is a measure of the energy of molecules A thermometer is used to measure temperature EASC 11 • 1. 2. 3. 4. Temperature can be affected by different factors; latitude (distance from the equator) is a major factor controlling temperature, but it is not the only factor: Differential heating of land and water: land heats up more rapidly and to higher temperatures and cools more rapidly and to cooler temperatures than water Altitude: higher elevations generally experience lower temperatures than lower elevations Proximity to the sea: areas closer to the sea generally experience less variation in temperature, and areas far away from the sea generally experience more extreme variation in temperature Cloud cover: during the day, clouds tend to reflect incoming radiation, leading to cooler temperatures than if the sky was clear; at night, clouds tend to trap heat , leading to warmer temperatures than if the sky was clear EASC 11 Read “World Distribution of Temperature” on p. 399-400, and examine the figures shown: Figure 2a: World average temperatures in January EASC 11 Figure 2b: World average temperatures in July