1. Chapter 22 The Atmosphere

2. Characteristics of the Atmosphere Layers of the Atmosphere –Several layers: differ in temperature, in density, and in the relative amounts of the different gases –Gases in the atmosphere: Nitrogen: 78% Oxygen: 21% Trace gases: 1%

4. Characteristics of the Atmosphere

5. We live in the Troposphere: –Layer closest to the Earth surface –Densest layer (gases above pushing down) –Most weather occurs here –Gets cooler with higher altitude –Lower region warmer because of the radiation and conduction of solar energy warming the Earth’s surface –Top of the troposphere is the tropopause: Poles: 8km (5mi) Equator: 18km (11mi) Temperature: -55 0 C This low temperature keeps water vapor in the troposphere Acts like a lid keeping water vapor in –Clouds, rain, snow

6. Characteristics of the Atmosphere Troposphere: –Upper region: cool air –Lower region: warm air –Temperature inversion: cool air gets trapped beneath warm air Can trap pollutants –Not healthy

14. Characteristics of the Atmosphere Stratosphere gets warmer with increasing altitude –Cold, low pressure –From near the top of the tropopause of about 25km (16 mi), the temperature is about -55 0 C (-67 0 F) to about 25km the temperature increases to approximately 0 0 C (32 0 F) in the stratosphere –Top is about 50km (31mi) –Gets warmer –Little water vapor (few clouds: no storms)

15. Characteristics of the Atmosphere Stratosphere: –The increase in temperature in the upper region occurs in the atmospheric layer known as the ozone layer Warmer because it contains a layer of oxygen known as ozone that absorbs solar radiation –Ozone absorbs much of the Sun’s UV radiation –Shields living organisms on Earth from ultraviolet- radiation damage

25. Characteristics of the Atmosphere In the stratosphere (at altitudes of 15 to 35 km) the ozone layer acts as a natural filter absorbing most of the sun's damaging ultraviolet rays - those that burn skin and cause some forms of skin cancer. Hence the concern about the depleting ozone layer in the earth's upper atmosphere. CFCs (chlorofluorocarbons) refrigerant and in spray cans has been shown to damage the ozone layer

26. Characteristics of the Atmosphere At ground level, ozone is a major component of photochemical smog which has a noticeable light brown color and results in reduced visibility and health concerns. The term smog has been in use since 1905 when it was used to describe the smoke and fog in many Scottish cities. In the 1940s increased concentrations of ground-level ozone were observed in Los Angeles. The concern with tropospheric or ground-level ozone is its very presence, because as a component of smog it is a serious pollutant.

33. Characteristics of the Atmosphere Mesosphere: –50 to 80km (31 to 50mi) –Temperature begins to fall as you go up –Top: -80 0 C (-112 0 F): the coldest temperatures in Earth’s atmosphere

37. Characteristics of the Atmosphere Thermosphere: –80 to 480km (50 to 298mi) –Temperatures began to rise –Main gases still nitrogen and oxygen, but the particles are very far apart Because of the small amount of molecular oxygen the thermosphere heats up as it absorbs intense solar radiation

42. Characteristics of the Atmosphere Exosphere: –480 km (298mi) –Some gases escape from the gravitational pull of Earth and exit into space –Also, some gases are captured by Earth’s gravitational field and added to Earth’s atmosphere

46. Characteristics of the Atmosphere Ionosphere: –When solar energy is absorbed in the lower thermosphere and upper mesosphere, electrically charged ions are formed This is the area of the atmosphere where these ions collect Electrons here reflect radio waves Without this layer radio waves would travel out into space

47. Characteristics of the Atmosphere Ionosphere: –Because the ions form as a result of solar radiation, there are fewer of them at night in the lower layers of the ionosphere –So, the radio waves can travel higher into the atmosphere before being reflected. –As, a result the radio waves return to Earth’s surface farther from their source than they do in the daytime

52. Characteristics of the Atmosphere Auroras take place in the ionosphere –Colorful light displays Encircling Earth’s magnetic poles Form when ions from the sun hit atoms and molecules causing photons to be emitted

55. Characteristics of the Atmosphere Changes in Earth’s atmosphere: –When Earth began to solidify about 4.4 billion years ago, volcanic eruptions released a variety of gases Hydrogen: H 2 Water vapor: H 2 O Ammonia: NH 3 Methane: CH 4 Carbon monoxide: CO Carbon dioxide: CO 2 Nitrogen: N 2 BUT NO OXYGEN: O 2

58. Characteristics of the Atmosphere The evolution of plants contributed oxygen to the atmosphere –Needed carbon dioxide and water, and sunlight All of which was plentiful –Photosynthetic organisms first evolved in the oceans since the land masses had high levels of UV light –Oxygen levels gradually increased and the ozone layer formed

60. Characteristics of the Atmosphere Once ozone layer formed life could evolve on the land: –Land plants evolved: oxygen production –Animals evolved: carbon dioxide production –These gases are recycled

62. Characteristics of the Atmosphere Greenhouse Effect: –Energy released by the Sun as radiation is absorbed by Earth’s surface –Some of this energy is released back toward space as radiation –Carbon dioxide, water vapor, nitrous oxide, and methane gases absorb some of this energy, so the atmosphere become warmer

69. Characteristics of the Atmosphere Too much carbon dioxide may cause global warming –Higher temperatures –Greater storms –Rising seas Must reduce carbon dioxide emissions

74. Water and Wind Water is continuously being moved through the troposhpere by the water cycle

78. Water and Wind Clouds form as warm, moist air rises –Water condenses into tiny droplets of liquid –Happens only in the troposphere

79. Water and Wind Cloud names describe their shape and the altitude at which they form –Clouds are named using combinations of the root words cirrus, stratus, and cumulus –Cirrus: thin and wispy Occur at high altitudes (between 3.7 and 6.8 mi) –Stratus: layered and look like sheets Form at lower altitudes (less than 3.8 mi) –Cumulus: white and fluffy with somewhat flat bottoms Form anywhere from about 500m to about 12km (7.5) Flat base is the place where rising air reaches the dew point (the temperature at which the rate of condensation equals the rate of evaporation for water vapor in the atmosphere

81. Water and Wind Dew point: 1.the atmospheric temperature (varying according to pressure and humidity) below which water droplets begin to condense and dew can form.

83. Water and Wind Cloud names reflect combined combinations characteristics: –Cirrostratus: high, layered clouds that form a thin, white veil over the sky –Altostratus and altocumulus: are simply stratus and cumulus clouds that occur at middle altitude

85. Water and Wind When a cloud name includes the root nimbo or nimbus, the cloud is a type that produces precipitation –Cumulonimbus: clouds are towering rain clouds that often produce thunderstorms –Nimbostratus: clouds are large, gray clouds that often produce steady precipitation

88. Water and Wind It's pretty well-known that most clouds are white, while rain clouds are usually a darker shade of gray. But why are rain clouds so dark? Let's start by discussing how clouds form. The air around you is full of water in its gaseous form, called water vapor. When the air near the ground warms, it starts to rise, taking the water vapor along with it. The air starts to cool as it rises higher into the sky, causing the water vapor to condense onto atmospheric dust from volcanoes, car exhaust and other sources. The resulting water droplets and ice crystals coalesce, or join together, to form clouds.

89. Water and Wind Unlike atmospheric particles that scatter more blue light than other colors (making the sky blue), the tiny cloud particles equally scatter all colors of light, which together make up white light.cloud However, rain clouds are gray instead of white because of their thickness, or height. That is, a cloud gets thicker and denser as it gathers more water droplets and ice crystals — the thicker it gets, the more light it scatters, resulting in less light penetrating all the way through it. The particles on the underside of the rain cloud don't have a lot of light to scatter to your eyes, so the base appears gray as you look on from the ground below. This effect becomes more pronounced the larger the water droplets get — such as right before they're large enough to fall from the sky as rain or snow — because they become more efficient at absorbing light, rather than scattering it.

91. Water and Wind Air Pressure: –Barometers are instruments used to measure air pressure –Changes in barometric pressure often accompany changes in weather –Barometric pressure, also called atmospheric pressure or air pressure, is the pressure that results from the weight of a column of air extending from the top of the thermosphere to the point of measurement

92. Water and Wind An air mass is a large (usually thousands of miles across) volume of air that has horizontally uniform properties in terms of temperature, and to a lesser extent humidity. Falling pressure may mean that a large air mass is leaving the area Rising pressure can mean that an air mass is moving in

94. Water and Wind Mercury barometers indicate air pressure by a column of mercury –At sea level: barometric pressure of air at 0 0 C is about 760mm of Hg This amount of pressure is defined as1atmosphere (1 atm) of pressure –SI unit: is the Pascal (Pa) »One Pa is equal to 1 Newton per square meter

97. Water and Wind Aneroid barometers indicate the pressure based on the volume of a sealed chamber of airmore portable but not as accurate as mercury thermometer

99. Water and Wind Wind: difference in pressure creates winds –If an airplane window were to break, the dense air in the plane’s cabin would spread out into the less dense air outside the cabin. The flow of air produced in this situation would push loose objects out the window –Differences in pressure in the atmosphere from one place to another is called a pressure gradient The air in a pressure gradient moves from areas of high pressure to areas of low pressure The movement of air from a high-pressure area to a low- pressure area is called wind

104. Water and Wind Coriolis Effect: Earth’s rotation affects the direction of the wind –Different latitudes on Earth move at different speeds as Earth rotates Equator rotates faster (larger circle) than higher latitudes (smaller circle) –Each goes through one full rotation in 24 hours –Equator rotation speed is 1,610 km/h (1,000 mi/h) to the east

105. Water and Wind Coriolis Effect: –The Coriolis effect is caused by the rotation of the Earth and the inertia of the mass experiencing the effect. Because the Earth completes only one rotation per day, the Coriolis force is quite small, and its effects generally become noticeable only for motions occurring over large distances and long periods of time, such as large-scale movement of air in the atmosphere or water in the ocean. Such motions are constrained by the surface of the earth, so only the horizontal component of the Coriolis force is generally important. This force causes moving objects on the surface of the Earth to be deflected in a clockwise sense (with respect to the direction of travel) in the Northern Hemisphere and in a counter-clockwise sense in the Southern Hemisphere. Rather than flowing directly from areas of high pressure to low pressure, as they would in a non-rotating system, winds and currents tend to flow to the right of this direction north of the equator and to the left of this direction south of it. This effect is responsible for the rotation of large cyclones.

111. Water and Wind When winds move North in the Northern Hemisphere, they curve to the right When winds move South in the Southern Hemisphere, they curve to the left

112. Water and Wind Wind moving South from the North Pole lags behind the rotation of Earth and travels West (to the left) –Wind has a slower speed than the spinning Earth Wind moving North from the South Pole travels West (to the left) because of its slower speed –Wind has a slower speed than the spinning Earth

113. Water and Wind Coriolis Effect is greatest near the equator, and decreases towards the poles.

118. Weather and Climate Front: is the place where a cold air mass and a warm air mass meet –A cold front is shown as a blue line with blue triangles –A warm front is shown as a red line with red semicircles Clouds, rain, and sometimes snow can occur at fronts When fronts move through an area, the result is usually precipitation and a change in wind direction and temperature

127. Weather and Climate Lightning is a discharge of electrical energy –Lightning is a massive electrostatic discharge between the electrically charged regions within clouds or between a cloud and the surface of a planet.

132. Weather and Climate Lightning instantly heats the air around it so much that the air expands faster than the speed of sound. –The shock wave created is thunder

133. Weather and Climate Tornadoes: –Air inside the funnel has very low pressure –As the funnel reaches the ground, higher- pressured air rushes into the low-pressured area The result is high-speed winds

136. Weather and Climate Hurricanes: large, rotating tropical storm systems –Occur over warm oceans –Named: Hurricanes in North America and the Caribbean Cyclones in the Indian Ocean Typhoons in the western Pacific –Intense low pressure –The rising air currents create fierce winds

141. Weather and Climate Temperatures tend to be higher at the equator

142. Weather and Climate Earth’s tilt and rotation account for our seasons

145. Weather and Climate Earth’s surface features affect climate