Atmosphere Chapter 11 PDF

Atmosphere CHAPTER 11  Gases in the Atmosphere ► Air is a combination of gases, and particles such as dust, water droplets, and ice crystals ► Some gases are permanently in the atmosphere. ► About 99% of the atmosphere is composed of Nitrogen (N) and Oxygen ► Remaining 1% c...

Atmosphere CHAPTER 11  Gases in the Atmosphere ► Air is a combination of gases, and particles such as dust, water droplets, and ice crystals ► Some gases are permanently in the atmosphere. ► About 99% of the atmosphere is composed of Nitrogen (N) and Oxygen ► Remaining 1% consists of Argon (Ar), Carbon Dioxide (CO2), and Water Vapor and other trace gases ► Some gases are not as constant over time such as Water Vapor (H2O) and Ozone (O3) which can vary significantly from place to place ► Water Vapor and CO2 help regulate the amount of energy the atmosphere absorbs and emits back to the Earth’s surface  Gases in the Atmosphere ► Atmosphere- layer of gases that surrounds Earth ► Water Vapor – invisible gaseous form of water ► Carbon Dioxide in the Atmosphere has increased over time due to the burning of Fossil Fuels ► The Ozone layer blocks harmful ultraviolet rays from reaching Earth’s surface. Due to a chemical called chlorofluorocarbons which react and break down the ozone, this layer is being destroyed. ► The atmosphere keeps Earth livable as it protects from ultraviolet rays, it keeps Earth warm during the day and cool as night while supplying air for us to breathe  Atmospheric Layers ► Classified into 5 different layers ► 1. Troposphere – layer closest to Earth’s surface, ends at tropopause where temps stop decreasing and can be as low as -76F or - 60C, contains most of the mass of the atmosphere, Weather occurs here, Temps decrease as altitude increases ► 2. Stratosphere – Above the tropopause, contains the ozone layer , ends at stratopause, temperatures increase as altitude increases, below the ozone layer temps stay constant but starting at the bottom of t he ozone, temps start increasing. The heating is caused by ozone molecules which absorb ultraviolet rays from the Sun. About 99.9% of the mass of Earth’s atmosphere is below the stratopause  Atmospheric Layers ► 3. Mesosphere – above the stratosphere, ends at mesopause where temps stop decreasing, air temperatures decrease with altitude, This temperature decrease occurs because very little solar radiation is absorbed in this layer ► 4. Thermosphere – above the mesosphere, absorbs solar radiation, area of extremely low density of air which causes temps to rise and become as high as 2000C or 3632F, contains the ionosphere which is made of electrically charged particles ► 5. Exosphere – outermost layer, transition between the atmosphere and space, no clear boundary at top, number of atoms and molecules becomes smaller as altitude increases, atoms and molecules rarely collide and can escape into outer space  Energy Transfer ► All materials are made of particles such as atoms and molecules which are always moving in all directions with various speeds or in Random Motion ► Kinetic Energy – energy produced by an object in motion ► Thermal Energy – total energy of the particles in an object due to their random motion ► Heat is the transfer of thermal energy from a region of higher temperature to a region of lower temperature ► In the atmosphere, thermal energy can be transferred by radiation, conduction, and convection ► Radiation – the transfer of thermal energy by electromagnetic waves  Energy Transfer ► Like a heat lamp for food, the Sun gives off energy that is absorbed by the Earth and reflected by Earth’s atmosphere and Earth’s surface ► Most of the solar energy that reaches Earth is in the form of visible light waves and infrared waves ► Almost all of the visible light passes through the atmosphere and hits and is absorbed by Earth’s surface ► After absorption, the surface emits infrared waves which are somewhat absorbed by the atmosphere ► About 30% of solar radiation is reflected into space by Earths surface, clouds, or atmosphere. Another 20% is absorbed by the atmosphere and clouds. About 50% is absorbed directly or indirectly by Earth’s surface and keeps it warm  Energy Transfer ► The rate of absorption varies depending on physical characteristics of the area and the amount of solar radiation it receives ► For example, water heats and cools slower than land and Darker objects absorb energy faster ► Conduction – transfer of thermal energy between objects when their atoms or molecules collide ► Can occur more easily in solids or liquids, where particles are closer together than in gases ► Because air is made of mostly gases, it is a poor conductor of thermal energy ► On Earth, conduction occurs between the Earth’s surface and the lowest point of the atmosphere  Energy Transfer ► Convection – transfer of thermal energy by the movement of heated material from one place to another ► Parcels of air near Earth’s surface are heated, become less dense than the surrounding air and rise ► As the warm air rises, it cools and the density increases ► When the air becomes cooler than the surrounding air, it becomes more dense and it sinks ► As it sinks, it warms again and the process repeats ► Convection currents are the main driving force of energy transfer in the atmosphere  Properties of the Atmosphere ► Temperature – the measure of the average kinetic energy of the particles in a material ► The higher the temperature, the faster particles are moving ► We typically measure temperature using one of two common scales; Fahrenheit, or Celsius ► The temperature scale used in science is Kelvin (K) ► Fahrenheit and Celsius are based on freezing and boiling point of water; Kelvin scale is absolute zero, the lowest temp any substance can get ► We measure temperature with a thermometer  Air Pressure ► If you hold your hand out in front of you, Earth’s atmosphere exerts a downward force on it due to the weight of the atmosphere above it ► The force exerted on your hand divided by its area is the pressure exerted on your hand ► Air pressure – pressure that is exerted on a surface by the weight of the atmosphere above the surface ► Air pressure is measured in Newtons and millibars ► As you increase altitude, Air pressure decreases because the amount of atmosphere above you decreases as you are rising above it  Temperature Inversion ► Temperature inversion – increase in temp with height in an atmospheric layer ► Remember in the troposphere, the high you go the colder it gets as temps decrease; in a temp inversion, colder air remains on bottom while temps rise as you increase altitude ► This can happen in the troposphere when you have rapid cooling on a cold, clear winter night when the air is calm. Under these conditions, the land does not radiate thermal energy to the lower parts of the atmosphere therefore the lower parts of the atmosphere become cooler than the parts above them, so the temps increase with height ► Can lead to fog or low level clouds or smog; can worsen air pollution problems because the polluted air becomes trapped under the warmer air and are unable to be lifted from Earth’s surface  Instruments ► Thermometer – measures temperature ► Barometer – measures Air pressure ► Hygrometer – measures the humidity and water vapor in the air ► Rain Gage – measures the amount of rain that has fallen ► Anemometer – measures wind speed ► Weather vane – shows the direction of the wind  Cloud formation ► A cloud can form when a rising air mass cools ► The cooling of an heated airmass as it rises can cause water vapor in the air to condense ► Lifted condensation level – height at which condensation of water vapor occurs in an air mass ► When a rising air mass reaches the lifted condensation level, water vapor condenses (gas->liquid), around condensation nuclei ► Condensation nuclei is a small particle in the atmosphere around which water droplets can form ► The droplets that form can be liquid water or ice, depending on surrounding temps and when the number of these droplets is large enough, a cloud is visible  Atmospheric Stability ► The stability of air masses determines t he type of clouds that form and the associated weather patterns ► As an air mass rises, it cools and will continue to rise as long as it is warmer than the surrounding air ► Sometimes, an air mass that has began to rise sinks back to its original position ► When air resists rising, it is considered Stable and will form fair weather clouds ► Suppose that the temperature of the surrounding air cools faster than the temperature of the rising air mass ► In this case the air mass will always be less dense and will continue to rise and be considered unstable and create clouds associated with thunderstorms  Atmospheric Lifting ► Clouds can form when moist air rises, expands and cools ► Air rises when it is heated and becomes warmer than the surrounding air (convective lifting) ► Clouds can also form when air is forced upwards or lifted by mechanical processes ► Clouds can form when air is forced to rise over elevated land or other topographic barriers like a mountain range – Orographic lifting ► Most of the rainiest places on Earth are located on the windward sides of a mountain slope  Atmospheric Lifting ► Air can also be lifted by convergence ► Convergence – occurs when air masses move into the same area from different directions and leads to some of the air forced upwards ► This process is even more pronounced when air masses at different temperatures collide ► The warmer air is forced over the cooler more dense air. The warmer air cools as it rises ► If the rising air cools to the dew point temperature, then water vapor can condense on condensation nuclei and form a cloud  Types of Clouds ► Clouds can have different shapes, some puffy, some thin and feather-like ► Clouds can form at different altitudes (low below 2000m, middle 2000- 6000m, high >6000m) clouds that form right at Earth’s surface is called Fog ► When a warm air mass rises, it will stop when the temps of the surrounding are equal to the air mass ► If a cloud has formed, it will flatten out and winds will spread it horizontally into stratocumulus or layered cumulus clouds ► Cumulus – clouds that are puffy, lumpy-looking clouds that usually occur below 2000m (low) ► Stratus – layered sheetlike clouds that can cover much or all of the sky, often forms when fog lifts (Nimbostratus produces precipitation)  Types of Clouds ► Altocumulus (white or gray and form large round masses or wavy rows) and Altostratus (gray appearance and form in thin sheets ) are middle level clouds that made of ice crystals and water droplets due to the colder temperatures generally present at these altitudes ► Middle clouds are usually layered and produce mild precipitation ► High clouds are made of ice crystals as temps at this altitude are below freezing ► Cirrus – wispy indistinct appearance ► Cirrostratus – forms as a continuous layer and can be transparent or dense enough to block the Sun or Moon ► Cirrocumulus – rippled appearance  Types of Clouds ► If the air that makes up a cumulus cloud are unstable, the cloud will be warmer than the surrounding air and will continue to grow upward ► As it rises, water vapor condenses and the air continues to increase in temperature due to the release of latent heat ► It can keep rising through middle altitudes into a towering giant and is capable of producing heavy rains, strong winds, and hail characteristics of some thunderstorms ► This is a cumulonimbus