ATMOSPHERE
Atmosphere Basics
•Combination of gases, dust, water droplets, and ice crystals •Surrounds the Earth •Extends from the Earth’s surface to outer space Permanent Atmospheric Gases •Earth’s atmosphere consists mainly of nitrogen (78 percent) and oxygen (21 percent). •The amounts of nitrogen and oxygen in the atmosphere are fairly constant over recent time. Variable Atmospheric Gases •The concentrations of some atmospheric gases are not as constant over time. •The amount of water vapor, ozone, and carbon dioxide vary significantly from place to place. Water Vapor (H2O(g)) •Invisible, gaseous form of water •Can range of 0% - 4% •Concentration depends on the seasons, altitude, and properties of the surface underneath Carbon Dioxide (CO2) •During the past 150 years, the concentration of atmospheric carbon dioxide has increased, due primarily to the burning of fossil fuels. •Currently 0.039% (up by 0.028%) Ozone (O3) •Mostly in ozone layer (20 – 50 km above) •Only 0.0012% but plays important role in blocking out harmful rays from the sun •Concentration has decreased due to CFCs which are now banned •Scientists estimate it should fully recover by the 2100 Atmosphere Particles •Contains variable amounts of solids in the form of tiny particles, such as dust, salt, and ice •Fungi and bacteria are often attached to these particles Review of Thermal Energy and Heat •Remember – all matter is made of particles in constant, random motion! •These moving particles contain kinetic energy. •The total kinetic energy of the moving particles is called thermal energy. •Heat is the transfer of thermal energy from regions of higher temperature to regions of lower temperature Energy Transfer in the Atmosphere In the atmosphere thermal energy is transferred by: –Radiation –Conduction –Convection Radiation •Transfer of thermal energy by electromagnetic waves •Thermal energy is transferred from the Sun to Earth by radiation Absorption and Reflection •Incoming solar radiation is either reflected back into space or absorbed by Earth’s atmosphere or its surface. •30% is reflected •20% is absorbed by atmosphere and clouds •50% is absorbed by Earth’s surface Rate of Absorption •Depends on physical characteristics of the surface and the amount of solar radiation •Examples – water heats and cools more slowly; dark colors absorb energy faster Conduction •Transfer of thermal energy when objects at two different temperatures are in contact •Occurs between the Earth’s surface and lowest part of the atmosphere Convection •Remember – convection is the transfer of thermal energy by the movement of heated material from one place to another •Near the Earth’s surface air becomes heated, expands, and rises then as it rises it cools, contracts, and sinks. •This creates convection currents in the atmosphere. |
Troposphere
•Closest to the Earth’s surface •Contains most of the atmosphere’s mass •Weather occurs in this layer •Air temperature decreases with altitude •Top is called tropopause Stratosphere •Above tropopause •Contains the ozone layer •Air temperature increases with altitude since the ozone layer absorbs the sun’s energy •Ends at the stratopause Mesosphere •Above the stratopause •Air temperature decreases with altitude since very little solar radiation is absorbed •Ends at mesopause where you find shooting stars Thermosphere •Low air density so temperature rises (can be over 1000°C) •Contains the ionosphere (made up of charged particles) •Ends at thermopause Exosphere •Outermost layer •Transitional region between the Earth’s atmosphere and outer space |
State of the Atmosphere
Temperature
Temperature is different from heat
-Temperature measures the average speed of the particles of a substance
-Heat describes a transfer of energy
Temperature scales
-Fahrenheit
-Celsius
-Kelvin
Dew point (condensation temp.)
-This varies depending on water content of the air
-When temperature reaches dew point, condensation can occur
Vertical temperature changes
-Air cools as elevation increases
-Dry air cools at about 10ºC / 1000 m
-If you travel high enough, the air cools to the dew point. This is called the lifted condensation level (LCL)
-Moist air cools at about 6ºC / 1000 m
Pressure
Air pressure and density
-The air near the Earth’s surface is denser than air further up
-The higher you go, the lower the pressure because . . .
Temperature–Pressure relationship
-As the temperature goes up, the pressure goes up
-This relationship is called a direct relationship
Temperature-Density relationship
-As the temperature up, the density goes down
-This relationship is called an inverse relationship
Temperature Inversions
-The temperature of the air increases the higher the elevation.
-These layers act like a lid, holding in gases below
Wind
-Results from differences in temperature.
-Warm air has a lower density and rises causing low pressure
-Cooler air has a higher density and falls, causing high pressure
Relative Humidity
Relative humidity depends on:
-How much moisture is in the air
-How much moisture could be in the air
-Note – warm air holds more moisture
Temperature is different from heat
-Temperature measures the average speed of the particles of a substance
-Heat describes a transfer of energy
Temperature scales
-Fahrenheit
-Celsius
-Kelvin
Dew point (condensation temp.)
-This varies depending on water content of the air
-When temperature reaches dew point, condensation can occur
Vertical temperature changes
-Air cools as elevation increases
-Dry air cools at about 10ºC / 1000 m
-If you travel high enough, the air cools to the dew point. This is called the lifted condensation level (LCL)
-Moist air cools at about 6ºC / 1000 m
Pressure
Air pressure and density
-The air near the Earth’s surface is denser than air further up
-The higher you go, the lower the pressure because . . .
Temperature–Pressure relationship
-As the temperature goes up, the pressure goes up
-This relationship is called a direct relationship
Temperature-Density relationship
-As the temperature up, the density goes down
-This relationship is called an inverse relationship
Temperature Inversions
-The temperature of the air increases the higher the elevation.
-These layers act like a lid, holding in gases below
Wind
-Results from differences in temperature.
-Warm air has a lower density and rises causing low pressure
-Cooler air has a higher density and falls, causing high pressure
Relative Humidity
Relative humidity depends on:
-How much moisture is in the air
-How much moisture could be in the air
-Note – warm air holds more moisture
Moisture in the Atmosphere
Cloud Formation
-Warm, moist air rises.
-This air expands and cools
-The air reaches its dew point
-Water droplets condense around condensation nuclei
-A cloud forms
Causes for warm air to rise
-Orographic lifting
-Warm air encounters cold air
Atmospheric stability
-A stable atmosphere has no clouds, or thin, layers of clouds.
-An unstable atmosphere will have vertical development. Thunderstorms indicate an unstable atmosphere.
Latent heat
-Energy required to evaporate water is stored in the water vapor.
-When the water vapor condenses this heat is released.
Types of clouds
-Cirrus
-Cumulus
-Stratus
-Cirrostratus
-Cirrocumulus
-Altostratus
-Altocumulus
-Nimbostatus
-Stratocumulus
-Cumulonimbus
-Warm, moist air rises.
-This air expands and cools
-The air reaches its dew point
-Water droplets condense around condensation nuclei
-A cloud forms
Causes for warm air to rise
-Orographic lifting
-Warm air encounters cold air
Atmospheric stability
-A stable atmosphere has no clouds, or thin, layers of clouds.
-An unstable atmosphere will have vertical development. Thunderstorms indicate an unstable atmosphere.
Latent heat
-Energy required to evaporate water is stored in the water vapor.
-When the water vapor condenses this heat is released.
Types of clouds
-Cirrus
-Cumulus
-Stratus
-Cirrostratus
-Cirrocumulus
-Altostratus
-Altocumulus
-Nimbostatus
-Stratocumulus
-Cumulonimbus