Atmospheric Notes
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 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 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 • Contains meteors 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 refion between the Earth’s atmosphere and outer space Review • 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: o Radiation o Conduction o Convection Radiation • Transfer of thermal energy by electromagnetic waves • Thermal energy is transferred from the Sun to Earth by radiation • Incoming solar radiation is either reflected back into space or absorbed by Earth’s atmosphere or its surface. o 30% reflected o 20% absorbed by atmosphere and clouds o 50% 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. |
More Notes
Temperature
X 100
Amount of moisture possible
Cloud formation
- 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 temperature)
- Temperature to which air must be cooled at constant pressure to reach saturation
- This varies depending on water content of the air
- When temperature reaches dew point, condensation can occur
- Temperature to which air must be cooled at constant pressure to reach saturation
- Vertical temperature change
- 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
- 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 ↑, the pressure goes ↑ .
- This relationship is called a direct relationship.
- Temperature- density relationship
- As the temperature ↑, the density goes _↓_ .
- This relationship is called an inverse relationship.
- The temperature of the air increases the higher the elevation.
- These layers act like a lid, holding in gases below.
- 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
- How much moisture is in the air
- How much moisture could be in the air
- Note – warm air holds more moisture.
- If the relative humidity is 100% this means the atmosphere is more saturated.
X 100
Amount of moisture possible
Cloud formation
- Step to making clouds
- Warm, moist air rises.
- This air expands and cools
- The air reaches its dew point
- Water droplets condense around condensation nuclei
- Surface on which water droplets can form. Smoke or dust particles can act as condensation nuclei
- A cloud forms
- Causes for warm air to rise
- Orographic lifting
- Cloud formation as a result of wind moving air into a mountain. This moves the air upward.
- Warm air encounters cold air
- Orographic lifting
- Atmospheric stability
- The ability to resist rising
- 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
- The heat exchanged during a phase change
- Energy required to evaporate water is stored in the water vapor.
- When the water vapor condenses this heat is released.
- Types of clouds
- Cirrus
- Form high in atmosphere, made of ice crystals, appear as thin, white, feathery clouds
- Cumulus
- Flat-based, puffy white clouds with cauliflower appearance on top. Extends vertically several thousand ft.
- Stratus
- Layered cloud that covers most of the sky. Forms at low altitudes. Often gray.