6.1 Introduction to the atmosphere

Changes

The atmsphere is dynamic and has undergone many changes over time.

Inputs

• Water (evaporation and transpiration)

• CO2, SO4 and NO2 from combustion

• NH4 from livestock

• Volcanic ash

• Solar radiation

• oxygen through photosynthesis

• CO2 from respiration

• aerosols

Outputs

• precipitation

• solar radiation

• oxygen for respiration

• CO2 for photosynthesis

Components of the athmosphere

• Nitrogen - 78% - Dilutes oxygen and prevents rapid burning at the earth's surface. Living things need it to make proteins. Nitrogen cannot be used directly from the air. The Nitrogen Cycle is nature's way of supplying the needed nitrogen for living things. 

• Oxygen - 21% - Used by all living things. Essential for respiration. It is necessary for combustion or burning. 

• Argon - 0.9% - Used in light bulbs. 

• Carbon Dioxide - 0.03% - Plants use it to make oxygen. Acts as a blanket and prevents the escape of heat into outer space. Scientists are afraid that the burning of fossil fuels such as coal and oil are adding more carbon dioxide to the atmosphere. 

• Water Vapor - 0.0 to 4.0% - Essential for life processes. Also prevents heat loss from the earth. 

• Trace gases - gases found only in very small amounts. They include neon, helium, krypton, and xenon.

Trophosphere

• Temperature declines by around 6.5°C per kilometer increase in altitude

• Wind speeds increase with altitude. The jet stream occurs at the top of the troposphere.

• Most of the atmospheric mass is found.

• Most of our weather occurs here.

• Humans and other organisms have most interaction e.g. through exchange of gases or through introduction of pollutants.

• Greenhouse gases (GHG) help to regulate the temperature of the earth.

Strathosphere

• Temperature is constant at about -60°C in the lower part of the stratosphere, which is shielded by the ozone layer but then increases with altitude.

• The air is dry.

• Winds increase with height.

• Ozone layer at the top of the stratosphere. Stratospheric ozone absorbs ultra violet radiation from the sun

Albedo

a measure of the reflectivity of a surface.

Albedo effect

a measure of how much of the Sun's energy is reflected back into space. More water vapour in the atmosphere means more cloud formation. More clouds lead to increased albedo of the earth.

Greenhouse Gases

They trap in heat and make the Earth warmer. If there is too much greenhouse gases, it would trap too much heat causing global warming.

• Maintain mean global temperature

• Normal and necessary condition for life on Earth

• allow short wavelengths of radiation such as visible light and UV too pass through to the Earth's surface, but they trap the longer wavelengths such as infrared radiation