Atmospheric Dynamics & Processes (HL) (DP IB Environmental Systems & Societies (ESS)): Revision Note

Atmospheric dynamics & processes

• The atmosphere is a dynamic system that surrounds the Earth

• It is composed of various components and layers, each with distinct characteristics

  • These result from continuous physical and chemical processes occurring over time

Physical processes

Global warming

• The enhanced greenhouse effect is the main cause of global warming

• The enhanced greenhouse effect is different from the natural greenhouse effect

  • Human activities primarily drive the effect through releasing excessive amounts of greenhouse gases into the atmosphere

  • This leads to an intensified trapping of heat

• The natural greenhouse effect is a necessary process that helps regulate the Earth's temperature by trapping some heat to maintain a habitable climate

• In contrast, the enhanced greenhouse effect disrupts this balance

  • This occurs because greenhouse gas concentrations have been artificially increased beyond natural levels

Air movements

• Differences in the atmosphere's temperature and pressure have an impact on air movements

  • Warm air is less dense and rises, while cold air is denser and sinks

  • This creates convection currents that drive wind patterns and weather systems

    • E.g. the tricellular model of atmospheric circulation

Chemical processes

Ozone production

• Ozone is a molecule composed of three oxygen atoms (O₃)

  • It is mainly formed in the Earth's stratosphere through chemical reactions involving sunlight and oxygen

• Ozone plays a crucial role in protecting life on Earth by absorbing a significant portion of the Sun's harmful ultraviolet (UV) radiation

• When UV radiation from the Sun interacts with ozone molecules, some of the ozone absorbs the energy and breaks apart

  • This forms an oxygen molecule (O₂) and a free oxygen atom (O)

• The free oxygen atom can then combine with another oxygen molecule to form ozone again

• This ozone destruction and reformation create a dynamic equilibrium in the stratosphere

  • This is a continuous cycle of ozone molecules being broken apart and reformed

  • This dynamic equilibrium ensures that the concentration of ozone in the stratosphere remains relatively stable over time