Definition
Dynamic atmospheric system
A dynamic atmospheric system is one in which gases, energy, and particles are continuously transformed and redistributed through interacting physical and chemical processes.
- The atmosphere is a dynamic, constantly changing system influenced by physical and chemical processes that operate from the Earth’s surface up into the upper layers.
- These processes shape atmospheric composition, temperature structure, circulation patterns, and the formation or destruction of key gases such as ozone.
- Because the atmosphere receives continuous inputs of solar radiation, aerosols, gases, and energy, it continually adjusts through feedback mechanisms and exchanges with other Earth systems.
Physical Processes in the Atmosphere
1. Global Warming
- Global warming is caused by an increase in greenhouse gas concentrations, which enhances the natural greenhouse effect.
- Human activities such as burning fossil fuels, deforestation, and industrial agriculture add excess carbon dioxide, methane, and nitrous oxide to the atmosphere.
- This increases radiative forcing, traps more heat, and alters atmospheric circulation, humidity levels, and climate patterns.
Global warming is a physical process because it involves changes to the flow and storage of heat energy in the atmosphere.
Common Mistake- Don't confuse the natural greenhouse effect with the enhanced greenhouse effect.
- The former is essential for life, while the latter is driven by human activities and causes global warming.
2. Air Movements: Temperature and Pressure Differences
- Warm air rises because it becomes less dense.
- Cold air sinks because it is more dense.
- This difference creates convection currents, the basis of global wind systems.
- These convection currents drive:
- the tricellular model of circulation (Hadley, Ferrel, Polar cells),
- prevailing winds such as trade winds and westerlies,
- and large-scale weather systems (cyclones, jet streams, monsoons).
- Air moves from high-pressure regions to low-pressure regions.
- These pressure differences are generated by temperature contrasts, such as:
- warm equatorial air rising and creating low pressure,
- cold polar air sinking and creating high pressure.
- The trade winds blow from east to west near the equator, while the westerlies blow from west to east in mid-latitudes.
- These winds are part of the tricellular model of atmospheric circulation, which redistributes heat globally.
Chemical Processes in the Atmosphere
Ozone Production
- The stratosphere contains molecular oxygen (O₂) which absorbs high-energy ultraviolet (UV) radiation from the Sun.
- This splits O₂ into two free oxygen atoms (O).
- A free oxygen atom then combines with another O₂ molecule to form ozone (O₃).
The Ozone-Oxygen Cycle (Dynamic Equilibrium)
- UV radiation splits O₂ into O + O.
- A free oxygen atom (O) collides with O₂ forming O₃.
- Another UV photon can break O₃ into O₂ + O.
- The oxygen atom can rejoin O₂ again.
- This creates a dynamic equilibrium, maintaining stable ozone levels in the stratosphere.
Stratospheric Ozone and UV Protection
- The ozone layer filters out over 90 percent of harmful UV-B radiation.
- In the 1970s–1990s, CFC emissions led to major ozone depletion over Antarctica.
- The Montreal Protocol (1987) phased out CFCs, demonstrating global cooperation in protecting atmospheric chemical processes.
