Role of SHM in redistribution of energy within Earth's atmosphere and oceans

  • Use a video micro-lecture that describes how oscillations with the Brunt-Väisälä frequency in the atmosphere and oceans cause many natural phenomena that can influence Earth's climate.
  • Conclude with a discussion on how such a redistribution of energy within Earth's atmosphere and oceans, can impact its climate.

Use the video micro-lecture, 'What causes stripey clouds?' to explain how SHM in the atmosphere cause cloud patterns, cloud formations and results in thunderstorms. The air close to the earth's surface is denser than the air higher above - the reason why it is harder to breathe in the mountains. When parcels of air are displaced from their original position (maybe due to the presence of an obstacle like a mountain), they oscillate up and down. When they move upward, they become cooler and when they move downward, they heat up. If an upward moving air parcel contains water vapour, this water vapour condenses and forms clouds. The downward moving air heats up and does not form clouds. This forms a wave-like pattern of clouds that are visible quite often in the sky.

  • The video describes the Brunt-Väisälä frequency in SHM. The oscillation of air/water parcels depends on the rate of change of density with height and acceleration due to gravity. If the density decreases with height, the force always points to the position of rest and parcels exhibit SHM. If the density decreases rapidly, the oscillation is faster (can you explain why?) and vice versa.
  • This frequency of oscillation is called the Brunt-Väisälä Frequency. In such a situation, the atmosphere is said to be stable. If the density increases with height, then the parcel always experiences a force upward. In this case, no SHM is possible and the atmosphere is unstable. In such a situation cloud formation and thunderstorms occur.

Sir David Brunt (1886-1965)

  • The video also descibes similar occurrences of SHM in the oceans where energy is obtained from the coasts, at the surface and from the ocean floor. Since the ocean is stratified, some of this energy is converted to SHM of water parcels. The energy contained in these movements results in the generation of internal waves that transport this energy to other parts of the ocean. These internal waves also transport plankton larvae from the deep ocean to the coasts.
  • Ponder on how such a redistribution of energy within Earth's atmosphere and oceans, can impact its climate.

Vilho Väisälä (1889-1969)


Video by Professor Mike Merrifield, University of Nottingham