TAG: GS 3: ECOLOGY AND ENVIRONMENT
THE CONTEXT: The Southern Ocean is known for having the cleanest air on Earth, and recent research has shed light on the factors contributing to this phenomenon.
EXPLANATION:
- Beyond the absence of human industrial activity, natural processes such as clouds, rain, and specific cloud patterns play crucial roles in maintaining low aerosol levels, thereby ensuring pristine air quality.
Role of Aerosols, Clean Air, Clouds and Rain
- Aerosols, comprising fine solid particles or liquid droplets suspended in the air, are a key determinant of air quality.
- In the atmosphere, these particles are mainly situated in the low layers of the atmosphere (< 1.5 km) since aerosol sources are located on the terrestrial surface.
- However, certain aerosols can still be found in the stratosphere, especially volcanic aerosols ejected into the high-altitude layers.
- Source of aerosols
- Natural sources – sea salt generated from breaking waves, mineral dust blown from the surface by wind, and volcanoes.
- Anthropogenic aerosols – sulphate, nitrate, and carbonaceous aerosols, and are mainly from fossil fuel combustion sources.
- Clean air is characterized by low levels of aerosols, irrespective of their source—whether natural or industrial.
- Clouds and rain play significant roles in regulating aerosol levels over the Southern Ocean by influencing the formation, growth, and removal of aerosol particles.
- Aerosol particles can serve as cloud condensation nuclei (CCN), which are necessary for cloud droplet formation.
- The number, size, and composition of aerosol particles are crucial for determining the number of droplets in clouds, which in turn affects cloud albedo, precipitation, and radiative forcing.
- Cloud formation and rainfall effectively “scrub” aerosol particles from the atmosphere, contributing to the region’s clean air.
Challenges in Research
- One of the primary challenges in understanding the relationship between clouds, rain, and aerosols has been the lack of high-quality observations in the Southern Ocean.
- However, advancements in satellite technology have enabled researchers to study cloud patterns with unprecedented detail, leading to new insights into atmospheric processes.
Identification of Honeycomb Cloud Patterns
- Researchers developed a computer program to identify distinct cloud patterns over the Southern Ocean, particularly focusing on honeycomb-shaped cloud formations.
- These patterns, characterized by open and closed cells, play a crucial role in regulating climate by reflecting or allowing sunlight, respectively.
- Open honeycomb cells, indicative of less cloudy weather, are associated with more intense rain showers that effectively wash aerosol particles from the air.
- Surprisingly, these cells produce more rain than closed cells, contributing significantly to the cleanliness of the air.
Seasonal Variations and Weather Systems
- The prevalence of open honeycomb clouds, and thus effective rain showers, is higher during the winter months when the air over the Southern Ocean is at its cleanest.
- Large-scale weather systems, such as storms, influence the formation of these cloud patterns.
Implications and Future Research
- Understanding the role of clouds, rain, and specific cloud patterns in maintaining clean air over the Southern Ocean has implications beyond atmospheric science.
- It contributes to improving climate models and enhancing predictions related to aerosol distribution and air quality.
Sothern Ocean:
- The Southern Ocean (also known as the Antarctic Ocean) is one of the five great ocean basins on Earth.
- It was formed around 34 million years ago when Antarctica and South America drifted apart, creating the Drake Passage.
- The passage is located between the Antarctica Peninsula’s tip and South America.
- It is made up of the portions of the world ocean south of the Pacific, Atlantic, and Indian oceans and their tributary seas surrounding Antarctica below 60° S.
- It is known for its strong winds, intense storms, dramatic seasonal changes and cold temperatures.
- It is dominated by the Antarctic Circumpolar Current (ACC): the longest, strongest, deepest-reaching current on earth.