Scientists have detected an unusually strong concentration of ozone in the lower stratosphere over the North Bay of Bengal, offering fresh insights into how ozone-rich air is transported and redistributed across the Indian region during winter.
The discovery was made through a coordinated nationwide atmospheric observation campaign involving research institutions across India, with the Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous institute under the Department of Science and Technology (DST), playing an important role.
The findings, published in Earth and Space Science by the American Geophysical Union (AGU), provide quantitative experimental evidence of the redistribution of stratospheric ozone over the Indian subtropical region.
Unusual Ozone Layer Found at 21–23 km Altitude
Ozone is concentrated mainly in the stratosphere, where it forms a protective layer that absorbs much of the Sun’s harmful ultraviolet radiation. Under normal conditions, peak ozone concentrations are generally found at altitudes of around 25–30 kilometres.
However, during the Phase-I NetRAD-ASMA campaign, scientists observed an unusually thick ozone-rich layer approximately 21–23 kilometres above the North Bay of Bengal. The ozone concentration in this layer was considerably higher than typically observed over eastern India.
The enhanced layer persisted for more than a day, prompting researchers to investigate the atmospheric processes responsible for its formation and persistence.
Nationwide Network Captured Atmospheric Changes
The study was conducted under the Phase-I NetRAD-ASMA campaign, designed to improve understanding of the complex dynamical processes governing Earth’s atmosphere. Scientists from multiple institutions participated in the programme, including Dr Manish Naja and Dr Samaresh Bhattacharjee from ARIES.
During the campaign, ARIES’ indigenously developed 206.5 MHz Stratosphere–Troposphere (ST) Radar at Nainital collected atmospheric observations alongside comparable radar systems located at Haringhata, Gadanki and Kochi.
Researchers also used instrument-equipped weather balloons to obtain detailed measurements of atmospheric temperature, winds and ozone concentrations at different heights. The simultaneous observations from multiple locations enabled scientists to track atmospheric circulation and compare vertical and horizontal movements of air across the country.
Satellite observations from NASA‘s Aura Microwave Limb Sounder (MLS) and INSAT-3DR were also incorporated into the analysis, along with simulations generated using advanced atmospheric models.
Transport, Not Sunlight, Behind Ozone Enhancement
The unusual ozone feature was detected during both daytime and nighttime. This indicated that sunlight-driven photochemical reactions were unlikely to be the main reason for the sudden enhancement.
Researchers subsequently examined several atmospheric processes, including convection, wind shear, horizontal transport and vertical air movement. Radar observations from ARIES revealed persistent downward motion of air in the lower stratosphere.
By combining evidence from balloons, radars, satellites and atmospheric models, scientists concluded that the enhanced ozone concentration was primarily linked to the transport of ozone-rich air into the region. This was followed by downward movement of the air mass and its subsequent compression, which contributed to the observed increase in ozone concentration.
Importance for Understanding Atmospheric Circulation
The study demonstrates how coordinated observations from different atmospheric research facilities can reveal complex processes that cannot be adequately captured through a single measurement system.
The findings are particularly significant for improving understanding of stratospheric circulation over the Indian subtropics, where interactions between large-scale atmospheric movements and regional dynamics can influence the distribution of ozone.
The contribution of ARIES’ ST Radar and balloon-based observations also highlights the growing capabilities of India’s indigenous atmospheric research infrastructure.
By combining ground-based instruments, satellite observations and numerical modelling, the NetRAD-ASMA campaign has provided scientists with a more comprehensive picture of how ozone-rich air masses move through the stratosphere. Such observations can strengthen future studies of atmospheric circulation, ozone variability and the processes governing the composition of Earth’s upper atmosphere.
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Author: Shivam
Shivam Dwivedi is a senior journalist with extensive experience in research-driven journalism, policy communication, and multi-platform storytelling. His areas of interest include international relations, defence, science & technology, education, urban development, agriculture, spirituality, and environmental sustainability. His work focuses on in-depth analysis, public discourse, and impactful narratives across governance and development sectors, with a strong commitment to the Sustainable Development Goals (SDGs). Contact: [email protected]
