A better understanding of organic hydroperoxides
17 March 2023
Published online 9 March 2022
Long-range atmospheric circulation patterns explain how lockdown-related reductions in air pollution in India increased dust levels in the Middle East.
The subdued transportation and industrial activity resulting from lockdowns during the pandemic generally reduced global pollution, but also created atmospheric conditions that whipped up unusually high levels of dust across the Arabian Peninsula.
Diana Francis, of Khalifa University of Science and Technology in the United Arab Emirates, was first alerted to this surprising effect while looking at research performed in early 2020 into changes in global emissions and pollution . That data showed clear evidence of reduced carbon dioxide levels in the atmosphere and oceans, but also indicated that the impact of the lockdowns was not universally positive from an air quality perspective. “I looked at the satellite imagery and saw very active dust emissions, especially over Iraq, Kuwait and northeast Saudi Arabia,” she says.
This prompted Francis and colleagues to embark on a comparative analysis of meteorological activity, atmospheric conditions and airborne particle levels during the first three months of the pandemic relative to several years before the emergence of COVID-19. Their data confirmed the sharp increase in dust levels over the peninsula in early 2020 relative to the period from 2016 to 2019. But they also revealed an unexpected origin of this phenomenon: lockdown-induced changes in the atmospheric conditions over the Indian subcontinent.
Francis points out that the Arabian Peninsula is subject to air currents known as the Shamal winds, which arise from an air pressure gradient between these two regions. When India imposed its lockdown in late March 2020, the resulting fall in air pollution also affected the amount of solar energy absorbed by the Earth’s surface. “This resulted in a steeper pressure gradient, and therefore stronger and more frequent Shamal winds,” says Francis. These winds subsequently swept across the Saudi Arabian deserts, gathering large quantities of dust and scattering it across the peninsula.
These results highlight the remarkable long-range connectivity of global atmospheric patterns, and how perturbations in one region—including those arising from efforts such as emissions control—could have unexpected outcomes elsewhere. Francis and colleagues are now looking more deeply into the underlying forces that shape the Shamal winds, and how the dust levels generated by those air currents is changing over time. This is not just a matter of air quality, and Francis notes that these winds have far-reaching consequences. “It is known that Shamal winds help decrease the temperature of the water column in the Arabian Gulf, helping coral reefs survive extreme heat,” she says.
Francis, D. et al. Increased Shamal winds and dust activity over the Arabian Peninsula during the COVID-19 lockdown period in 2020. Aeolian Research 55,100786 (2022).