Articles written in Journal of Earth System Science

    • Ozone chemistry and dynamics at a tropical coastal site impacted by the COVID-19 lockdown


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      The nationwide lockdown in India to curb the spread of Coronavirus disease 2019 (COVID-19) led to colossal reduction in anthropogenic emissions. Here, we investigated the impact of lockdown on surface ozone (O$_{3}$) and nitrogen dioxide (NO$_{2}$) over a tropical coastal station – Thumba, Thiruvananthapuram (8.5$^{\circ}$N, 76.9$^{\circ}$E). Daytime as well as night-time NO$_{2}$ showed reduction by 0.8 (40%) and 2.3 (35%) ppbv, respectively during the lockdown period of 25–30 March 2020 as compared with the same period of previous 3 years. Unlike many urban locations, daytime surface O$_{3}$ is found to be dramatically reduced by 15 ppbv (36%) with O$_{3}$ production rate being lower by a factor of 3 during the lockdown. Interestingly, a feature of O$_{3}$-hump during the onset of land breeze typically observed during 1997–1998 has reappeared with magnitude of 5–10 ppbv. A photochemical box model, capturing this feature, revealed that significant O$_{3}$ sustained till onset of land breeze over the land due to weaker titration with NO$_{x}$ during lockdown. It is suggested that the transport of this O$_{3}$ rich air with onset of land breeze led to the observed hump. Our measurements unravel a remarkable impact of the COVID-19 lockdown on the chemistry and dynamics of O3 over this tropical coastal environment.

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