Shubhajyoti Roy

Tropospheric ozone pollution in South Asia is mainly blamed on anthropogenic emissions. However, based on ERA5 reanalysis data, this study highlights the contribution of stratospheric ozone intrusions into the Upper Troposphere and Lower Stratosphere (UTLS) associated with Sudden Stratospheric Warming (SSW) events in enhancing upper tropospheric ozone over the South Asian region. We report an enhancement in ozone in the UTLS by more than 80 % for 2018 and ∼ 30 % within ±6 d of the onset during SSW events concurrent with the westerly phase of Quasi-biennial oscillation (WQBO-SSW) compared to non-SSW years. The equatorward shift (south of 30° N) of the subtropical jet during WQBO-SSW causes lowering of the tropopause and more Rossby-wave breaking in the upper troposphere. This results in higher stratospheric ozone intrusions over the South Asian region. The ozone enhancement during WQBO-SSW events produces an instantaneous radiative forcing at the top of the atmosphere of 0.09±0.05 W m−2 due to UTLS ozone changes and 0.17±0.05 W m−2 from total-column ozone changes over South Asia.

Tropospheric ozone pollution in South Asia is mainly blamed on anthropogenic emissions. However, this study highlights the contribution of stratospheric ozone intrusions into the troposphere associated with sudden stratospheric warming (SSW) events in enhancing tropospheric ozone over the South Asian region using ERA-5 reanalysis data. We report that specifically split-downward propagating SSWs (dSSWs) cause enormous ozone enhancement in the upper troposphere and lower stratosphere (UTLS) over South Asia around the dSSW-onset, with a maximum of ~290 % within ±30 days. The ozone intrusions propagate deep into the troposphere, causing near-surface maximum ozone increase by 43 % within ±30 days around the SSW-onset. The ozone enhancement increases ozone radiative forcing in the troposphere by 0.04±0.03 W.m^-2 and UTLS by 0.08±0.06 W.m^-2 over South Asia. Frequent SSW events in a warming climate will thus likely increase stratospheric ozone intrusions and ozone radiative forcing over South Asia, potentially exacerbating regional climate warming. The elevated tropospheric ozone amounts due to stratospheric intrusions are posing threat to humans and vegetation.

Tropospheric ozone pollution in South Asia is mainly blamed on anthropogenic emissions. However, this study highlights the contribution of stratospheric ozone intrusions into the troposphere associated with sudden stratospheric warming (SSW) events in enhancing tropospheric ozone over the South Asian region using ERA-5 reanalysis data. We report that specifically split-downward propagating SSWs (dSSWs) cause enormous ozone enhancement in the upper troposphere and lower stratosphere (UTLS) over South Asia around the dSSW-onset, with a maximum of ~290 % within ±30 days. The ozone intrusions propagate deep into the troposphere, causing near-surface maximum ozone increase by 43 % within ±30 days around the SSW-onset. The ozone enhancement increases ozone radiative forcing in the troposphere by 0.04±0.03 W.m^-2 and UTLS by 0.08±0.06 W.m^-2 over South Asia. Frequent SSW events in a warming climate will thus likely increase stratospheric ozone intrusions and ozone radiative forcing over South Asia, potentially exacerbating regional climate warming. The elevated tropospheric ozone amounts due to stratospheric intrusions are posing threat to humans and vegetation.

Tropospheric ozone pollution in South Asia is mainly blamed on anthropogenic emissions. However, this study highlights the contribution of stratospheric ozone intrusions into the troposphere associated with sudden stratospheric warming (SSW) events in enhancing tropospheric ozone over the South Asian region using ERA-5 reanalysis data. We report that specifically split-downward propagating SSWs (dSSWs) cause enormous ozone enhancement in the upper troposphere and lower stratosphere (UTLS) over South Asia around the dSSW-onset, with a maximum of ~290 % within ±30 days. The ozone intrusions propagate deep into the troposphere, causing near-surface maximum ozone increase by 43 % within ±30 days around the SSW-onset. The ozone enhancement increases ozone radiative forcing in the troposphere by 0.04±0.03 W.m^-2 and UTLS by 0.08±0.06 W.m^-2 over South Asia. Frequent SSW events in a warming climate will thus likely increase stratospheric ozone intrusions and ozone radiative forcing over South Asia, potentially exacerbating regional climate warming. The elevated tropospheric ozone amounts due to stratospheric intrusions are posing threat to humans and vegetation.

Tropospheric ozone pollution in South Asia is mainly blamed on anthropogenic emissions. However, this study highlights the contribution of stratospheric ozone intrusions into the troposphere associated with sudden stratospheric warming (SSW) events in enhancing tropospheric ozone over the South Asian region using ERA-5 reanalysis data. We report that specifically split-downward propagating SSWs (dSSWs) cause enormous ozone enhancement in the upper troposphere and lower stratosphere (UTLS) over South Asia around the dSSW-onset, with a maximum of ~290 % within ±30 days. The ozone intrusions propagate deep into the troposphere, causing near-surface maximum ozone increase by 43 % within ±30 days around the SSW-onset. The ozone enhancement increases ozone radiative forcing in the troposphere by 0.04±0.03 W.m^-2 and UTLS by 0.08±0.06 W.m^-2 over South Asia. Frequent SSW events in a warming climate will thus likely increase stratospheric ozone intrusions and ozone radiative forcing over South Asia, potentially exacerbating regional climate warming. The elevated tropospheric ozone amounts due to stratospheric intrusions are posing threat to humans and vegetation.