Change in Tropospheric Ozone in the Recent Decades and Its Contribution to Global Total Ozone. Issue 22 (16th November 2022)

• Record Type: Journal Article
• Authors: Liu, Junhua; Strode, Sarah A.; Liang, Qing; Oman, Luke D.; Colarco, Peter R.; Fleming, Eric L.; Manyin, Michael E.; Douglass, Anne R.; Ziemke, Jerald R.; Lamsal, Lok N.; Li, Can
• Is Part Of: Journal of geophysical research. Volume 127:Issue 22(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-11-16
• Subjects: total ozone trends -- tropospheric ozone trends -- ozone precursors; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2022JD037170
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Tropospheric ozone is a key chemically active trace gas and radiative forcer. Understanding its long‐term changes is important to properly interpret observed changes in total column ozone and stratospheric ozone recovery. We investigate global and regional tropospheric ozone changes and their impact on total column ozone during 2005–2018 using satellite measurements and the NASA Goddard Earth Observing System Chemistry Climate Model (GEOSCCM). Global total ozone increased ∼4 DU during 2005–2018 (+0.28 ± 0.06 DU yr −1 ) as inferred from Ozone Monitoring Instrument (OMI). Consistent with previous studies, the OMI/MLS (Microwave Limb Sounder) derived global tropospheric ozone increased 2.2 DU during this period, 60% of the global total column ozone increase. While GEOSCCM reproduces reasonably well the total column increase, it overestimates the stratospheric ozone increase and underestimates the tropospheric ozone increase. We find that the tropospheric ozone increases are likely attributed to a growth of regional emissions of key ozone precursors, especially volatile organic compounds as reflected by the positive trends in formaldehyde (CH2 O). Although carbon monoxide (CO) has been decreasing everywhere around the globe, it has relatively small impact on the tropospheric ozone trend. Trends in nitrogen dioxide (NO2 ) vary with regions, and these changes counteract or reinforce the positive effects of CH2 O on the tropospheric ozone increases. The model underestimates the observed tropospheric ozone increase, especially over the US and Europe, because of underestimated NO2 emissions changes used in the model. The stratospheric ozone contribution increases during this period in the Northern Hemisphere and contributes to the tropospheric ozone increase. Plain Language Summary: The ozone layer in the stratosphere plays an important role in shielding the biosphere from harmful solar ultraviolet radiation. Changes in total ozone column are commonly used as representative of the ozone layer changes as most of the ozone resides in the lower stratosphere. However, changes in tropospheric ozone can be a confounding factor of detecting and attributing ozone trends during recent decades. Here we use a model‐data combined analysis to quantify tropospheric ozone change and its contribution to total column ozone change. Our results based on satellite measurements show that the global total column ozone increased a few DU during the recent two decades, and a significant part of this increase is attributed by the increase in the tropospheric column ozone. We also find that tropospheric ozone increases depend primarily on changes in ozone precursors, especially volatile organic compounds, which are attributed to a growth of regional anthropogenic emissions. Key Points: Global total column ozone increased about 4 DU from 2005 to 2018 and about 60% of this increase due to tropospheric ozone Tropospheric ozone increases depend primarily on increased regional emissions of ozone precursors, for example, volatile organic compounds The Goddard Earth observing system chemistry climate model underestimates the observed tropospheric ozone increase, as a result of underestimated NO2 emissions increase