Surface Ozone‐Meteorology Relationships: Spatial Variations and the Role of the Jet Stream. Issue 21 (3rd November 2020)

• Record Type: Journal Article
• Authors: Kerr, Gaige Hunter; Waugh, Darryn W.; Steenrod, Stephen D.; Strode, Sarah A.; Strahan, Susan E.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 21(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-03
• Subjects: surface ozone -- jet stream -- temperature -- humidity -- mean meridional circulation -- cyclones; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2020JD032735
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: We investigate the relationships among summertime ozone (O3 ), temperature, and humidity on daily timescales across the Northern Hemisphere using observations and model simulations. Temperature and humidity are significantly positively correlated with O3 across continental regions in the midlatitudes (∼35–60°N). Over the oceans, the relationships are consistently negative. For continental regions outside the midlatitudes, the O3 ‐meteorology correlations are mixed in strength and sign but generally weak. Over some high latitude, low latitude, and marine regions, temperature and humidity are significantly anticorrelated with O3 . Daily variations in transport patterns linked to the position and meridional movement of the jet stream drive the relationships among O3, temperature, and humidity. Within the latitudinal range of the jet, there is an increase (decrease) in O3, temperature, and humidity over land with poleward (equatorward) movement of the jet, while over the oceans poleward movement of the jet results in decreases of these fields. Beyond the latitudes where the jet traverses, the meridional movement of the jet stream has variable or negligible effects on surface‐level O3, temperature, and humidity. The O3 ‐meteorology relationships are largely the product of the jet‐induced changes in the surface‐level meridional flow acting on the background meridional O3 gradient. Our results underscore the importance of considering the role of the jet stream and surface‐level flow for the O3 ‐meteorology relationships, especially in light of expected changes to these features under climate change. Plain Language Summary: The relationship of ozone (O3 ) with meteorological variables such as temperature and humidity at the Earth's surface varies in strength and sign. Some regions, such as continental parts of the midlatitudes, experience increases in O3 as the temperature or humidity rises. However, this is not the case over the entire Northern Hemisphere. We use detailed computer simulations of atmospheric chemistry to show that these relationships are primarily the result of changes in meteorology, not changes in emissions or chemistry. The relationship between O3 and meteorological variables is related to the north‐south movement of the jet stream, powerful eastward‐flowing air currents located near the tropopause that can encircle the hemisphere. Specifically, we find that the jet stream influences the O3 ‐meteorology relationships due to its effect on the northward and southward advection of O3, temperature, and humidity and not due to cyclones and the associated frontal activity, as has been previously suggested. Our results are relevant for understanding the present‐day O3 ‐meteorology relationships and how climate change may impact O3 pollution. Key Points: The relationships among summertime O3, temperature, and humidity vary over the Northern Hemisphere Daily variations in meteorology drive the O3 ‐meteorology covariance The jet impacts meridional flow, which acts on the latitudinal O3 gradient and leads to variations in the O3 ‐meteorology relationships