Connections between the Surface-Level Ozone-Temperature Relationship and the Eddy-Driven Jet Stream

Observational and modeling studies report nearly ubiquitously a positive relationship between surface-level temperature and ozone (O₃): an increase in temperature leads to an increase in O₃. We investigate this relationship in the Northern Hemisphere during boreal summer (JJA). While our findings support these previous studies, which have largely focused on industrialized areas in the mid-latitudes, we find the relationship between O₃ and temperature to be varied outside the mid-latitudes in both observations and chemistry transport model (CTM) simulations, and we identify large regions outside the mid-latitudes characterized by a very weak or even negative O₃-temperature relationship. This spatial pattern appears to be linked to the latitude of the eddy-driven jet stream. Within a latitudinal band roughly 15° poleward and equatorward of the mean latitude of the jet, both O₃ and temperature increase with poleward movement of the jet, and there is a positive O₃-temperature relationship. Outside of this band, O₃ and temperature behave differently to shifts of the jet, and there is a weak or negative O₃-temperature relationship. CTM experiments with time-invariant chemistry and idealized tracers suggest that transport - not chemistry or emissions - drives this relationship, which persists across seasons and for non-photochemically reactive species with different source regions. Our analysis indicates that the jet-surface O₃ connections occur due to movement of cyclones and anticyclones with the jet. These results suggest that the relationship between O₃ and temperature is much more intricate than higher temperatures simply leading to faster photochemical reaction rates or increased emissions: rather, changes in temperature must also be cast in terms of their changes in synoptic-scale transport regimes.