Response of the global surface ozone distribution to Northern Hemisphere sea surface temperature changes: implications for long-range transport

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Yi, Kan, Liu, Junfeng, Ban-Weiss, George, Zhang, Jiachen, Tao, Wei, Cheng, Yanli, Tao, Shu
• Format: Text
• Language: English
• Published: 2018
• Subjects: Pacific; Indian; North Atlantic
• Online Access: https://doi.org/10.5194/acp-17-8771-2017; https://www.atmos-chem-phys.net/17/8771/2017/

The response of surface ozone (O 3 ) concentrations to basin-scale warming and cooling of Northern Hemisphere oceans is investigated using the Community Earth System Model (CESM). Idealized, spatially uniform sea surface temperature (SST) anomalies of ±1 °C are individually superimposed onto the North Pacific, North Atlantic, and North Indian oceans. Our simulations suggest large seasonal and regional variability in surface O 3 in response to SST anomalies, especially in the boreal summer. The responses of surface O 3 associated with basin-scale SST warming and cooling have similar magnitude but are opposite in sign. Increasing the SST by 1 °C in one of the oceans generally decreases the surface O 3 concentrations from 1 to 5 ppbv. With fixed emissions, SST increases in a specific ocean basin in the Northern Hemisphere tend to increase the summertime surface O 3 concentrations over upwind regions, accompanied by a widespread reduction over downwind continents. We implement the integrated process rate (IPR) analysis in CESM and find that meteorological O 3 transport in response to SST changes is the key process causing surface O 3 perturbations in most cases. During the boreal summer, basin-scale SST warming facilitates the vertical transport of O 3 to the surface over upwind regions while significantly reducing the vertical transport over downwind continents. This process, as confirmed by tagged CO-like tracers, indicates a considerable suppression of intercontinental O 3 transport due to increased tropospheric stability at lower midlatitudes induced by SST changes. Conversely, the responses of chemical O 3 production to regional SST warming can exert positive effects on surface O 3 levels over highly polluted continents, except South Asia, where intensified cloud loading in response to North Indian SST warming depresses both the surface air temperature and solar radiation, and thus photochemical O 3 production. Our findings indicate a robust linkage between basin-scale SST variability and continental surface O 3 pollution, which should be considered in regional air quality management.