Emerging Patterns of O3 Sensitivity to CO over Megacities Derived from Satellite Retrievals
Résumé
The availability of long term multispecies retrievals offers an opportunity to study spatiotemporal patterns of atmo- spheric composition, especially over large anthropogenic pollution regions. Here, we jointly analyze IASI retrievals of O3 and CO (along with OMI NO2) to explore additional observational constraints on anthropogenic pollution. In particular, we estimate the trends of the enhancement ratios derived from IASI O3 and CO and OMI NO2 over major combustion regions in China and United States. Our results show intriguing differences of dO3/dCO across Chinese megacities. In particular, Beijing and Shenzhen shows a positive linear trend (0.58±2.15 and 0.38±0.42 %/yr respectively) while Shanghai shows a negative trend (-062±0.67%/yr). This may be attributed to differences in VOC-NOx-O3 regime between these cities, which predictive models of atmospheric composition should be able to capture. On the other hand, enhancements of O3 derived from these ratios show a pattern of decreasing to increasing trend across Beijing, Shanghai, and Shenzhen which may indicate differences in combustion-related activity between these cities consistent with the developing economic status of these cities. We suggest further evaluation against other datasets (ground- based, airborne, or other retrievals) to enhance the rigor of these find- ings. Nevertheless, this study offers an impetus towards characterizing other species relationships (e.g., IASI NH3, CH4, CO2) not only as basis for monitoring consistency in atmospheric composition but also as a way to fully utilize the information content of these retrieval products in the context of data assimilation and reanalysis.