Xiaomeng Jin1, Arlene Fiore1, Lee Murray2, Luke Valin3 Image Credit:  NASA's Goddard Space Flight Center Evaluating a space-based indicator of surface ozone sensitivity to emissions of NOx vs. NMVOC and applications to decadal trends Xiaomeng Jin1, Arlene Fiore1, Lee Murray2, Luke Valin3 1. Lamont-Doherty Earth Observatory of Columbia University 2. Dept. of Earth and Environmental Sciences, University of Rochester 3. U.S. EPA Office of Research and Development, Research Triangle Park

Observing surface O3-NOx-VOC sensitivity from space: HCHO/NO2 (FNR) ? NOx-Limited NOx ⬆ O3 ⬆ VOC ⬆ O3 ✕ > 2 Control Vertically Integrated OMI HCHO/NO2 (FNR) Martin et al., (2004); Duncan et al., (2010) NO2 column HCHO Column AURA Satellite VOC NOx Surface O3 ? NO2 HCHO Sillman (1995) ? VOC-Limited (NOx-Saturated) VOC ⬆ O3 ⬆ NOx ⬆ O3 ⬇ < 1 Control ? ?

d[O3]/dENOx > d[O3]/dEvoc d[O3]/dENOx > d[O3]/dEvoc Deriving regime threshold values from GEOS-Chem (v9-02) emission perturbation simulations -20% ENOx -20% ENOx d[O3]/dE (s/cm) d[O3]/dE (s/cm) -20% EVOC -20% EVOC NOx-Saturated d[O3]/dENOx<0 NOx-Saturated d[O3]/dENOx<0 NOx-Lmited d[O3]/dENOx > d[O3]/dEvoc NOx-Lmited d[O3]/dENOx > d[O3]/dEvoc Surface HCHO/NO2 Column HCHO/NO2

GEOS-Chem reveals different column-to-surface relationships of HCHO and NO2 We apply the MODELED column-to-surface scaling factor to the more robust regime threshold values of surface HCHO/NO2. The resulting regime threshold values of column HCHO/NO2 vary in space and time. Jin et al., submitted

The same OMI observation, different answers Spatial and temporal correlation between model and space-based HCHO/NO2 depends on NO2 product. Mean difference depends on HCHO product. vs. Jin et al., submitted

Monthly OMI HCHO/NO2 over New York City Increasing NOx sensitivity over the NE United States as emissions decline May OMI HCHO/NO2 OMI observation detects the transition to NOx-limited regime has shifted one- month earlier from 2005 to 2015 over New York City. Implies continued efficacy of ground-level ozone abatement via regional NOx emission control programs. 2005 2015 Monthly OMI HCHO/NO2 over New York City Jin et al., submitted

Summary: OMI HCHO/NO2 can detect the evolution of O3-NOx-VOC sensitivity (but with uncertainty) Seasonal and spatial variations in the column-to- surface relationship should be considered when diagnosing ozone production regimes from space. OMI observation shows increasing NOx sensitivity over the U.S.A, Europe, Japan, Korea and megacities in China from 2005 to 2015. Issues: Large uncertainty at daily scale. The spatial resolution of OMI is unable to reveal O3 photochemistry at urban cores.

Europe: Increasing NOx sensitivity over urban areas June OMI HCHO/NO2 over Europe O3 production is becoming more sensitive to NOx emissions over London, Paris, Moscow. Larger uncertainties of satellite retrieval over Europe. Column-based observation weakens the seasonal cycle of O3-NOx-VOC sensitivity. 2005 2015 Monthly OMI HCHO/NO2 over Paris Jin et al., submitted

East Asia: Heterogeneous trend of O3-NOx-VOC sensitivity May OMI HCHO/NO2 over East Asia Spatial and temporal expansion of VOC-limited regime due to increasing NOx emissions, suggesting the importance of VOC emission control (Jin and Holloway, 2015) Three exceptions in China: Beijing, Shanghai and Pearl River Delta. Increasing NOx sensitivity in Tokyo and Seoul. 2005 2015 Monthly OMI HCHO/NO2 over Guangzhou Jin et al., submitted

Seasonal variation of Column-to-surface scaling factor of HCHO/NO2

Vertical Profiles of NO2 and HCHO in GEOS-Chem

Ozone Isopleth