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Inferring changes in summertime surface ozone-NOx-VOC chemistry over U.S. urban areas from two decades of satellite and ground-based observations
Citation:
Jin, X., A. Fiore, K. Boersma, I. De Smedt, AND L. Valin. Inferring changes in summertime surface ozone-NOx-VOC chemistry over U.S. urban areas from two decades of satellite and ground-based observations. International Journal of Environmental Science and Technology. Springer, Heidelburg, Germany, 54(11):6518-6529, (2020). https://doi.org/10.1021/acs.est.9b07785
Impact/Purpose:
Urban ozone (O3) formation can be limited by NOx, VOCs, or both, complicating the design of effective O3 abatement plans. A satellite-retrieved ratio of formaldehyde to NO2 (HCHO/NO2), developed from theory and modeling, has previously been used to indicate O3 formation chemistry. Here, we connect this space-based indicator to spatiotemporal variations in O3 recorded by on-the-ground monitors over major U.S. cities.
Description:
Urban ozone (O3) formation can be limited by NOx, VOCs, or both, complicating the design of effective O3 abatement plans. A satellite-retrieved ratio of formaldehyde to NO2 (HCHO/NO2), developed from theory and modeling, has previously been used to indicate O3 formation chemistry. Here, we connect this space-based indicator to spatiotemporal variations in O3 recorded by on-the-ground monitors over major U.S. cities. High-O3 events vary non-linearly with OMI HCHO and NO2, and the transition from VOC-limited to NOx-limited O3 formation regimes occurs at higher HCHO/NO2 value (3 to 4) than previously determined from models, with slight inter-city variations. To extend satellite record back to 1996, we develop an approach to harmonizing observations from GOME and SCIAMACHY that accounts for differences in spatial resolution and overpass time. Two-decade (1996 - 2016) multi-satellite HCHO/NO2 captures the timing and locations of the transition from VOC-limited to NOx-limited O3 production regime in major U.S. cities, which aligns with the observed long-term changes in urban-rural gradient of O3 and the reversal of O3 weekend effect. Our findings suggest promise for applying space-based HCHO/NO2 to interpret local O3 chemistry, particularly with the new-generation satellite instruments that allow evaluations at finer spatial and temporal resolution.
URLs/Downloads:
DOI: Inferring changes in summertime surface ozone-NOx-VOC chemistry over U.S. urban areas from two decades of satellite and ground-based observations
https://pubs.acs.org/doi/10.1021/acs.est.9b07785