Sensing air pollution from space: Detecting smog-forming chemistry

#Geoscience #& #Remote #Sensing #Society

Controlling ground-level ozone smog has proven to be a persistent challenge in many U.S. air quality jurisdictions.  Ozone is a secondary air pollutant that forms through atmospheric chemistry and depends non-linearly on precursor emissions of nitrogen oxides (NO_x) and volatile organic compounds (VOC).  The highest concentrations generally occur during the warm season, when ozone production tends to be limited by the availability of NOx, with the exception of some urban areas with high NO_x emissions.  Implementation of effective emission control programs requires knowledge of the sensitivity of ground-level ozone in a particular metropolitan area to NO_x versus VOC emissions.  Since the mid-1990s, satellite instruments have retrieved two chemical species (nitrogen dioxide and formaldehyde) that can serve as proxies for these precursor emissions.  Following a brief introduction to the approaches developed to diagnose ozone formation chemistry from space, I will highlight a recent study identifying long-term trends in the ozone formation chemistry in several U.S. cities from satellite products.  Finally, I will share some ongoing work connecting space-based and ground-level viewpoints during summer 2018 field campaigns in the New York City and Baltimore/D.C. regions, with an emphasis on changes in ozone sensitivity to its precursor emission on days when the National Ambient Air Quality Standard for ozone is exceeded.