Transport of Peroxyacyl Nitrates (PANs) Across Northern Hemisphere Ocean Basins From Satellite Observations

Abstract We leverage global satellite observations of Peroxyacyl Nitrates (PANs) from the Cross‐track Infrared Sounder (CrIS) on the Suomi National Polar‐orbiting Partnership satellite to evaluate seasonal and interannual variations of intercontinental transport in the Northern Hemisphere between 2016 and 2022. April and July are dominant months for transpacific transport of PANs, and summer months (June, July, and August) are dominant for transatlantic transport. Significant interannual variability occurs during months with peak PANs transport. We combine CrIS PANs and Ozone Monitoring Instrument (OMI) NO 2 to explore changes in intercontinental PANs transport associated with COVID‐19‐related emissions reductions. CrIS indicates statistically meaningful decreases in PANs over Pacific and Atlantic oceans compared to Pre‐COVID years (2016–2019), with changes in PANs smaller than those in NO 2 . May 2020 CrIS observations indicate that PANs (OMI NO 2 ) declined over the NW Pacific by ∼11% (∼33%), NE Pacific by ∼8% (∼15%), USA‐Atlantic outflow by ∼4% (∼4%), and Atlantic by ∼11% (∼11%). The largest change in PANs occurred over the NW Pacific in February 2020, where PANs (OMI NO 2 ) decreased ∼16% (∼42%). A chemical transport model is used to simulate PAN changes in response to the pandemic emissions changes, and the model is consistent with the observations. Our observations suggest that PANs over the ocean basins have not fully rebounded to Pre‐COVID values, consistent with the trend in tropospheric column NO 2 .