Informing Near-Airport Satellite NO Retrievals Using Pandora Sky-Scanning Observations.

Airports are a large and growing source of NO . Tracking airport-related emissions is especially difficult, as a portion of emissions are elevated above the surface. While satellite-based NO observations show hot-spots near airports, near-source retrievals often have large biases related to uncertainties in the NO vertical distribution and resultant air mass factors (AMF). Here we use observations from UV-vis spectrometers (Pandora 1S, SciGlob) deployed near the Atlanta Hartsfield-Jackson International airport from April 2020-May 2021 to assess the impact of aviation on NO vertical profiles. We show the first near-airport sky-scanning Pandora observations, which are used to distinguish the airport plume from the urban background. We find that increasing aviation leads to higher NO over the airport, and the enhancement is distributed across the mixed layer near-equally. We compare observed profiles with those modeled by the Goddard Earth Observing System composition forecast (GEOS-CF) system. We find that modeled profiles attribute a larger portion of the column closer to the surface and underestimate the NO mixing height. Observed profiles typically exhibited greater NO concentrations up to 2.5 km above ground level. Air mass factors (AMF) calculated using observations (AMF) are similar over Hartsfield-Jackson to those calculated using GEOS-CF (AMF). The unexpected similarity in alternative AMFs is attributed to the altitude-dependent sensitivity of AMF to changes in NO concentration. Using either AMF or AMF to evaluate TROPOMI NO against independent direct-sun observations produces consistent normalized mean differences of -22% and -29%, respectively. Overall, these results demonstrate the benefits of a combined ground and satellite-based approach for probing a complex distribution of NO emissions in an urban area.