TEMPO Applications During Poor Wintertime Air Quality in Salt Lake City: An Analysis of Persistent Cold Air Pooling Events

Abstract

During the wintertime, the Salt Lake Valley (SLV) experiences episodes of poor air quality during persistent cold air pools (PCAPs), wherein the atmospheric boundary layer remains stable for several days. We examine insights into the accumulation of primary emissions during PCAPs gained from NO ₂ tropospheric column abundances derived from Tropospheric Emissions: Monitoring of Pollution (TEMPO), the first geostationary satellite to monitor trace gases over North America. We employ measurements from ground‐based Pandora spectrometers to evaluate the ability of TEMPO to sample these pollution events. We find that TEMPO performs well when compared to the Pandora measurements ( r  = 0.72–0.82, with average biases between ∼4% and 6%). Importantly, we confirm that TEMPO‐based sampling does not change significantly during PCAPs compared to background winter conditions. We use TEMPO data to create maps of NO ₂ air pollution over the SLV, highlighting the areas where the buildup is most severe during PCAPs. To evaluate the relevance of TEMPO observations to exposure estimates, we compare tropospheric NO ₂ to surface concentrations collected at state monitoring sites. The spatial correlations over the course of the day are very strong ( r  = 0.75–0.94 depending on hour), but we observe asynchrony in the diurnal cycle of NO ₂ at the surface and in the column. Our results demonstrate that TEMPO performs well at capturing wintertime pollutant accumulation in this challenging environment and provides insights into how TEMPO can be used to supplement ground‐based NO ₂ networks or emission estimates even during extreme wintertime pollution events.