Observability and Frequency of Spatial and Temporal Gradients Relevant to Air Quality During DISCOVER-AQ

The Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument will be the first NASA mission to make atmospheric composition observations from geostationary orbit and partially fulfills the goals of the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission. Using high-resolution model output and in-situ measurements taken during the four deployments of the NASA Earth Venture mission DISCOVER-AQ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality), we use structure function analyses to quantify how often the atmosphere exhibited observationally relevant gradients in several key trace gas species (O3, NO2, CO, SO2, and HCHO), over what length scales they occurred, and over what time periods. These deployments consisted of month-long campaigns over Baltimore, MD (Jul 2011), the San Joaquin Valley, CA (Jan-Feb 2013), Houston, TX (Sep 2013), and Denver, CO (Jul-Aug 2014) and represent a wide variety of emissions sources, meteorological conditions, and air quality conditions. Using the precision requirements defined by the science traceability matrices of these space-borne missions, we assess the detectability and frequency of spatial and temporal gradients relevant to air quality observations. For example, over the Baltimore/DC corridor spatial gradients in NO2 were larger than the prospective precision requirements outlined for TEMPO, and therefore hypothetically observable to the instrument, 95% of the time during July 2011. We additionally compare the spatial and temporal variability of the surface mixing ratio and boundary layer column to that of the tropospheric column.