Trace Gas and Particle Measurements Made at Rural Sites During DISCOVER-AQ: A Comparison of Trends Between an Inland Wintertime Site and a Coastal Summertime Site

Abstract:

The NASA DISCOVER-AQ field projects aim to characterize regional air quality in both the horizontal and vertical dimensions. The campaigns feature several key measurement sites including the rural locations of Huron, CA from January-February 2013 and Smith Point, TX during September 2013. To meet campaign objectives, it is essential to continuously observe trace gases, aerosols, and meteorological variables at ground sites. These variables were measured using EPA-standard trace gas analyzers for NO/NO₂/NO_x and O₃ (ppb), a nephelometer for backscattering and total scattering coefficients (m^-1), and a flux tower for near surface meteorological parameters. The trace gas analyzers and the nephelometer recorded data in one-minute averages, while the flux tower recorded data in five-minute averages.

Comparisons will be made between the California and the Texas trace gas and scattering measurements. Based on observations made at the California site, NO/NO₂/NO_x generally vary similarly on a given diurnal cycle, with a peak in NO_x during late afternoon (PST), while O₃ peaks during mid-afternoon. Conversely, the scattering coefficients dip during late morning, rapidly increase mid-day, dip again during late afternoon, and increase once more during the late night. A discussion of the day-to-day variability at each site is given and linked to local meteorological conditions and synoptic-scale changes. Linking the overall meteorological conditions to the trace gas and aerosol concentrations can lead to identification of local and regional source regions. This information can inform regional air quality policy and, in turn, aid the mitigation of regional air pollution and improve the overall health of the population in that area.