Chemical Dynamics Driving NO2 in the Lower Troposphere at Rural Sites During DISCOVER-AQ: A Comparison Between an Inland Wintertime Site and a Coastal Summertime Site

Title: Chemical Dynamics Driving NO2 in the Lower Troposphere at Rural Sites During DISCOVER-AQ: A Comparison Between an Inland Wintertime Site and a Coastal Summertime Site.

Authors: Felicia Guarriello, Deborah C Stein Zweers, Richard Clark

Abstract: DISCOVER-AQ is a NASA funded field project aimed at gathering air quality data to better understand the links between pollution near the ground where people live and breathe and pollution higher in the troposphere. These projects take place at various sites including the agricultural, inland site of Huron, CA (January – February 2013) and coastal Smith Point, TX (September 2013). A unique sonde instrument has been developed at KNMI (Royal Netherlands Meteorological Institute) to measure nitrogen dioxide (NO2) at the ground level and also create a high-resolution vertical profile. This sonde was attached to a tethered balloon and took NO2 measurements in the planetary boundary layer while an aircraft carrying an airborne atmospheric chemical laboratory made measurements as it spiraled down from above. These measurements allowed us to obtain a unique set of NO2 profiles that effectively link the surface to the lower troposphere.

The data from these two sites, an inland wintertime site and a coastal summertime site, can be compared to learn more about the chemical dynamics that drive near-surface nitrogen dioxide concentrations. A comparative description is given for the various constituents of the NO2 budget measured at each site along with relevant meteorological parameters and net surface radiation. Initial results from ground and aircraft data at Huron, CA suggest that NOy species may play an important role in understanding the day-to-day and diurnal variations in near-surface NO2 at this site. Additional measurements that will be made on the ground at Smith Point, TX will allow us to investigate the role of NOy in even greater detail. We present unique near-surface NO2 datasets measured during different seasons at two locations and describe and evaluate the unique atmospheric chemical dynamics at each site. Such information can lead to improved knowledge of the air quality for different spatial regimes. This can, in turn lead to increased awareness and improvements in human health.