Evaluating the Influence of Entrainment on Surface Ozone in the Colorado Front Range

Abstract:

Ozone concentrations at the earth’s surface are influenced by both meteorological and chemical processes and are in particular a function of advection, entrainment, deposition, chemical production and loss. Understanding these mechanisms controlling surface ozone concentrations is an essential component for designing effective control measures. However, determining the magnitude of these processes contributing to the total ozone budget generally comes with high uncertainties resulting from the diversity of data required.

Most ground site measurements are insufficient to quantify the influence of long range transported or residual layer ozone on surface concentrations, as information above the boundary layer is difficult to obtain. On the other hand, aircraft observations often lack either the essential surface information, sufficient sampling repetition over the site, or a full range of chemical measurements. The data set collected during the Colorado FRAPPE/DISCOVER-AQ initiative is very rich, as several ground sites were equipped with a suite of chemical and meteorological measurements and multiple aircraft sampled the column above up to three times a day over a whole month.

Here we combine data from the ground sites and aircraft to calculate the full boundary layer ozone budget to quantify the relative importance of the different budget terms. In the Colorado Front Range both long range transported ozone and local sources likely play important roles. In addition, a similar budget analysis performed for a 3-D WRF-Chem simulation offers insight into whether WRF-modeled data agrees with the measurements as to each budget term’s importance in controlling surface ozone concentrations.