Ozone production in transpacific Asian pollution plumes and implications for ozone air quality in California

Abstract

We examine the ozone production efficiency in transpacific Asian pollution plumes, and the implications for ozone air quality in California, by using aircraft and surface observations in April–May 2002 from the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) campaign off the California coast and the Pacific Exploration of Asian Continental Emission–B (PEACE‐B) campaign over the northwest Pacific. The observations are interpreted with a global three‐dimensional chemical transport model (GEOS‐CHEM). The model reproduces the mean features observed for CO, reactive nitrogen oxides (NOy), and ozone but underestimates the strong (∼20 ppbv) stratospheric contribution to ozone in the middle troposphere. The ITCT 2K2 aircraft sampled two major transpacific Asian pollution plumes, one on 5 May at 5–8 km altitude with CO up to 275 ppbv but no elevated ozone and one on 17 May at 2.5–4 km altitude with CO up to 225 ppbv and ozone up to 90 ppbv. We show that the elevated ozone in the latter plume is consistent with production from peroxyacetylnitrate (PAN) decomposition during subsidence of the plume over the northeast Pacific. This production is particularly efficient because of the strong radiation and low humidity of the subsiding environment. We argue that such PAN decomposition represents a major and possibly dominant component of the ozone enhancement in transpacific Asian pollution plumes. Strong dilution of Asian pollution plumes takes place during entrainment in the U.S. boundary layer, greatly reducing their impact at U.S. surface sites. California mountain sites are more sensitive to Asian pollution because of their exposure to the free troposphere. Model results indicate a mean Asian pollution enhancement of 7 ppbv ozone at Sequoia National Park in May 2002 on those days when the 8‐hour average ozone concentration exceeded 80 ppbv.

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

“…Photochemical impact remains uncertain. Clearly, long-range-transported biomass burning plumes can influence Europe (Cook et al, 2007;Real et al, 2007), though the impact is variable (Hudman et al, 2004). More recently, European fires in Portugal and Russia have been shown to contribute to air pollution (Tressol et al, 2008;Martins et al, 2012), and the frequency is expected to increase with climate change (Carvalho et al, 2011).…”

Ground‐level nitrogen dioxide concentrations inferred from the satellite‐borne Ozone Monitoring Instrument

“…[13] Several previous studies have used GEOS-Chem to interpret in situ measurements of reactive nitrogen Wang et al, 2004;Hudman et al, 2004Hudman et al, , 2007Martin et al, 2006] as well as observations of tropospheric NO 2 columns from satellite instruments [Martin et al, 2003a[Martin et al, , 2004bJaeglé et al, 2005;Guerova et al, 2006;Sauvage et al, 2007;Wang et al, 2007bWang et al, , 2007aBoersma et al, 2008aBoersma et al, , 2008bBucsela et al, 2008]. GEOS-Chem simulations generally agree to within 30% of measured NO x , HNO 3 , and PAN over eastern North America Hudman et al, 2007;Singh et al, 2007] [15] Figure 1 shows seasonal mean tropospheric NO 2 columns from OMI and GEOS-Chem.…”

Surface ozone background in the United States: Canadian and Mexican pollution influences

“…These remote concentrations have increased over the past decades (Lin et al, 2000;Jaffe and Ray, 2007), due at least in part to hemispheric-scale pollution (Fiore et al, 2002a). A number of model studies have examined the effects on US ozone air quality of emissions in Asia (Jacob et al, 1999;Hudman et al, 2004), Europe (Li et al, 2002), and global methane (Fiore et al, 2002b), but there has been little investigation of the nearer-scale international influences from Canada and Mexico. We examine these influences here and the implications for meeting US ozone air quality standards, for both present and projected future (2020) conditions.…”

“…Ozone has a lifetime of only a few days in the continental boundary layer in summer but several weeks in the free troposphere (Wang et al, 1998;Fiore et al, 2002a), so that ozone pollution ventilated from the continental boundary layer can be transported on intercontinental scales. Ozone is also produced in the remote troposphere from methane and NO x , both of which have large anthropogenic sources (Wang et al, 1998;Fiore et al, 2002b;Hudman et al, 2004).…”