Impact of Asian emissions on observations at Trinidad Head, California, during ITCT 2K2

Abstract

[1] Field measurements of a wide suite of trace gases and aerosols were carried out during April and May 2002, along with extensive chemical transport modeling, as part of the NOAA Intercontinental Transport and Chemical Transformation study. Here, we use a combination of in-situ ground-based measurements from Trinidad Head, CA, chemical transport modeling, and backward trajectory analysis to examine the impact of long-range transport from Asia on the composition of air masses arriving at the California coast at the surface. The impact of Asian emissions is explored in terms of both episodic enhancements and contribution to background concentrations. We find that variability in CO concentrations at the ground site was largely driven by North American emissions, and that individual Asian plumes did not cause any observable pollution enhancement episodes at Trinidad Head. Despite this, model simulations suggest that Asian emissions were responsible for 33% of the CO observed at Trinidad Head, providing a larger mean contribution than direct emissions from any other region of the globe. Surface ozone levels were found to depend primarily on local atmospheric mixing, with surface deposition leading to low concentrations under stagnant conditions. Model simulations suggested that on average 4 ± 1 ppb of ozone (10% of observed) at Trinidad Head was transported from Asia.

Transpacific transport of benzo[a]pyrene emitted from Asia

“…During this period the Intercontinental Transport and Chemical Transformation (ITCT 2K2) experiment was also conducted, during which the concentrations of different pollutants were measured by an aircraft campaign over the West Coast of the United States (near Monterey, California). Results from this field campaign are discussed elsewhere (Allan et al, 2004;de Gouw et al, 2004;Goldstein et al, 2004;Nowak et al, 2004). At the MBO site, the modeled concentrations were poorly correlated with measured concentrations (r=0.09),likely because of the high altitude (2700 m a.s.l.)…”

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

“…Lefohn et al (2001) pointed out that ozone concentrations at remote US sites in winter-spring are often in the 50-60 ppb range, so that air quality standards close to those values would be difficult to achieve. However, Fiore et al (2002a) pointed out that these values are not representative of surface air in summer, Using a global chemical transport model (CTM), they estimated a PRB of 15-35 ppbv in the US during summer with little variability, and demonstrated consistency with observations at remote sites (Fiore et al, 2002a;Goldstein et al, 2004).…”

Changes in the photochemical environment of the temperate North Pacific troposphere in response to increased Asian emissions

“…Six intensive research campaigns spanning 18 years provide measurements in the eastern North Pacific and along the U.S. West Coast. Coastal, surface measurements were made at Point Arena, California, in 1985, at Cheeka Peak, Washington, in 1997, 1998and 2002 and at Trinidad Head, California, during the Intercontinental Transport and Chemical Transformation study in 2002 (ITCT 2K2) Goldstein et al, 2004]. Three aircraft research campaigns were conducted: the National Aeronautics and Space Administration (NASA) Global Tropospheric Experiment (GTE) Chemical Instrumentation and Evaluation (CITE) 1C study in 1984 [Beck et al, 1987], the Photochemical Ozone Budget of the Eastern North Pacific Atmosphere (PHOBEA) studies in 1999, 2001, and 2002 and the ITCT 2K2 study in 2002.…”