Vertical profiles of O₃, aerosols, CO and NMHCs in the Northeast Pacific during the TRACE‐P and ACE‐ASIA experiments

Abstract

Airborne observations of NMHCs, O3, CO, and aerosol scatter were made near the coast of Washington State from 29 March to 6 May 2001 as part of the Photochemical Ozone Budget of the Eastern North Pacific‐II (PHOBEA‐II) experiment. These observations overlapped the time period of the TRACE‐P (24 February to 10 April 2001) and ACE‐ASIA (27 March to 30 April 2001) experiments operating in the Western Pacific. Measurements were made during 12 flights at 48.31 ± 0.03°N latitude, 124.63 ± 0.08°W longitude at altitudes from 0 to 6 km. On several flights, significant enhancements in all species were observed and are attributed to transport from the Eurasian continent, including a long‐range transport event observed on 14 April 2001. This event contained substantial CO, NMHC, and aerosol loadings and was identified by the Total Ozone Mapping Spectrometer (TOMS) aboard the Earth Probe Satellite and airborne and surface measurements throughout North America. This airmass was unique in that it contained the highest levels of aerosol scatter, CO, and various NMHCs observed in 2001, was the only flight with a low Ångstrom coefficient (0.7) indicating dominance of super micron aerosols, and had a negative relationship between ozone and aerosol scatter (r = −0.30). Within this mineral dust and pollution layer, aerosol scatter, propane, and CO were enhanced by 1054%, 85%, and 36%, respectively, over the observed spring 2001 median values between 3.5 and 6 km. A comparison of our previous aircraft campaign in 1999 with 2001 observations shows that ozone, aerosol scatter, and most NMHCs were significantly lower in the spring of 2001. The exact cause is still under investigation, but the combination of elevated ozone, aerosol scatter, and NMHCs suggests a combustion source that was enhanced and/or transported more efficiently during the spring of 1999.

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

“…Nominal reported accuracies and precisions are, e.g., ±5% and the larger of ±1% or 2 pptv, respectively, for the PEM-West B study [Hoell et al, 1997]. Further details can be found in the original papers describing the alkane measurement techniques: Point Arena [Singh et al, 1988], PEM-West B [Blake et al, 1997], PHOBEA [Jaffe et al, 2001;Price et al, 2003], TRACE-P ], Trinidad Head , and ITCT 2K2 [Schauffler et al, 1999[Schauffler et al, , 2003]. …”

Gas‐phase chemical characteristics of Asian emission plumes observed during ITCT 2K2 over the eastern North Pacific Ocean

“…Previous work, both observational and theoretical, has studied the outflow of these emissions to the troposphere over western and central North Pacific [ Hoell et al , 1996, 1997; Huebert et al , 2003; Jacob et al , 2003; and references therein]. Observation‐based studies have reported the transport of these emissions to the eastern Pacific and western United States [ Parrish et al , 1992; Jaffe et al , 1999, 2001, 2003a, 2003b; Kotchenruther et al , 2001a; Moore et al , 2003; Price et al , 2003]. Additional studies suggest that emissions from Asia can affect tropospheric trace gas concentrations and photochemistry in the western United States.…”

Influence of long‐range‐transported pollution on the annual and diurnal cycles of carbon monoxide and ozone at Cheeka Peak Observatory

“…This will likely increase the amount of O 3 exported to North America [ Jacob et al , 1999; Yienger et al , 2000]. Numerous episodes of pollution of Asian origin have already been measured in the North Pacific and on the west coast of North America [ Jaffe et al , 1998, 1999, 2001, 2003a; Kotchenruther et al , 2001a; Price et al , 2003; Jaeglé et al , 2003]. However, to what extent these episodes control the background seasonality of O 3 and other pollutants like carbon monoxide (CO) in the boundary layer is still unclear.…”

“…Most previous measurements of O 3 and its precursors in the northeastern Pacific have only been made in the springtime (March–May) in part because of a higher probability of seeing long‐range transport compared to other seasons [ Jaffe et al , 1999, 2001; Newell and Evans , 2000; Kotchenruther et al , 2001a; Staudt et al , 2001; Price et al , 2003; Jaeglé et al , 2003; Huebert et al , 2003; Fuelberg et al , 2003]. This stems from relatively long lifetimes of O 3 and related species during spring and an increase in frontal activity in east Asia, whereby pollutants are lifted from the boundary layer for transport in the free troposphere [ Bey et al , 2001a; Liu et al , 2003; Jaeglé et al , 2003].…”