Chemical composition of Asian continental outflow over the western Pacific: Results from Transport and Chemical Evolution over the Pacific (TRACE‐P)

Authors

R. S. Russo
R. W. Talbot
J. E. Dibb
E. Scheuer
G. Seid
C. E. Jordan
H. E. Fuelberg
G. W. Sachse
M. A. Avery
S. A. Vay
D. R. Blake
N. J. Blake
E. Atlas
A. Fried
S. T. Sandholm
D. Tan
H. B. Singh
J. Snow, University of Rhode Island
Brian G. Heikes, University of Rhode IslandFollow

Document Type

Article

Date of Original Version

2003

Department

Oceanography

Abstract

We characterize the chemical composition of Asian continental outflow observed during the NASA Transport and Chemical Evolution over the Pacific (TRACE‐P) mission during February–April 2001 in the western Pacific using data collected on the NASA DC‐8 aircraft. A significant anthropogenic impact was present in the free troposphere and as far east as 150°E longitude reflecting rapid uplift and transport of continental emissions. Five‐day backward trajectories were utilized to identify five principal Asian source regions of outflow: central, coastal, north‐northwest (NNW), southeast (SE), and west‐southwest (WSW). The maximum mixing ratios for several species, such as CO, C₂Cl₄, CH₃Cl, and hydrocarbons, were more than a factor of 2 larger in the boundary layer of the central and coastal regions due to industrial activity in East Asia. CO was well correlated with C₂H₂, C₂H₆, C₂Cl₄, and CH₃Cl at low altitudes in these two regions (r² ∼ 0.77–0.97). The NNW, WSW, and SE regions were impacted by anthropogenic sources above the boundary layer presumably due to the longer transport distances of air masses to the western Pacific. Frontal and convective lifting of continental emissions was most likely responsible for the high altitude outflow in these three regions. Photochemical processing was influential in each source region resulting in enhanced mixing ratios of O₃, PAN, HNO₃, H₂O₂, and CH₃OOH. The air masses encountered in all five regions were composed of a complex mixture of photochemically aged air with more recent emissions mixed into the outflow as indicated by enhanced hydrocarbon ratios (C₂H₂/CO ≥ 3 and C₃H₈/C₂H₆ ≥ 0.2). Combustion, industrial activities, and the burning of biofuels and biomass all contributed to the chemical composition of air masses from each source region as demonstrated by the use of C₂H₂, C₂Cl₄, and CH₃Cl as atmospheric tracers. Mixing ratios of O₃, CO, C₂H₂, C₂H₆, SO₂, and C₂Cl₄ were compared for the TRACE‐P and PEM‐West B missions. In the more northern regions, O₃, CO, and SO₂ were higher at low altitudes during TRACE‐P. In general, mixing ratios were fairly similar between the two missions in the southern regions. A comparison between CO/CO₂, CO/CH₄, C₂H₆/C₃H₈, NO_x/SO₂, and NO_y/(SO₂ + nss‐SO₄) ratios for the five source regions and for the 2000 Asian emissions summary showed very close agreement indicating that Asian emissions were well represented by the TRACE‐P data and the emissions inventory.

Citation/Publisher Attribution

Russo, R., et al. (2003), Chemical composition of Asian continental outflow over the western Pacific: Results from Transport and Chemical Evolution over the Pacific (TRACE‐P), J. Geophys. Res., 108, 8804, doi: 10.1029/2002JD003184, D20.

Available at: https://doi.org/10.1029/2002JD003184