An assessment of ozone photochemistry in the extratropical western North Pacific: Impact of continental outflow during the late winter/early spring

作者：J. H. Crawford, Douglas D. Davis, G. Chen, J. D. Bradshaw, S. T. Sandholm, Y. Kondo, Sutao Liu, E. V. Browell, G. Gregory, B. E. Anderson, G. W. Sachse, J. E. Collins, J. D. Barrick, D. R. Blake, R. W. Talbot, H. B. Singh · 发表于：Journal of Geophysical Research Atmospheres · 年份：1997 · DOI：10.1029/97jd02600 · 被引用次数：90 · 研究领域：Atmospheric Ozone and Climate、Atmospheric chemistry and aerosols、Atmospheric and Environmental Gas Dynamics

This study examines the influence of photochemical processes on tropospheric ozone distributions over the extratropical western North Pacific. The analysis presented here is based on data collected during the Pacific Exploratory Mission‐West Phase B (PEM‐West B) field study conducted in February‐March 1994. Sampling in the study region involved altitudes of 0–12 km and latitudes of 10°S to 50°N. The extratropical component of the data set (i.e., 20–50°N) was defined by markedly different photochemical environments north and south of 30°N. This separation was clearly defined by an abrupt decrease in the tropopause height near 30°N and a concomitant increase in total O 3 column density. This shift in overhead O 3 led to highly reduced rates of O 3 formation and destruction for the 30–50°N latitude regime. Both latitude ranges, however, still exhibited net O 3 production at all altitudes. Of special significance was the finding that net O 3 production prevailed even at boundary layer and lower free tropospheric altitudes (e.g., ≤ 4 km), a condition uncommon to Pacific marine environments. These results reflect the strong impact of continental outflow of O 3 precursors (e.g., NO and NMHCs) into the northwestern Pacific Basin. Comparisons with PEM‐West A, which sampled the same region in a different season (September‐October), revealed major differences at altitudes below 4 km, the altitude range most influenced by continental outflow. The resulting net rate of increase in the tro...