Transpacific transport of ozone pollution and the effect of recent Asian emission increases on air quality in North America: an integrated analysis using satellite, aircraft, ozonesonde, and surface observations

摘要

We use an ensemble of aircraft, satellite, sonde, and surface observationsfor April–May 2006 (NASA/INTEX-B aircraft campaign) to better understand themechanisms for transpacific ozone pollution and its implications for NorthAmerican air quality. The observations are interpreted with a global 3-Dchemical transport model (GEOS-Chem). OMI NO₂ satellite observationsconstrain Asian anthropogenic NO_x emissions and indicate a factor of 2increase from 2000 to 2006 in China. Satellite observations of CO from AIRSand TES indicate two major events of Asian transpacific pollution duringINTEX-B. Correlation between TES CO and ozone observations shows evidencefor transpacific ozone pollution. The semi-permanent Pacific High andAleutian Low cause splitting of transpacific pollution plumes over theNortheast Pacific. The northern branch circulates around the Aleutian Lowand has little impact on North America. The southern branch circulatesaround the Pacific High and some of that air impacts western North America.Both aircraft measurements and model results show sustained ozone productiondriven by peroxyacetylnitrate (PAN) decomposition in the southern branch,roughly doubling the transpacific influence from ozone produced in the Asianboundary layer. Model simulation of ozone observations at Mt. Bachelor Observatory in Oregon (2.7 km altitude) indicates a mean Asian ozonepollution contribution of 9±3 ppbv to the mean observed concentrationof 54 ppbv, reflecting mostly an enhancement in background ozone rather thanepisodic Asian plumes. Asian pollution enhanced surface ozone concentrationsby 5–7 ppbv over western North America in spring 2006. The 2000–2006 rise inAsian anthropogenic emissions increased this influence by 1–2 ppbv.