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The second Pacific Exploratory Mission to the Tropics (PEM T‐B) was conducted as part of NASA's Global Tropospheric Experiment (GTE) from 25 February through 19 April 1999. Long‐range pollution signatures are examined during four PEM T‐B flights that ranged as far northeast as California and as far southwest as coastal New Guinea. The signatures are studied to determine their ages and chemical evolution during transport. The chemical species examined include nonmethane hydrocarbons, halocarbons, and carbon monoxide. Wind data from the European Centre for Medium Range Weather Forecasts (ECMWF) are used to calculate backward trajectories along the four flight tracks. Results show that some pollutants originating from the Asian continent, and even farther west, are transported across the Pacific by the middle latitude westerly winds and reach the subtropical Pacific anticyclone where they subside and turn southwestward under the influence of the low level trade winds. The parcels ultimately reach the western Pacific near coastal New Guinea after 20–25 days of transit.

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[1] Data from 10 aircraft programs recorded over the central/eastern North Pacific (180°-120°W, 0°-45°N) were assembled for the purpose of assessing an atmospheric chemical climatology for this region. It represents an early effort at carrying out this task and, thus, it can be expected to undergo many updates in the future. Such a database is useful in both gaining further insights concerning the fundamental processes controlling the chemistry of this region as well as serving as an important baseline by which to evaluate future change. Critical photochemical precursors examined included O 3 , CO, NO x , and H 2 O. In addition, the distribution profiles for select nonmethane hydrocarbons were explored. The precursor data were analyzed according to latitude, pressure altitude, and season of the year. Contrasting the spring and fall measurements, major trends that surfaced in both ozone and CO included observing elevated levels in spring compared to fall, with the largest spring increase occurring at latitudes north of 15°N. Both NO x and H 2 O showed trends quite different from that of CO and O 3 , with an indication of higher mixing ratio levels during the fall season. Variations in precursor distribution patterns within a season will be explained based on climatological flow patterns for the region and the resulting connection to source regions. Where possible, comparisons were performed with other sampling strategies, including ground-based observations, sonde, and satellite data, and data collected during shuttle missions. Overall, these comparisons revealed a reasonably high level of correspondence between the airborne ensemble data and those collected using other sampling strategies.

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