The following document provides a description of the scientific objectives, measurements, and implementation plan for the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) scheduled for early spring 2001. Related missions, PEM-West A and B, were conducted in 1991 and 1994, respectively. These missions are part of a continuing series of field studies that NASA has conducted over the past decade through its Global Tropospheric Experiment (GTE), a major component of the Tropospheric Chemistry Program within NASA's Earth Science Enterprise Office. Guidance for the GTE field studies has come from ad hoc planning meetings, convened by the Manager of the Tropospheric Chemistry Program. Emerging from the first of these planning meeting in July 1984 was a recommended long-range plan for a series of field studies to be conducted through the NASA Tropospheric Chemistry Program, and, where possible, coordinated with other national and international studies.

The recommended field measurements included studies of tropical forest, Arctic tundra, global distributions, long-range transport, as well as instrument intercomparisons. Since that initial meeting, four other planning meetings have been convened to review and update this long-range plan. The recommendations of these meetings have resulted in field studies of the Amazon Rain Forest and the northern latitude tundra (e.g. Atmospheric Boundary Layer Experiments, ABLE-2 and ABLE-3), evaluation of instrumentation for measurements of odd nitrogen and sulfur species (e.g. Chemical Instrumentation Test and Evaluation, CITE -2 and -3), measurements over the tropical Atlantic (e.g. Transport and Atmospheric Chemistry near the Equator- Atlantic, TRACE-A) and the current series of studies over the Pacific (e.g. Pacific Exploratory Missions, PEM-West A and B, PEM-Tropics A&B, and the current TRACE-P). The PEM experiments, along with TRACE-A and -P, are viewed as providing global distributions of key atmospheric species and studying their long-range transport.


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