Global monitoring at the United States baseline stations with emphasis on precipitation chemistry measurements.

The National Oceanic and Atmospheric Administration Geophysical Monitoring for Climatic Change program has operated four remote precipitation chemistry stations at two polar and two tropical Pacific locations for over a decade. Station geography and meteorology is discussed and a summary of the hydrogen, sulfate, and nitrate ion data collected since 1980 is presented. Results show that at all four locations, the ions which have major anthropogenic sources were far less concentrated than in samples collected in heavily industrialized areas in the northeastern United States and Europe. Concentrations at American Samoa and the South Pole showed little variability over the year whereas concentrations at Point Barrow, Alaska and Mauna Loa, Hawaii were highly variable.