Eulerian model evaluation field study (EMEFS): A summary of surface network measurements and data quality

From June 1988 to May 1990, a Joint Canada-United States measurement program known as EMEFS made daily air and precipitation measurements across eastern North America. Surface data were collected by five participating networks at approximately 130 sites for use in assessing regional air pollutant and deposition model performance. This paper describes the measurement program and focuses on its associated quality assurance program. The concentration measurements were found to have overall uncertainties of +/-2.3% for SO42- and NO3- for precipitation and, for the air concentrations, +/-6.4% for SO2, +/-5.4% for SO42-, and +/-10.3% for NO3-. These uncertainty levels generally satisfied the program data quality objectives for use in model evaluation studies and represent the quality of contemporary air precipitation chemistry networks.