Surface Ozone IN-SITU Measurements - Hourly Averages is historical digital data set DSI-3270, archived at the National Climatic Data Center (NCDC). DSI-3270 contains data from the Climate Monitoring Diagnostics Laboratory (CMDL), a part of the National Oceanic Atmospheric Administration's Environmental Research Laboratories (NOAA/ERL). CMDL does long-term monitoring of atmospheric trace ... constituents. One of these constituents is surface ozone hourly data. There are four baseline observatories maintained and operated by CMDL in widely separate locations where local pollution and anthropogenic influences are often non-existent. These sites are Barrow, Alaska; Mauna Loa Observatory, Hawaii; Cape Matatula, American Samoa; and South Pole, Antarctica. NCDC has historical data from 1973 or 1975 (depending on the station) to 1992. Ozone is measured continuously at these sites. DSI-3270 consists of one-hour average values of ozone.