Measurements of atmospheric trace gas concentrations during the field campaign in Jülich 1988

Our current understanding of the gas phase chemistry of the lower troposphere is based on measurements of trace gas concentrations in the atmosphere, laboratorystudies of gas phase reactions and model calculations of the relevant chemical processes. The ultimate validation of a reaction scheme can only be derived from acomparison of model results with experimental data from measurements in the atmosphere. In order to establish an extended and reliable experimental data set on which such a comparison could be based the Institut für Atmosphärische Chemie of the Forschungszentrum Jiilich (KFA) has been conducting field campaigns for a number of years. One such campaign took place in Jülich from May 9 - June 10 in 1988. Many of the relevant trace species were measured on a continuous basis together with photolysis frequencies and meteorological parameters. All measurements were ground based and included OH, O$_{3}$, NO, and NO$_{2}$, NO$_{y}$, HCHO, SO$_{2}$, CH$_{4}$, CO, non methane hydrocarbons up to C$_{5}$, peroxyacetylnitrate, and aldehydes. The photolysis frequencies of O$_{3}$ and NO$_{2}$ were also monitored, as were atmospheric temperature, relative humidity, wind speed, and wind direction. All quantities were measured in-situ except OH and SO$_{2}$, which were exclusively measured by a long path differential optical absorption technique. HCHO, NO$_{2}$, and O$_{3}$ were determined by in-situ and also by long-path-absorption methods for intercomparison. Jülich (lat.: 50.9°N, long.: 6.3°E, alt: 100 m) is a moderately polluted area about 5 km from motorways with heavy traffic and about 20 to 40 kna away from industrialized zones in the Rhine valley. The NO$_{x}$ mixing ratio showed large variability with a mean value of 9 ppb and 16- and 84-percentiles of 4 ppb and 22 ppb, respectively. The ozone concentration reached mean values of 24 ppb with peak values up to 84 ppb. The SO$_{2}$ burden was usually below 7.5 ppb with a mean concentration of 1.2 ppb. CO ranges from 200 ppb to 374 ppb (16- and 84-percentile) with an average concentration of 267 ppb and peak values up to 881 ppb. The measured average non methane hydrocarbon was 29 ppbC. All trace gases CH$_{4}$ showedsignificant diurnal variations. The trace gas scenario is typical for large parts of Germany (Umweltbundesamt, 1989). The paper describes the purpose and design of the campaign and presents diurnal profiles of all measured species in a first evaluation of the experimental material. A brief description of the experimental setup and an analysis of the experimental uncertainties are also given. The access to the data in computerized form for further interpretation and processing is indicated