TESTING THE DAYTIME OXIDIZING CAPACITY OF THE TROPOSPHERE - 1994 OH FIELD CAMPAIGN AT THE IZANA-OBSERVATORY, TENERIFE

A field campaign was carried out during May 1994 at the Izana station, Tenerife. This campaign was part of the program Environment and Clima te sponsored by the European Commission to study tile influence of Eur opean emissions on the oxidizing capacity of a clean tropospheric envi ronment. Daytime and also nighttime measurements were made, covering t he OH as well as the NO3 chemistry. This paper presents the OH measure ments taken with a multipass optical absorption spectrometer (MOAS) an d discusses the daytime chemistry in a statistical and therefore more preliminary way. All relevant parameters influencing the OH concentrat ion were monitored. From the data the two main contributions to the OH production can clearly be discerned and are given by the primary prod uction following the ozone photolysis and the O(D-1)-H2O reaction and by the catalytic reactions of NOx in the recycling process. The latter processes prove to contribute a dominant part to the OH concentration . The measurements of the nonmethane hydrocarbons (NMHC) especially of the biogenics, indicate a considerable influence of the NMHC on the a bsolute values of the OH concentration at Tenerife.